Differences in aromatic-DNA adduct levels between alveolar macrophages and subpopulations of white blood cells from smokers

The 32P-post-labelling assay for DNA adduct quantification gives theopportunity to examine endogenous exposure to DNA reactive compounds. Mosthuman biomonitoring studies applied white blood cells (WBC) or cellsobtained by broncho-alveolar lavages (BAL) as source of DNA, but still itis not clear what cell type represents the most reliable indicator forexposure to cigarette smoke-associated genotoxins. At first, we examinedDNA adduct levels by means of nuclease P1 (NP1) enriched 32P-post-labellingin separated WBC subpopulations after in vitro incubations for 18 h with 10microM benzo[a]pyrene (B[a]P). DNA adduct levels were highest in monocytes(10.7 +/- 2.9 adducts/10(8) nucleotides, n = 8), followed by lymphocytes(5.9 +/- 1.7, n = 8), and granulocytes (0.5 +/- 0.2, n = 8). Secondly,aromatic-DNA adduct levels were determined in BAL cells and WBC-subsetsfrom (non-)smoking volunteers. In smoking individuals, adduct levels werein the ranking order: BAL cells (3.7 +/- 1.0, n = 5) > monocytes (2.0+/- 0.5, n = 8) > or = lymphocytes (1.6 +/- 0.4, n = 8) >granulocytes (0.8 +/- 0.2, n = 8) by NP1-enrichment and monocytes (9.0 +/-3.2, n = 5) > or = lymphocytes (8.0 +/- 2.1, n = 6) > granulocytes(2.1 +/- 0.3, n = 7) by butanol-enriched 32P-post-labelling. Aromatic-DNAadduct levels were significantly higher in WBC-subsets of smokers ascompared with non- smokers, except for DNA adducts in granulocytes usingbutanol enrichment. Thirdly, dose-response relationships were investigatedin mononuclear white blood cells (MNC, i.e. monocytes plus lymphocytes) andBAL-cells of a larger group of smoking individuals (n = 78). Adduct levelsin MNC were related to daily exposure to cigarette-tar (r = 0.31, P <0.01). Adduct levels in BAL cells seemed to be correlated with pack-years,but after correction for age this relationship was lost. Butanol extractionresulted in 5-6-fold higher DNA adduct levels in MNC, whereas butanolextraction of BAL-DNA of the same individuals yielded only 2-fold higheradduct levels. The two enrichment procedures of 32P-post-labelling werecorrelated in BAL cells (r = 0.86, P < 0.001, n = 12). We conclude thatparticularly MNC are good surrogates for the detection of smoking-relatedDNA adducts.