Patrizia Eleuteri

Exposure to PCBs and p,p′-DDE and human sperm chromatin integrity

Persistent organochlorine pollutants (POPs) such as polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (p,p′-DDE), the major metabolite of dichlorodiphenyltrichloroethane (DDT), are stable lipophilic compounds widely found in the environment and in the general population. They can enter the food chain, and their negative impact on male reproduction is currently under active scrutiny. To explore the hypothesis that environmental exposure to these compounds is associated with altered sperm chromatin structure integrity in human sperm, we conducted a study of 176 Swedish fishermen (with low and high consumption of fatty fish, a very important exposure source of POPs). We determined serum levels of 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153) and p,p′-DDE, and we used the sperm chromatin structure assay (SCSA) to assess sperm DNA/chromatin integrity. When CB-153 serum levels (individual dose range, 39–1,460 ng/g lipid) were categorized into equally sized quintiles, we found an association with the DNA fragmentation index (%DFI). A significantly lower %DFI was found in the lowest CB-153 quintile (< 113 ng/g lipid) compared with the other quintiles; there was a similar tendency, although not statistically significant, between %DFI and p,p′-DDE. These results suggest that POP exposure may have a slight negative impact on human sperm chromatin integrity.

Sperm DNA fragmentation induced by DNAse I and hydrogen peroxide: an in vitro comparative study among different mammalian species.

Sperm DNA damage may have adverse effects on reproductive outcome. Sperm DNA breaks can be detected by several tests, which evaluate DNA integrity from different and complementary perspectives and offer a new class of biomarkers of the male reproductive function and of its possible impairment after environmental exposure. The remodeling of sperm chromatin produces an extremely condensed nuclear structure protecting the nuclear genome from adverse environments. This nuclear remodeling is species specific, and differences in chromatin structure may lead to a dissimilar DNA susceptibility to mutagens among species. In this study, the capacity of the comet assay in its two variants (alkaline and neutral) to detect DNA/chromatin integrity has been evaluated in human, mouse, and bull sperm. The hypothesis that chromatin packaging might influence the amount of induced and detectable DNA damage was tested by treating sperm in vitro with DNAse I, whose activity is strictly dependent upon its DNA accessibility. Furthermore, hydrogen peroxide (H2O2) was used to assess whether spermatozoa of the three species showed a different sensitivity to oxidative stress. DNAse I-induced damage was also assessed by the sperm chromatin structure assay and the TUNEL assay, and the performances of these two assays were compared and correlated with the comet assay results. Results showed a different sensitivity to DNAse I treatment among the species with human sperm resulting the most susceptible. On the contrary, no major differences among species were observed after H2O2 treatment. Furthermore, the three tests show a good correlation in revealing sperm with DNA strand breaks.

Toxic and genotoxic effects of oral administration of furan in mouse liver

In this study, the effects induced in mouse liver by repeated oral exposure to furan were investigated. To this aim, the compound was given for 28 days by daily gavage to male B6C3F1 mice at 2, 4, 8 and 15 mg/kg body weight (b.w.)/day. Twenty-four hours after last administration, animals were sacrificed, liver was excised and the following parameters were evaluated: histological alterations, apoptosis, cell proliferation, polyploidy, overall DNA methylation, gene expression and DNA damage by the immunofluorescence detection of foci of phosphorylated histone H2AX (gamma-H2AX) and by alkaline comet assays, using both standard and modified protocols for the detection of DNA cross links. Liver DNA damage by comet assays was also evaluated in mice receiving furan as a single acute oral dose (15, 100 or 250 mg/kg b.w.). Microscopic analysis of liver sections indicated that repeated oral administration of furan was moderately toxic, producing mild histological alterations with necrotic figures, apoptosis and limited regenerative cell proliferation. The flow cytometric analysis of DNA content in single-cell suspensions of liver cells showed a statistically significant increase in polyploid (8N) cells at the highest dose. No treatment-related changes in overall DNA methylation, gamma-H2AX foci, DNA strand breaks and cross links were observed at the end of the 4-week exposure period. However, several genes involved in DNA damage response, beyond stress and liver toxicity, were over-expressed in mice treated with the highest furan dose (15 mg/kg b.w./day). Acute administration of furan induced evident liver toxicity at the highest dose (250 mg/kg b.w.), which was associated with a significant increase of DNA damage in the alkaline comet assay and with a distinct decrease in gamma-ray-induced DNA migration. Overall, the results obtained suggest that the contribution of genotoxicity to the mechanism of furan carcinogenicity in mouse liver should not be dismissed.

