Evaluation of Benzo(a)pyrene-Induced Gene Mutations in Male Germ Cells (original) (raw)
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Scientific Reports
People are widely exposed to polycyclic aromatic hydrocarbons, like benzo[a]pyrene (BaP). Prior studies showed that prenatal exposure to BaP depletes germ cells in ovaries, causing earlier onset of ovarian senescence post-natally; developing testes were affected at higher doses than ovaries. Our primary objective was to determine if prenatal BaP exposure results in transgenerational effects on ovaries and testes. We orally dosed pregnant germ cell-specific EGFP-expressing mice (F0) with 0.033, 0.2, or 2 mg/kg-day BaP or vehicle from embryonic day (E) 6.5–11.5 (F1 offspring) or E6.5–15.5 (F2 and F3). Ovarian germ cells at E13.5 and follicle numbers at postnatal day 21 were significantly decreased in F3 females at all doses of BaP; testicular germ cell numbers were not affected. E13.5 germ cell RNA-sequencing revealed significantly increased expression of male-specific genes in female germ cells across generations and BaP doses. Next, we compared the ovarian effects of 2 mg/kg-day BaP...
BMC Genomics, 2010
Background Benzo [a]pyrene (B[a]P) exposure induces DNA adducts at all stages of spermatogenesis and in testis, and removal of these lesions is less efficient in nucleotide excision repair deficient Xpc -/- mice than in wild type mice. In this study, we investigated by using microarray technology whether compromised DNA repair in Xpc -/- mice may lead to a transcriptional reaction of the testis to cope with increased levels of B[a]P induced DNA damage. Results Two-Way ANOVA revealed only 4 genes differentially expressed between wild type and Xpc -/- mice, and 984 genes between testes of B[a]P treated and untreated mice irrespective of the mouse genotype. However, the level in which these B[a]P regulated genes are expressed differs between Wt and Xpc -/- mice (p = 0.000000141), and were predominantly involved in the regulation of cell cycle, translation, chromatin structure and spermatogenesis, indicating a general stress response. In addition, analysis of cell cycle phase dependent ...
Toxicology in vitro : an international journal published in association with BIBRA, 2007
Information on the metabolism of the environmental toxicant, benzo(a)pyrene (BaP) in the male reproductive system is crucial for understanding BaP-induced infertility. Microsomes were isolated from the liver and testes of rat, mouse, hamster, ram, boar, bull, and monkey and incubated with BaP. Post-incubation, samples were extracted with ethyl acetate and analyzed for BaP/metabolites by reverse-phase HPLC with fluorescence detection. A great variation among species to metabolize BaP was observed. The rodent testicular microsomes produced higher proportions of BaP 4,5-diol and 9,10-diol than did boar, ram, bull, and monkey. On the other hand, hepatic microsomes from higher mammals converted a greater proportion of BaP to 3-hydroxy and 9-hydroxy BaP, the detoxification products of BaP. Given the ability of BaP 7-8-diol 9, 10-epoxide, 3-, and 9-hydroxy BaP to bind with DNA and form adducts, there is a likelihood of risk arising from the accumulation of BaP metabolites in testicular tis...
The transgenerational impact of benzo(a)pyrene on murine male fertility
Human Reproduction, 2010
background: Benzo(a)pyrene (BaP) is an endocrine toxicant that is widely distributed in the environment. The adverse effects of BaP on fertility are well documented, however its effects on fertility in the subsequent generations are not known. We aimed to investigate the transgenerational effects of BaP on male fertility in mice.
Mutational spectra vary with exposure conditions: benzo[a]pyrene in human cells
Mutation research, 1996
The AHH-1 human lymphoblastoid line was exposed to benzo[a]pyrene under markedly different conditions: a single toxic exposure of 30 microM for 28 h, a nontoxic exposure of 0.5 microM for 6 days and an exposure approximating estimates of BP concentration in the human lung of 20 nM for 20 days. Duplicate cultures containing 2 x 10(9) cells each were used to assure the statistical quality of the mutational spectra. Point mutational hotspots were observed in bp 215 to 318 of the third exon of the hprt gene after mutants were selected en masse with 6-thioguanine, using a combination of denaturing gradient gel electrophoresis and high fidelity polymerase chain reaction. The spectra were highly reproducible in replicate experiments but varied dramatically among treatment conditions. These data demonstrate that mutational spectra were critically dependent upon conditions of exposure. The results significantly extend prior reports on this subject and clarify an important issue for the use o...
