Carcinogenesis Advance Access originally published online on August 2, 2006
Carcinogenesis 2007 28(1):207-214; doi:10.1093/carcin/bgl125
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Expression of human glutathione S-transferase P1 confers resistance to benzo[a]pyrene or benzo[a]pyrene-7,8-dihydrodiol mutagenesis, macromolecular alkylation and formation of stable N2-Gua-BPDE adducts in stably transfected V79MZ cells co-expressing hCYP1A1
1 Department of Biochemistry, Wake Forest University, School of Medicine, Medical Center Boulevard Winston-Salem NC, 27157, USA,
2 Department of Cancer Biology and Comprehensive Cancer Center, Wake Forest University, School of Medicine, Medical Center Boulevard Winston-Salem NC, 27157, USA,
3 James Graham Brown Cancer Center, University of Louisville School of Medicine Louisville, KY 40292, USA
4 Department of Pharmacology and Toxicology, University of Louisville School of Medicine Louisville, KY 40292, USA
5 GenPharmTox BioTech AG, Munich Germany
*To whom correspondence should be addressed. Tel: +336 713 7215; Fax: +336 716 7671; Email: atown{at}wfubmc.edu
Transgenic cell lines were constructed to study dynamic competition between activation versus detoxification of benzo[a]pyrene (B[a]P) and its metabolites. Transfected V79MZ cells expressing human cytochrome P4501A1 (hCYP1A1) alone, or expressing hCYP1A1 in combination with human glutathione S-transferase P1 (hGSTP1), were used to determine how effectively GST protects against macromolecular damage or mutagenicity of B[a]P or its enantiomeric dihydrodiol metabolites (+)-benzo[a]pyrene-7,8-dihydrodiol [(+)B[a]P-7,8-diol] and (–)-benzo[a]pyrene-7,8-dihydrodiol [(–)-B[a]P-7,8-diol]. Mutagenicity of B[a]P at the hprt locus was dose- and time-dependent in cells that expressed hCYP1A1. Mutagenicity was reduced in cells further modified to co-express hGSTP1. Dose-response and time-course studies indicated that mutagenicity was reduced up to 3-fold by hGSTP1 expression, compared with cells expressing hCYP1A1 alone. Mutagenicity induced by the B[a]P 7,8-dihydrodiols was also dose-dependent, and was reduced 2- to 5-fold by hGSTP1. Expression of hGSTP1 reduced B[a]P adducts in total cellular macromolecules by 3.8-fold, which correlated with the reduction in B[a]P mutagenicity and with reduction in the formation of the proximate metabolite B[a]P 7,8-dihydrodiols from B[a]P. However, measurement of total B[a]P metabolites bound to DNA isolated from cells incubated with [3H]-B[a]P revealed only 12, 33 and 24% reduction at 12, 24 and 48 h, respectively, by GSTP1 expression. Nevertheless, 32P-post-labeling analysis demonstrated nearly total prevention of the known B[a]P-DNA adduct, N2-guanine-benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), in cells co-expressing hGSTP1. This adduct, thought to be the most mutagenic of the stable B[a]P adducts, accounts for 15% or less of the total DNA adducts observed. These results indicate that the reduction in hCYP1A1-mediated B[a]P mutagenesis by hGSTP1 is probably largely due to prevention of the N2-guanine-BPDE adduct. However, the significant fraction (30–40%) of this mutagenesis and the majority of the total DNA binding that are not prevented together suggest formation by hCYP1A1 of a subset of mutagenic metabolites of B[a]P that are not effectively detoxified by hGSTP1.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  M. E. Kushman, S. L. Kabler, S. Ahmad, J. Doehmer, C. S. Morrow, and A. J. Townsend Protective Efficacy of hGSTM1-1 against B[a]P and (+)- or ( )-B[a]P-7,8-Dihydrodiol Cytotoxicity, Mutagenicity, and Macromolecular Adducts in V79 Cells Coexpressing hCYP1A1 Toxicol. Sci., September 1, 2007; 99(1): 51 - 57. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Tsai-Turton, B. N Nakamura, and U. Luderer Induction of Apoptosis by 9,10-Dimethyl-1,2-Benzanthracene in Cultured Preovulatory Rat Follicles Is Preceded by a Rise in Reactive Oxygen Species and Is Prevented by Glutathione Biol Reprod, September 1, 2007; 77(3): 442 - 451. [Abstract] [Full Text] [PDF]
|
|