Kinetics of γ-H2AX induction and removal in bone marrow and testicular cells of mice after X-ray irradiation

Male germ cells have been shown to differ in their DNA damage response (DDR) with respect to somatic cells. In addition, DDR pathways are modulated along spermatogenesis, accompanying profound chromatin modifications. Histone H2AX phosphorylation is a fundamental step of DDR. Few data are available on the long-term kinetics of phosphorylated H2AX (γ-H2AX) after in vivo irradiation. We have investigated, by microscopic and flow cytometric immunochemistry, γ-H2AX induction and removal in testicular cells of irradiated mice, in comparison with bone marrow cells. In unirradiated testicular cells, much higher levels of γ-H2AX were measured by flow cytometry with respect to bone marrow cells. Irradiation induced a redistribution of γ-H2AX into discrete foci detectable by microscopy. In irradiated bone marrow, the percentage of labelled cells peaked at 1 h and rapidly declined, in agreement with data on in vitro cell lines. In contrast, spermatocytes and round spermatids showed persistent labelling until 48 h. During this time, in spermatids, topological changes were observed in γ-H2AX foci from a pattern of many uncountable dots to a pattern of few large spots. Observations of testicular sections confirmed this trend in the reduction of foci number in spite of substantially invariable percentages of labelled cells in the analysed timeframe. To assess whether γ-H2AX persistence in testicular cells was due to unrepaired DNA breaks, we performed comet assay and immunofluorescence analysis of Mdc1, a marker of DDR different from γ-H2AX. Comet assay showed that most breaks were repaired within 2 h. Forty-eight hours after irradiation, contrary to γ-H2AX foci that remained detectable in 80% of initially labelled cells, Mdc1 foci were observed in only 20-30% of cells. These data suggest that, at long times after irradiation, mechanisms additional to impairment of DNA break repair may account for the long persistence of γ-H2AX foci in male germ cells.

No genotoxicity in rat blood cells upon 3- or 6-month inhalation exposure to CeO2 or BaSO4 nanomaterials.

In the course of a 2-year combined chronic toxicity—carcinogenicity study performed according to Organisation for Economic Co-operation and Development (OECD) Test Guideline 453, systemic (blood cell) genotoxicity of two OECD representative nanomaterials, CeO2 NM-212 and BaSO4 upon 3- or 6-month inhalation exposure to rats was assessed. DNA effects were analysed in leukocytes using the alkaline Comet assay, gene mutations and chromosome aberrations were measured in erythrocytes using the flow cytometric Pig-a gene mutation assay and the micronucleus test (applying both microscopic and flow cytometric evaluation), respectively. Since nano-sized CeO2 elicited lung effects at concentrations of 5mg/m3 (burdens of 0.5mg/lung) in the preceding range-finding study, whereas nano-sized BaSO4 did not induce any effect, female rats were exposed to aerosol concentrations of 0.1 up to 3mg/m3 CeO2 or 50mg/m3 BaSO4 nanomaterials (6h/day; 5 days/week; whole-body exposure). The blood of animals treated with clean air served as negative control, whereas blood samples from rats treated orally with three doses of 20mg/kg body weight ethylnitrosourea at 24h intervals were used as positive controls. As expected, ethylnitrosourea elicited significant genotoxicity in the alkaline Comet and Pig-a gene mutation assays and in the micronucleus test. By contrast, 3- and 6-month CeO2 or BaSO4 nanomaterial inhalation exposure did not elicit significant findings in any of the genotoxicity tests. The results demonstrate that subchronic inhalation exposure to different low doses of CeO2 or to a high dose of BaSO4 nanomaterials does not induce genotoxicity on the rat hematopoietic system at the DNA, gene or chromosome levels.

The usefulness of combining traditional sperm assessments with in vitro heterospermic insemination to identify bulls of low fertility as estimated in vivo

To date, no single in vitro assessment can estimate bull fertility. This research was aimed at evaluating the ability of a series of laboratory assessments to assign 50 Holstein Friesian bulls grouped as low (ER-NRR<-1.5), medium (-0.5<ER-NRR<+0.5) and high (ER-NRR≥+1.5) fertility based on estimated relative non-return rates (ER-NRR), to the two categories of low and medium-high fertility. Heterospermic insemination with a Piedmontese reference bull was employed to define an index of competitive binding ability (CBI) to the zona pellucida using fluorochrome-labeled sperm, and a competitive fertility index (CFI) using embryo paternal assignment by single nucleotide polymorphism (SNP). Furthermore, kinetic parameters, membrane integrity and sperm DNA/chromatin integrity (% DFI) were assayed. Low fertility bulls had lesser (P<0.05) values for total motility and membrane integrity, and a greater value of % DFI as compared to medium and high fertility groups. A modest (P<0.001) correlation was reported among ER-NRR and total motility (r=0.30), progressive motility (r=0.26), membrane integrity (r=0.43) and % DFI (r=-0.26). While % DFI alone allowed the identification of 70% lowly fertile bulls, combining membrane integrity, average path velocity and CBI allowed for identification of 78% of the lowly fertile sires. Paternal assignment by SNPs resulted in 96% of successful assignments and could provide an alternative support to microsatellites for in vivo studies based on heterospermic fertilization for estimating fertility.

