I-15: Effects of Oxidative Stress on Sperm Function

Semen analysis is the frontline and old reliable test in the assessment of male fertility, but it failed to provide absolute prediction of sperm function and its fertilizing ability. A wide variety of internal and external factors affect sperm function without discernible and significant effects on semen analysis. Oxygen toxicity and oxidative stress (OS) are inherent challenge of living cells such as spermatozoa under aerobic conditions. It is proved that OS affects sperm function and has a key role in the etiology of male infertility. A wide range of exogenous factors such as culture media, oxygen tension, metal ions, pollutants, temperature, visible light and also defective Spermatozoa and leukocytes are potentially sources of reactive oxygen species (ROS) and subsequently OS. OS impairs sperm function through inducing lipid peroxidation, DNA fragmentation and apoptosis. Lipid composition of sperm membrane is susceptible to peroxidation and consequently failures of membrane structure and function (ions and metabolites transport and gradient, signal transduction). ROS significantly increase DNA damage in the form of changes in all bases, creation of base-free sites, deletions, frame shifts, DNA cross-links and chromosomal arrangements. Spermatozoa show a lot of apoptosis features such as activation of caspases 1, 3, 8, and 9, annexin-V binding. Exposure of human spermatozoa to ROS triggers apoptosis process through caspase 3 activity. Thus the above effects of OS are demonstrated as asthenozospermia, teratozoospermia, and apoptotic spermatozoa that accompany with poor to failed fertilization and embryo development, repeated ART failures and recurrent pregnancy loss. OS can be overcome through many strategies such as antioxidant supplementation, treatment and prevention of pathogenesis result to OS, change in life style, in vitro culture under low oxygen tension and several other strategies. Finally measurement of OS markers is under sever inter and intra-laboratory variations. Therefore an integrated method with comprehensive measurement of the OS markers should be devised in future.