BaP metabolism and DNA-adduct formation in cultured human lymphocytes treated in vitro with BaP and (-)-BaP-7,8-dihydrodiol

By Pavanello, S. - Zanesi, N. - Levis, A.G.

Nine samples of human lymphocytes from six healthy subjects were treated in vitro for 24 hours with [3H]-henzo[alpyrene (BaP) and unlabelled (-)-BaP-7,8-dihydrodiol; 1 microgram/ml and 0.5microgram/ml, respectively. The separation by HPLC of BaP-DNA adducts showed a significant formation of syn-BaPDE-dGuo adducts in five out of the nine human lymphocyte samples treated in vitro with [3H]-BaP. BaP-(7,10/8,9) tetrol and BaP-(7/8,9,10) tetrol derived from (+)-anti-BaPDE were the predominant isomers extracted from the culture medium of all the lymphocyte samples treated with (-)-BaP-7,8-dihydrodiol (mean ratio of anti-BaPDE/syn-BaPDE tetrols = 5.6 +/- 1.2), suggesting that the metabolic activation of (-)-Bap-7,8-dihydrodiol occurred by its epoxidation to (+)-anti-bapde much more frequently (4-8 times) than by epoxidation to the (-)-syn-bapde fonn. In contrast to the predominant formation of anti-BaPDE tetrols, the analysis by HPLC of DNA adducts in the five subjects examined also revealed the significant formation of syn-BaPDE-DNA adducts (mean adduct ratio of (+)-anti-/(-)-syn-BaPDE-DNA = 2.6 +/- 0.7). In six human lymphocyte samples treated in vitro with anti-BaPDE and syn-BaPDE, the anti-BaPDE bound to DNA 2-5 times more efficiently than did the syn-BaPDE. However, after 24 hours, the level of anti-BaPDE-DNA adducts significantly decreased almost to the level of the syn-BaPDE-DNA adducts, suggesting that a stereoselective repair mechanism could have preferentially removed the anti-BaPDE-DNA adducts.