DNA adduct kinetics in reproductive tissues of DNA repair proficient and deficient male mice after oral exposure to benzo(a)pyrene

Abstract

Benzo(a)pyrene (B[a]P) can induce somatic mutations, whereas its potential to induce germ cell mutations is unclear. There is circumstantial evidence that paternal exposure to B[a]P can result in germ cell mutations. Since DNA adducts are thought to be a prerequisite for B[a]P induced mutations, we studied DNA adduct kinetics by 32 P-postlabeling in sperm, testes and lung tissues of male mice after a single exposure to B[a]P (13 mg/kg bw, by gavage). To investigate DNA adduct formation at different stages of spermatogenesis, mice were sacrificed at Day 1, 4, 7, 10, 14, 21, 32, and 42 after exposure. In addition, DNA repair deficient (Xpc 2/2 ) mice were used to study the contribution of nucleotide excision repair in DNA damage removal. DNA adducts were detectable with highest levels in lung followed by sperm and testis. Maximum adduct levels in the lung and testis were observed at Day 1 after exposure, while adduct levels in sperm reached maximum levels at 1 week after exposure. Lung tissue and testis of Xpc 2/2 mice contained significantly higher DNA adduct levels compared to wild type (Wt) mice over the entire 42 day observation period (P < 0.05). Differences in adduct half-life between Xpc 2/2 and Wt mice were only observed in testis. In sperm, DNA adduct levels were significantly higher in Xpc 2/2 mice than in Wt mice only at Day 42 after exposure (P 5 0.01). These results indicate that spermatogonia and testes are susceptible for the induction of DNA damage and rely on nucleotide excision repair for maintaining their genetic integrity. Environ. Mol. Mutagen. 51:123-129, 2010. V V C 2009 Wiley-Liss, Inc.

Tobacco consumption and benzo(a)pyrene-diol-epoxide–DNA adducts in spermatozoa: in smokers, swim-up procedure selects spermatozoa with decreased DNA damage

“…This technique also allows the study of small numbers of cells. In contrast, the 32P postlabeling assay is widely used to measure DNA adducts in sperm (9,21,22). That technique detects raw DNA adducts and requires careful interpretation of results if used on ex vivo samples of mixed cells.…”

“…Verhofstad et al (21) recently demonstrated in mice that spermatogonia are particularly sensitive to B[a]P-induced genotoxicity and that nucleotide excision repair is an important factor in maintaining the integrity of the genome. However, the capacity of germ cells to repair DNA damage is lost after meiosis (29).…”

Benzo[a]pyrene and Human Embryo

“…Changes in the DNA sequence can be induced by exposure to chemicals during life, but may also be inherited via mutations in the spermatogonial stem cells, in that way increasing the risk of developing abnormalities or diseases in the offspring (Vilarino-Guell et al, 2003). B[a]P related DNA damages were observed at all stages of spermatogenesis (Zenzes et al, 1999), which were associated with significantly decreased sperm counts (Verhofstad et al, 2009). …”

Benzo-a-pyrene induced genotoxicity and cytotoxicity in germ cells of mice: Intervention of radish and cress

“…The mutagenic potential of BaP in male germ cells, however, has still not been fully established. BaP-related DNA damage was observed at all stages of spermatogenesis and in testis [44,30], but it is largely unknown how germ cells deal with DNA damage to protect their genetic material, and to prevent the accumulation of mutations in the germ line [30]. However, there are dietary agents which have been found to be beneficial in promoting good health and reducing the carcinogenic risks associated with the exposure to some of these dietary agents [28,25].…”

“…The reactive intermediates of BaP metabolism also have the ability to alkylate nucleophilic sites of DNA [18,9], which can lead to the formation of basic sites and DNA strand breaks. Exposure to BaP can lead to structural changes in DNA of somatic cells and as a consequence to increase incidence of somatic diseases with a genetic basis [14,45] and [44]. The mutagenic potential of BaP in male germ cells, however, has still not been fully established.…”