Differences in aromatic-DNA adduct levels between alveolar macrophages and subpopulations of white blood cells from smokers |
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Authors: | Godschalk RW; Maas LM; Van Zandwijk N; van't Veer LJ; Breedijk A; Borm PJ; Verhaert J; Kleinjans JC; van Schooten FJ |
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Institution: | Department of Health Risk Analysis and Toxicology, Maastricht University, The Netherlands. |
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Abstract: | The 32P-post-labelling assay for DNA adduct quantification gives the
opportunity to examine endogenous exposure to DNA reactive compounds. Most
human biomonitoring studies applied white blood cells (WBC) or cells
obtained by broncho-alveolar lavages (BAL) as source of DNA, but still it
is not clear what cell type represents the most reliable indicator for
exposure to cigarette smoke-associated genotoxins. At first, we examined
DNA adduct levels by means of nuclease P1 (NP1) enriched 32P-post-labelling
in separated WBC subpopulations after in vitro incubations for 18 h with 10
microM benzoa]pyrene (Ba]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-subsets
from (non-)smoking volunteers. In smoking individuals, adduct levels were
in 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-DNA
adduct levels were significantly higher in WBC-subsets of smokers as
compared with non- smokers, except for DNA adducts in granulocytes using
butanol enrichment. Thirdly, dose-response relationships were investigated
in mononuclear white blood cells (MNC, i.e. monocytes plus lymphocytes) and
BAL-cells of a larger group of smoking individuals (n = 78). Adduct levels
in 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 extraction
resulted in 5-6-fold higher DNA adduct levels in MNC, whereas butanol
extraction of BAL-DNA of the same individuals yielded only 2-fold higher
adduct levels. The two enrichment procedures of 32P-post-labelling were
correlated in BAL cells (r = 0.86, P < 0.001, n = 12). We conclude that
particularly MNC are good surrogates for the detection of smoking-related
DNA adducts.
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