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. 2007 Nov 1;624(1-2):80-7.
doi: 10.1016/j.mrfmmm.2007.04.004. Epub 2007 Apr 19.

Cytotoxicity and mutagenicity of dibenzo[a,l]pyrene and (+/-)-dibenzo[a,l]pyrene-11,12-dihydrodiol in V79MZ cells co-expressing either hCYP1A1 or hCYP1B1 together with human glutathione-S-transferase A1

Mary E Kushman  1 , Sandra L Kabler, Sarfaraz Ahmad, Johannes Doehmer, Charles S Morrow, Alan J Townsend
Affiliations

Cytotoxicity and mutagenicity of dibenzo[a,l]pyrene and (+/-)-dibenzo[a,l]pyrene-11,12-dihydrodiol in V79MZ cells co-expressing either hCYP1A1 or hCYP1B1 together with human glutathione-S-transferase A1

Mary E Kushman et al. Mutat Res. .

Abstract

We have used V79MZ hamster lung fibroblasts stably transfected with human cytochrome P450-1A1 (hCYP1A1; cell line designated V79MZh1A1) or P450-1B1 (hCYP1B1; cell line designated V79MZh1B1) alone, or in combination with human glutathione-S-transferase (GST) alpha-1 (hGSTA1), in order to examine GST protection against cytotoxicity and mutagenicity of dibenzo[a,l]pyrene (DBP) and the intermediate dihydrodiol metabolite (+/-)-DBP-11,12-dihydrodiol (DBPD). At comparable expression levels of hCYP1A1 and hCYP1B1, both DBP and DBPD were more cytotoxic in V79MZ1A1 (IC(50)=2.7 and 0.7nM, respectively) than in V79MZh1B1 (IC(50)=6.0 and 4.8nM, respectively). In contrast, both DBP and DBPD were two- to four-fold more mutagenic in V79MZh1B1 than in V79MZ1A1. Co-expression of hGSTA1 with hCYP1A1 decreased DBP cytotoxicity two-fold compared to V79MZh1A1 with hCYP1A1 alone, and provided a small, yet still statistically significant, 1.3-fold protection against DBPD. Protection against mutagenicity of these compounds was comparable to that for cytotoxicity in cells expressing hCYP1A1. In V79MZh1B1 cells, co-expression of hGSTA1 conferred up to five-fold protection against DBP cytotoxicity, and up to nine-fold protection against the (+/-)-DBP-dihydrodiol cytotoxicity relative to the cells expressing hCYP1B1 alone. Co-expression of hGSTA1 also reduced mutagenicity of DBP or its dihydrodiol to a lesser extent (1.3-1.8-fold) than the protection against cytotoxicity in cells expressing hCYP1B1. These findings demonstrate that the protective efficacy of hGSTA1 against DBP and DBPD toxicity is variable, depending on the compound or metabolite present, the specific cytochrome P450 isozyme expressed, and the specific cellular damage endpoint examined.

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Figures

Figure 1
Figure 1. Mutagenicity of DBP (Panel A) or (±)-DBP-11.12-dihydrodiol (Panel B) in the V79MZh1A1 cell line, with or without transfected hGSTA1-1
Solid bars, V79MZ control cells; gray bars, V79MZh1A1 cells (expressing hCYP1A1); open bars, V79MZh1A1/hGSTA1-39 (expressing both hCYP1A1 and hGSTA1). Results are the mean ± S.D. of at least three independent experiments.
Figure 1
Figure 1. Mutagenicity of DBP (Panel A) or (±)-DBP-11.12-dihydrodiol (Panel B) in the V79MZh1A1 cell line, with or without transfected hGSTA1-1
Solid bars, V79MZ control cells; gray bars, V79MZh1A1 cells (expressing hCYP1A1); open bars, V79MZh1A1/hGSTA1-39 (expressing both hCYP1A1 and hGSTA1). Results are the mean ± S.D. of at least three independent experiments.
Figure 2
Figure 2. Mutagenicity of DBP (Panel A) or (±)-DBP-11.12-dihydrodiol (Panel B) in the V79MZh1B1 cell line, with or without transfected hGSTA1-1
Solid bars, V79MZ control cells; gray bars, V79MZh1B1 cells (expressing hCYP1B1); open bars, V79MZh1B1/hGSTA1-11 (expressing both hCYP1A1 and hGSTA1). Results are the mean ± S.D. of at least three independent experiments.
Figure 2
Figure 2. Mutagenicity of DBP (Panel A) or (±)-DBP-11.12-dihydrodiol (Panel B) in the V79MZh1B1 cell line, with or without transfected hGSTA1-1
Solid bars, V79MZ control cells; gray bars, V79MZh1B1 cells (expressing hCYP1B1); open bars, V79MZh1B1/hGSTA1-11 (expressing both hCYP1A1 and hGSTA1). Results are the mean ± S.D. of at least three independent experiments.
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