Expression of CYP1A1, CYP1B1 and CYP3A, and polycyclic aromatic hydrocarbon-DNA adduct formation in bronchoalveolar macrophages of smokers and non-smokers

Variability in the expression of enzymes metabolizing carcinogens derived f rom cigarette smoke may contribute to individual susceptibility to pulmonar y carcinogenesis. This study was designed to determine the effects of smoki ng and 3 major cytochrome P450 (CYP) enzymes, i,e, CYPIAI, CYPIBI and CYP3A , which metabolize polycyclic aromatic hydrocarbons (PAH) on PAH-DNA adduct formation in the bronchoalveolar macrophages (BAM) of 31 smokers and 16 no n-smokers. CYP protein levels were determined by immunoblotting and PAH-DNA adduct levels by the nuclease PI enhanced P-32-postlabeling method. The ex pression of specific CYP forms was confirmed by reverse transcriptase-polym erase chain reaction (RT-PCR) from 10 additional samples. CYP3A protein, CY P3A5 by RT-PCR, was detected in the majority of samples from smokers and no n-smokers, The levels of CYP3A appeared Co be lower in active smokers than in ex-smokers (p = 0.10) or never smokers (p = 0,02), CYP IAI was not detec table by either immunoblotting or RT-PCR, The expression of CYP IBI was low or undetectable in most samples. The PAH-DNA adduct levels were higher(mea n 1.57/10(8) nucleotides) in samples from smokers compared with non-smokers (mean 0.42/10(8) nucleotides, p < 0.001) and the number of adducts correla ted with the number of cigarettes smoked daily (regression analysis, P < 0. 001), Higher levels of adducts were detected in samples from smokers with a high level of CYP3A compared with those with a low level (regression analy sis, p = 0,002), As CYP3A5 is abundant: in both lung epithelial cells and B AM, its association with adduct formation suggests that this CYP form may b e important in the activation of cigarette smoke procarcinogens, (C) 2000 W iley-Liss, Inc.