Alpha-Tocopherol Stimulates Motility, Capacitation and Survival of Human Sperm

Human sperm produce reactive oxygen species (ROS) during mitochondrial respiration in low amounts required for various signaling pathways. The production of physiological ROS in sperm cells can regulate important functional characteristics such as motility, capacitation, acrosome reactions, hyperactivation, and sperm-oocyte fusion. However, excess ROS can have detrimental effects. In previous studies, it has been reported that ?-tocopherol can improve motility and protect sperm from the harmful effects of oxidative stress. However, the molecular mechanism of this effect is still unclear. This study aimed to analyze the effects of ?-tocopherol on sperm lipid peroxidation, motility, capacitation, and cell survival. After incubation for 2 hours with various concentrations of ?-tocopherol, sperm motility was checked using a computer-assisted sperm analyzer (CASA), ROS was measured with MDA levels, sperm membrane integrity was checked using a hypo-osmotic swelling test, while capacitation, cell survival, and apoptosis were checked using western immunoblotting. Results showed that ?-tocopherol does not affect MDA levels in sperm cells. However, in other parameters, the addition of ?-tocopherol improves sperm motility, membrane integrity, and tyrosine phosphorylation. ?-Tocopherol also has a positive effect on sperm survival, as demonstrated by increased phosphorylation of Akt and decreased expression of caspase-3 in sperm cells. ?-Tocopherol does not affect the lipid peroxidation of the sperm cell membrane, but it does improve membrane integrity and stimulate the motility, capacitation, and survival of human sperm cells.