Impacts of Oxidative Stress and Antioxidants on Semen Functions
Gametes are susceptible to reactive oxygen species (ROS) attack. When manipulated in vitro during assisted reproductive techniques, these cells run the risk of generating and being exposed to supra-physiological level of ROS . Defective sperm functions are the most prevalent causes of male infertility and a difficult condition to treat . Many environmental, physiological, and genetic factors have been implicated in the poor sperm functions and infertility [3–6]. Thus, it is very important to identify the factors/conditions which affect normal sperm functions. Among various causes, oxidative stress (OS) has been attributed to affect the fertility status and physiology of spermatozoa . The term oxidative stress is generally applied when oxidants outnumber antioxidants . The imbalance between the production of reactive oxygen species (ROS) and a biological systems ability to readily detoxify the reactive intermediates or easily repair the resulting damage is known as oxidative stress . The main destructive aspects of oxidative stress are the production of ROS, which include free radicals and peroxides . The production of ROS by sperm is a normal physiological process, but an imbalance between ROS generation and scavenging activity is detrimental to the sperm and associated with male infertility . Physiological levels of ROS influence and mediate the gametes [11–13] and crucial reproductive processes, such as sperm-oocyte interactions , implantation and early embryo development . Against ROS attack, sperm cells are well equipped with a powerful defense system of antioxidants . Antioxidants are the main defense factors against oxidative stress induced by free radicals . This article reviews the impact of oxidative stress and reactive oxygen species (ROS) on spermatozoal functions, causes of ROS generation, and antioxidative strategies to reduce the oxidative stress. In addition, the significance of antioxidants in reproduction and oxidative stress as a contraceptive measure will be reviewed.