Oxidative stress and male infertility: role of antioxidants and their possible applications in assisted reproduction

Low levels of reactive oxygen species (ROS) are essential for the regulation of sperm functions such as capacitation, acrosome reaction, and sperm-oocyte fusion. However, oxidative stress (OS), caused by the imbalance between ROS and antioxidant scavenging systems of the male reproductive tract, can impair semen quality, leading to infertility. Spermatozoa are highly vulnerable to ROS, that are generated from both endogenous and exogenous sources. Pathological conditions, inducing supra-physiological levels of ROS, can damage sperm DNA and membrane, altering viability, motility and genomic integrity. Hence, many studies have been carried out to understand the impact of OS on spermatogenesis, during the past decades. Although, antioxidant oral administration has been demonstrated to enhance semen quality in subfertile men, it is still a matter of debate if it can positively influence fertilization and embryo developmental competence. This paper will review the physiological and the pathological roles of ROS, the sources of OS in vivo and in vitro, as well as the usefulness of antioxidants in male infertility and during sperm handling in ART.