Direct and Delayed X-Ray-Induced DNA Damage in Male Mouse Germ Cells

Sperm DNA integrity is essential for the accurate transmission of paternal genetic information. Various stages of spermatogenesis are characterized by large differences in radiosensitivity. Differentiating spermatogonia are susceptible to radiation‐induced cell killing, but some of them can repair DNA damage and progress through differentiation. In this study, we applied the neutral comet assay, immunodetection of phosphorylated H2AX (γ‐H2AX) and the Sperm Chromatin Structure Assay (SCSA) to detect DNA strand breaks in testicular cells and spermatozoa at different times following in vivo X‐ray irradiation. Radiation produced DNA strand breaks in testicular cells that were repaired within the first few hours after exposure. Spermatozoa were resistant to the induction of DNA damage, but non‐targeted DNA lesions were detected in spermatozoa derived from surviving irradiated spermatogonia. These lesions formed while round spermatids started to elongate within the testicular seminiferous tubules. The transcription of pro‐apoptotic genes at this time was also enhanced, suggesting that an apoptotic‐like process was involved in DNA break production. Our results suggest that proliferating spermatogonia retain a memory of the radiation insult that is recognized at a later developmental stage and activates a process leading to DNA fragmentation. Environ. Mol. Mutagen. 2012.

Exposure to Perfluoroalkyl Substances and Sperm DNA Global Methylation in Arctic and European Populations

Perfluoroalkyl substances (PFASs) are widely used in a variety of industrial processes and products, and have been detected globally in humans and wildlife. PFASs are suspected to interfere with endocrine signaling and to adversely affect human reproductive health. The aim of the present study was to investigate the associations between exposure to PFASs and sperm global methylation levels in a population of non‐occupationally exposed fertile men. Measurements of PFASs in serum from 262 partners of pregnant women from Greenland, Poland and Ukraine, were also carried out by liquid chromatography tandem mass spectrometry. Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) were detected in 97% of the blood samples. Two surrogate markers were used to assess DNA global methylation levels in semen samples from the same men: (a) average DNA methylation level in repetitive DNA sequences (Alu, LINE‐1, Satα) quantified by PCR‐pyrosequencing after bisulfite conversion; (b) flow cytometric immunodetection of 5‐methyl‐cytosines. After multivariate linear regression analysis, no major consistent associations between PFASs exposure and sperm DNA global methylation endpoints could be detected. However, since weak but statistically significant associations of different PFASs with DNA hypo‐ and hyper‐methylation were found in some of the studied populations, effects of PFASs on sperm epigenetic processes cannot be completely excluded, and this issue warrants further investigation. Environ. Mol. Mutagen. 55:591–600, 2014.

Sex Identification in the Egyptian Vulture by Flow Cytometry and Cytogenetics

The genome size and sex of the Egyptian Vulture (Neophron percnopterus), a sexually monomorphic bird, were identified from blood samples by the use of flow cytometry (FCM). This technique allowed evaluation of the slightly higher amount of DNA content in the homogametic male compared to that of the heterogametic female. A karyotypic analysis also was performed in order to confirm the FCM results. Sex identification by both FCM and cytogenetic analyses was concordant in all cases. The average DNA content was estimated to be 5.6% higher in males than in females.

Bladder Transitional Cell Carcinomas: A Comparative Study of Washing and Tumor Bioptic Samples by DNA Flow Cytometry and FISH Analyses

Objective and Methods: We compared information obtained from samples of tumor biopsy and bladder washing to evaluate the representatives of the latter type of sampling. Both types of samples from 44 cases of superficial bladder TCCs and one papilloma were analyzed by FCM, to evaluate cellular DNA content, and FISH, to detect numerical aberration of chromosome 9. Results: The use of both tumor and washing samples by FCM and FISH analyses evidenced alterations in 95% of cases. FCM evidenced higher aneuploid frequency in bladder washing than in bioptic specimens. In bladder washing, FISH analysis showed higher frequency of monosomy and lower frequency of trisomy than in biopsy. No correlation was found between histological grade and centromeric chromosome 9 loss while correlation was evidenced with centromeric 9 gain. Conclusion: Irrigation specimens, analyzed by FCM and FISH, can complement information obtained by biopsy in cytodiagnosis and follow–up of patients with bladder TCC.