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°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.