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DNA damage in human sperm is highly correlated with oxidative stress

Date: 6-3-2009

De Iuliis GN, Thomson LK, Mitchell LA, Finnie JM, Koppers AJ, Hedges A, Nixon B, Aitken RJ

ARC Centre of Excellence in Biotechnology and Development and Hunter Medical Research Institute, Discipline of Biological Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia. Biol Reprod. 2009 Sep;81(3):517-24. Epub 2009 Jun 3

CONCLUSIONS:  DNA damage in human spermatozoa has been associated with a range of adverse clinical outcomes, including infertility, abortion, and disease in the offspring. These results seen in this study clearly highlight the importance of oxidative stress in the induction of sperm DNA damage and carry significant implications for the clinical management of this condition. 

DNA damage in human spermatozoa has been associated with a range of adverse clinical outcomes, including infertility, abortion, and disease in the offspring. We have advanced a two-step hypothesis to explain this damage involving impaired chromatin remodeling during spermiogenesis followed by a free radical attack to induce DNA strand breakage. The objective of the present study was to test this hypothesis by determining whether impaired chromatin predomination is correlated with oxidative base damage and DNA fragmentation in human spermatozoa. DNA fragmentation, chromatin protamination, mitochondrial membrane potential, and formation of the oxidative base adduct, 8-hydroxy-2'-deoxyguanosine (8OHdG), were monitored by flow cytometry/fluorescence microscopy. Impairment of DNA protamination during late spermatogenesis was highly correlated (P < 0.001) with DNA damage in human spermatozoa. The disruption of chromatin remodeling also was associated with a significant elevation in the levels of 8OHdG (P < 0.001), and the latter was itself highly correlated with DNA fragmentation (P < 0.001). The significance of oxidative stress in 8OHdG formation was demonstrated experimentally using H2O2/Fe2+ and by the correlation observed between this base adduct and superoxide generation (P < 0.001). That 8OHdG formation was inversely associated with mitochondrial membrane potential (P < 0.001) suggested a possible role for these organelles in the creation of oxidative stress. These results clearly highlight the importance of oxidative stress in the induction of sperm DNA damage and carry significant implications for the clinical management of this condition