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

Abstract

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 (H 2 O 2 ) 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 H 2 O 2 treatment. Furthermore, the three tests show a good correlation in revealing sperm with DNA strand breaks.

A cost for high levels of sperm competition in rodents: increased sperm DNA fragmentation

“…These results are in line with those previously reported in a study on spermatozoa of the laboratory mouse [35]. In that study [35], spermatozoa from mice, along with those of humans and bulls were exposed to concentrations of DNase-I and H 2 O 2 that were similar to the ones that we used.…”

“…These results are in line with those previously reported in a study on spermatozoa of the laboratory mouse [35]. In that study [35], spermatozoa from mice, along with those of humans and bulls were exposed to concentrations of DNase-I and H 2 O 2 that were similar to the ones that we used. Human and bull spermatozoa were found to be very sensitive to both DNase-I and H 2 O 2 , whereas mouse DNA spermatozoa were only moderately affected by the highest concentrations of those stressors.…”

“…Another aliquot was snap-frozen in liquid nitrogen, thawed at room temperature, vortexed during 10 s and snap-frozen again (vortex treatment). The remaining ten samples were exposed to different concentrations of DNase-I and H 2 O 2 , in line with the concentrations used for laboratory mouse spermatozoa in a previous study [35]. The use of these concentrations of DNase-I and H 2 O 2 provided the opportunity to directly compare our results with those of a previous comparative study on mammals [35].…”

“…The remaining ten samples were exposed to different concentrations of DNase-I and H 2 O 2 , in line with the concentrations used for laboratory mouse spermatozoa in a previous study [35]. The use of these concentrations of DNase-I and H 2 O 2 provided the opportunity to directly compare our results with those of a previous comparative study on mammals [35]. For the DNase-I treatment, five sperm aliquots in mT-H were centrifuged at 1677g (5000 r.p.m.…”

Dimethylnitrosamine-Induced Reduction in the Level of Poly-ADP-Ribosylation of Histone Proteins of Blood Lymphocytes - a Sensitive and Reliable Biomarker for Early Detection of Cancer

“…The structural integrity of the genomic DNA can be conveniently monitored by DNase I induced fragmentation of DNA (Apostolov et al, 2009). DNase I randomly cleave DNA, which is directly proportional to accessibility of the DNA to DNase I (Villani et al, 2010;Stephan et al, 2014). Therefore, if the DNA is in a condensed state, access of DNase I to DNA is limited and vice-versa.…”