Sperm Redox System Equilibrium: Implications for Fertilization and Male Fertility

Structural and regulatory requirements of mammalian spermatozoa in both development and function make them extremely unique cells. Looking at the complexity of spermatozoon structure and its requirements for both motility and quick breakdown within the post-fertilization environment, as well as its functional needs as an extremely streamlined cell with high energy requirements, demonstrate the high importance of oxidative-reductive processes. The oxidative state of the testis and epididymis during sperm development and maturation highly influences sperm structure, with a high dependence on disulfide bond formation, facilitated by thiol mediated processes. However, once functionally active, sperm transition to a new high-risk functional paradigm requiring low levels of reactive oxygen species (ROS) while also being highly susceptible to oxidative damage due to the high proportion of polyunsaturated fatty acids within the lipid bilayer of the plasmalemma and the lack of cytosolic antioxidant defenses. This chapter highlights how glutathione and thioredoxin systems mediate the oxidative environment of the male reproductive tract and facilitate the successful development, maturation and function of mammalian spermatozoa.