Environmental Toxicology, 2013
The objective of this study was to assess whether subchronic exposure to benzo(a)pyrene (BaP) via oral ingestion alter endpoints of the reproductive system of mice. Hsd: ICR (CD1) 10-week-old males (n 5 8) were randomly assigned to the exposure group and control group. Mice were administered BaP for 30 and 60 days by daily gavage at doses of 1, 10, 50, and 100 mg/kg body weight per day. At the end of the experiments, mice were anesthetized and reproductive organs, including testes, seminal vesicles, prostate, and cauda epididymis, were removed and examined. Spermatozoa quality and DNA strand breaks were assessed-1 and 10 mg/kg/day of BaP for 30 and 60 days did not significantly induce altered morphology or weights of testes, prostate, seminal vesicle, and epididymis, and spermatozoa quality of mice; 100 mg/kg/day of BaP for 60 days decreased weights of testes, seminal vesicle, and cauda epididymis. BaP exposure also significantly decreased motility, normal head morphology, vitality, and concentration of mature spermatozoa. In addition, BaP exposure induced a significant increase in DNA strand breaks.
Effects of Benzo[a]pyrene on Human Sperm Functions: An In Vitro Study
International Journal of Molecular Sciences
Benzo(a)pyrene (BaP) is considered one of the most dangerous air pollutants for adverse health effects, including reproductive toxicity. It is found both in male and female reproductive fluids likely affecting spermatozoa after the selection process through cervical mucus, a process mimicked in vitro with the swim-up procedure. In vitro effects of BaP (1, 5, 10 µM) were evaluated both in unselected and swim-up selected spermatozoa after 3 and 24 h of incubation. BaP reduced total, progressive and hyperactivated motility and migration in a viscous medium both in swim-up selected and unselected spermatozoa. Viability was not significantly affected in swim-up selected but was reduced in unselected spermatozoa. In swim-up selected spermatozoa, increases in the percentage of spontaneous acrosome reaction and DNA fragmentation were observed after 24 h of incubation, whereas no differences between the control and BaP-treated samples were observed in caspase-3 and -7 activity, indicating no...
Human T-lymphocytes have been treated with benzo[a]pyrene diolepoxide (BPDE) in vitro and T-cell clones mutated in the hprt gene have been isolated. The mutant frequencies in BPDE-treated T-cell cultures were on average 24-fold higher than those of untreated cultures. Thus, BPDE is a potent inducer of gene mutation in this system. In order to examine which types of mutations are induced by BPDE in human cells, 41 spontaneous and 44 BPDE-induced mutant clones have been characterized using the Southern blot technique. In addition, rearrangements of the T-cell-receptor fl and 7 loci have been used to determine the proportion of isolated clones that are unique, and thus likely to represent independent mutational events. Out of 23 independent spontaneous mutants 4 had large hprt alterations that could be detected on Southern blots. Two of these alterations, deletions of exons 2-6, have been confirmed using PCR of hprt cDNA and direct sequencing of the PCR product. All 33 independent BPDE-induced mutants had normal hprt restriction patterns which indicates that BPDE is mainly a point mutagen in this system. Polycyclic aromatic hydrocarbons (PAH's) are common in the environment and include many mutagenic and carcinogenic compounds . The best studied PAH is benzo[a]pyrene. In mammalian cells, benzo[a]pyrene is metabolized to a variety of different compounds including 7,8-di-
Mutagenesis, 2010
Exposure to genotoxins may compromise DNA integrity in male reproductive cells, putting future progeny at risk for developmental defects and diseases. To study the usefulness of sperm DNA damage as a biomarker for genotoxic exposure, we have investigated cellular and molecular changes induced by benzo[a]pyrene (B[a]P) in human sperm in vitro, and results have been compared for smokers and non-smokers. Sperm DNA obtained from five smokers was indeed more fragmented than sperm of six non-smokers (mean % Tail DNA 26.5 and 48.8, respectively), as assessed by the alkaline comet assay (P < 0.05). B[a]P-related DNA adducts were detected at increased levels in smokers as determined by immunostaining. Direct exposure of mature sperm cells to B[a]P (10 or 25 mM) caused moderate increases in DNA fragmentation which was independent of addition of human liver S9 mix for enzymatic activation of B[a]P, suggesting some unknown metabolism of B[a]P in ejaculates. In vitro exposure of samples to various doses of B[a]P (with or without S9) did not reveal any significant differences in sensitivity to DNA fragmentation between smokers and non-smokers. Incubations with the proximate metabolite benzo[a]pyrener-7,t-8-dihydrodiol-t9,10-epoxide (BPDE) produced DNA fragmentation in a dose-dependent manner (20 or 50 mM), but only when formamidopyrimidine DNA glycosylase treatment was included in the comet assay. These levels of DNA fragmentation were, however, low in relation to very high amounts of BPDE-DNA adducts as measured with 32 P postlabelling. We conclude that sperm DNA damage may be useful as a biomarker of direct exposure of sperm using the comet assay adapted to sperm, and as such the method may be applicable to cohort studies. Although the sensitivity is relatively low, DNA damage induced in earlier stages of spermatogenesis may be detected with higher efficiencies.