Oxidation and the spermatozoa.

The unusually high content of phospholipid-bound polyunsaturated fatty acids (PUFA) in the sperm plasma membrane drew attention to their potential physiological significance. Docosahexaenoic acid (22:6) is quantitatively the most important fatty acid. The high PUFA content of sperm membranes makes them vulnerable to peroxidative changes, since PUFA containing two or more double bonds are readily attacked by oxygen radicals. The effects of oxidation on sperm function have been suggested as detrimental as well as beneficial. Generation of reactive oxygen species (ROS) and peroxidation of sperm membrane can bring negative effects on motility, midpiece abnormalities, and sperm-oocyte fusion. ROS trigger sperm hyperactivation, and may support the capacitation of spermatozoa and fertilization. Spermatozoa are protected by various antioxidants and antioxidant enzymes in the seminal plasma or in spermatozoa itself. When the gametes are cultured in vitro, they become more susceptible to oxidative damage. Addition of antioxidants in the media brought beneficial effects in preventing loss of motility and inhibiting lipid peroxidation. Treating patients with antioxidants has shown to have a positive effect on improving fertilization in limited data. The mechanism of antioxidant effects on spermatozoa needs to be further studied.