The antioxidant glutathione peroxidase family and spermatozoa: a complex story.

Oxidative damage is one threat spermatozoa have to face during epididymal maturation and storage. However, it is clear that reactive oxygen species (ROS) are also central for sperm physiology in processes such as sperm maturation and capacitation. It is therefore essential that there exists around sperm cells a fine balance between ROS production and recycling. To do so, sperm cells and epididymal epithelial cells rely on common enzymatic ROS scavengers such as superoxide dismutase (SOD), glutathione peroxidases (GPX) and catalase (CAT) as well as more specific types such as indoleamine dioxygenase (IDO). Among the catalytic triad (SOD/GPX/CAT), the glutathione peroxidase protein family occupies a peculiar position, since several GPX have been found to be present on and around epididymal transiting sperm cells. Here, we will review our present knowledge regarding GPX expression, presence and putative role(s) within the epididymis and on spermatozoa. Taking into account our recent findings regarding the epididymal expression of indoleamine dioxygenase in mouse we will also discuss how we think this superoxide anion recycling enzyme completes the complex ROS generation/recycling balance in this organ.