Glutathione S-transferases and aromatic DNA adducts in smokers' bronchoalveolar macrophages

Interindividual differences in the expression of carcinogen-metabolizing enzymes in the lung may modify the effective dose of tobacco carcinogens in this organ. We investigated the role of detoxifying glutathione S-transferases (GST) in the formation of aromatic DNA adducts in bronchoalveolar macrophages (BAM) of active smokers. The effect of GSTs on aromatic DNA adducts was studied separately and in combination with the PAH-metabolizing cytochrome P450 enzyme, CYP3A. GSTA, GSTM3, GSTP, and CYP3A protein levels were analyzed by Western blotting, GSTM1 and GSTP1 genotypes were determined by polymerase chain reaction (PCR) based methods, and numbers of aromatic DNA adducts were measured by nuclease P1 enhanced 32P-postlabeling method in BAM of 31 active smokers. No correlation was observed between GSTA or GSTP proteins or GSTM1 or GSTP1 genotypes and the level of aromatic DNA adducts. A high or medium expression level of GSTM3 was associated with a lower level of aromatic DNA adducts in the smokers who smoked less than 20 cigarettes per day, when the effect of GSTM3 was analyzed in combination with CYP3A (regression analysis; F(6,24)=6.3, P<0.001). No protection by GSTM3 was observed in heavy smokers. High CYP3A levels, on the other hand, increased the number of DNA adducts regardless of the amount of smoking.