Effect of hydrogen peroxide on Na+,K+-ATPase activity in spermatozoa of infertile men

Abstract

Na+,K+-ATPase plays an essential role in sperm motility, hyperactivation, chemotaxis, acrosome reaction etc. Na+,K+-ATPase is sensitive to ROS insult. Apart from production of highly reactive molecules, H2O2 can exert a number of direct effects on cells, their metabolism and enzymes. In the present study, exposure to exogenous H2O2 was used to characterize the effects of H2O2 on Na+,K+-ATPase activity in spermatozoa of infertile men with different forms of pathospermia. It was shown that Na+,K+-ATPase activities in spermatozoa of infertile men with different forms of pathospermia were inhibited by exposure to H2O2 (50−500 μM). H2O2, one of the most toxic oxygen species, has the ability to depress Na+,K+-ATPase activity in a dose-dependent manner. Severe inhibition of the hydrolytic activity was observed when higher H2O2 were used. The time course of incubation with 100 μM H2O2 showed a sharp decrease in the enzyme activity during the first 5 min of incubation for both normozoospermic and pathozoospermic men. The enzymatic activity of Na+,K+-ATPase in the sperm was completely destroyed at 20 min for asthenozoospermic men and 30 min for normozoospermic men. We show that an administation of H2O2 inhibited Na+,K+-ATPase activity in normozoospermic samples with IC50 of 106.6 ± 7.9 μM. IC50 for patients with asthenozoospermia was two times less than for healthy men with preserved fertility. For other studied groups, the differences in IC50 were not significant. These observations suggest that Na+,K+-ATPase in pathozoospermic samples is more vulnerable to H2O2-induced damage than in normozoospermic men. The Hill coefficient was significantly increased only for patients with asthenozoospermia, indicating increased positively cooperative binding. The decreases in Na+,K+-ATPase hydrolase activity in H2O2-treated sperm cells in men with normozoospermia were largely attenuated by exogenous GSH at 5 mM. This suggests that GSH partially protects the Na+,K+-ATPase from inhibition under experimental oxidative stress. However, treatment of oligo-, astheno- and oligoasthenozoospermic samples with 100 μM H2O2 and 5 mM GSH did not result in protection of Na+,K+-ATPase against induced oxidation, suggesting that the impaired Na+,K+-ATPase in pathozoospermic samples appears to be an irreversible event. In contrast, presence of GSH only after H2O2 treatment does not reverse Na+,K+-ATPase inhibition. This study has provided a deeper insight into the role Na+,K+-ATPase plays in sperm cells,it also could offer clues to the clinical application of antioxidant therapy in male infertility therapy.