Hydroxyl radical-induced decline in motility and increase in lipid peroxidation and DNA modification in human sperm

We employed the xanthine-xanthine oxidase system to produce H2O2 or simply used commercially available H2O2 solution to investigate the effects of exogenous hydroxyl radicals on the motility characteristics and on lipid peroxidation and DNA modification of human sperm. The functional parameters of sperm motility declined concomitantly upon incubation of sperm with hydroxyl radicals. After incubation of freshly ejaculated human sperm with 0.23 mM H2O2 in the presence of 1.8 mM ADP and 2.7 mM FeSO4 for 1 hr at 37 degrees C, 90% reduction of motility was observed. Effect of hydroxyl radicals on sperm motility was dependent on the concentrations of FeSO4 and H2O2, respectively. The remaining motility of sperm after 1 hr incubation showed negative linear correlation with FeSO4 concentration. The response of sperm motility to FeSO4 was also dependent on the concentration of H2O2. Except for the amplitude of lateral head displacement, functional parameters of sperm declined with the increase of H2O2 concentration. Moreover, we found that lipid peroxidation measured as malondialdehyde (MDA) and accumulation of modified DNA indicated by 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in human sperm were significantly accelerated by exogenous hydroxyl radicals. The contents of lipid peroxides and 8-OH-dG in the spermatozoa were increased from 24.6 +/- 2.4 nmol MDA/1 x 10(7) sperm and 0.17 +/- 0.02% in the untreated group to 30.6 +/- 1.2 nmol MDA/1 x 10(7) sperm and 1.9 +/- 0.47%, respectively, in the sperm treated at 37 degrees C for 1 hr with 2.03 mM H2O2, 1.8 mM ADP and 4.5 mM FeSO4. Taken together, these results suggest that the detrimental effects of hydroxyl radicals on human sperm functions may be mediated, at least partly, through lipid peroxidation and DNA modification.