Oxidative stress and sperm function
Increased lipid peroxidation, decreases sperm function.
Title: Aging: Impact of oxidative stress on human sperm function.
Abstract: Edna Tirado, Ming Zhang, David B. Brown, Naseem Ansari (The University of Texas Medical Branch, Galveston, TX & ReproSource Fertility Diagnostics.)
Objective: Oxidative stress is a result of an imbalance caused by: 1] over production of reactive oxygen species (ROS), and/or 2] reduced scavenger capacity. During aging the cellular antioxidant mechanisms downplay and create a situation of oxidative stress. High levels of ROS are believed to have detrimental effects on sperm function. We recently reported that when sperm from a fertile male was treated in vitro with ROS (50 and 100 μM H2O2), the ROS damaged sperm responded abnormally when analyzed in the human sperm activation assay (HSAA). The aim of this study was to determine the effect of oxidative stress as a possible agent that induces detrimental effects on sperm function correlating with lipid peroxidation and apoptosis.
Methodology: Semen sample was obtained in a sterile cup from fertile male by masturbation after 3 days of sexual abstinence and incubated at 37o C for 1 hour, to allow for complete liquefaction and then semen analysis was done according to world health organization criteria. Sperm was isolated from the seminal plasma using Percoll gradients and centrifugation at 1200 g for 15 minutes at room temperature. The sperm pellet from 80% was resuspended in phosphate buffered saline PBS, pH= 7.4, sperm concentration was determined and the sample was divided into 5 aliquots with the same sperm concentration and then treated as a follow PBS with H2O2 at concentrations of 0 μM untreated, and 10, 50, 100 and 500 μM. Following an incubation period, sperm were evaluated for determining (A) Lipid peroxidation by spectrophotometry, (B) Sperm function 1) viability, 2) motility 3) morphology, 3) acrosomal integrity, 4) hypo- osmotic swelling test (HOST) (C) Apoptosis.
Results: Linear regression analysis shows that lipid peroxidation is H2O2-dose dependent (r= 0.9128 p<0.001). To investigate whether lipid peroxidation or ROS production was the better predictor of human sperm function and apoptosis, the linear regression were calculated for each sperm function parameters, the results show that with increasing lipid peroxidation, sperm function was decreased. Oxidative stress induced morphological changes such as nuclear fragmentation, agglutination, chromatin dispersion and apoptosis. The number of abnormal sperm and apoptotic sperm were dose dependent, furthermore, with increasing lipid peroxidation, the number of abnormal sperm and under apoptosis were increased.
Conclusions: Human sperm exposed to oxidative stress are susceptible to oxygen-induced damage, which is mediated by lipid peroxidation leading to apoptosis and infertility. It therefore appears that age-related male infertility could be associated with oxidative stress.
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