Abstract

Infertility is a clinical disorder affecting approximately 15% of reproductive-aged couples worldwide. Recently, the influence of oxidative stress (OS) in decreased semen quality has been discussed. OS corresponds to an imbalance between oxidants and antioxidants defenses, present in the organism. High levels of reactive oxygen species (ROS) damage biomolecules present in sperm cells and may lead to the loss of membrane integrity, DNA fragmentation or even to death by apoptosis. This study aimed to evaluate the correlation between human semen clinic parameters and parameters that assessed the presence of OS. A total of 32 semen samples, obtained from a randomized group of donors, were included in this study. Basic semen parameters were analyzed according to the WHOs guidelines. The total antioxidant capacity of sperm cells was measured as well as the expression of certain antioxidant proteins, namely superoxide dismutase (SOD) and glutathione peroxidase 4 (GPx4), by colorimetric techniques and immunoblotting, respectively. The effect of ROS in spermatozoa protein oxidation was analyzed by determining the presence of 3-nitrotyrosine and carbonyl groups, by slot blot. Lipid peroxidation was evaluated, by performing the thiobarbituric acid reactive substances (TBARS) assay with colorimetric tests. The results indicated that SOD was negatively correlated with viscosity (p = 0.035), volume (p = 0.004) and carbonyl groups presence (p = 0.005). This protein also showed a positive correlation with the presence of tail defects in sperm cells (p = 0.044). In turn, GPx4 showed a negative correlation with the presence of non-progressive motile spermatozoa (p = 0.012). TBARS assay revealed a negative correlation with the concentration of sperm cells (p = 0.000) and the total number of spermatozoa (p = 0.026), but, in turn, this assay showed a positive correlation with the volume of semen (p = 0.038). It was concluded that the seminal quality is affected by the oxidative balance in sperm cells. The obtained results suggest that lipid peroxidation leads to a reduction in sperm concentration, antioxidant proteins protect the spermatozoa against protein oxidation and contribute to an increased sperm motility and normal semen viscosity. Thus, evaluation of oxidative parameters may be a useful tool for male infertility diagnosis and follow-up of antioxidant treatments.