Free radicals in reproductive processes

Reactive oxygen and nitrogen species (ROS/RNS) play an essential part in biological processes. Significant amounts of ROS and RNS cause a decrease in the activity of endogenous antioxidant systems. Mitochondrial electron transport chains, viral and bacterial infections, industrial pollutants, and various cellular pathways represent basic sources of ROS production. Moderate concentrations of ROS and RNS have a beneficial effect on reproductive processes such as sperm maturation, capacitation, acrosomal reaction and fertilization. Excessive ROS production impairs sperm function and leads to DNA damage, sperm fusion and infertility. ROS can cause infertility through two mechanisms: damage to sperm membranes with a subsequent decrease in their motility and damage to sperm DNA. Increased radical formation under conditions of development of oxidative stress provokes the formation of numerous «holes» in sperm membranes, rich in polyunsaturated fatty acids. The entry of Na+ and Ca2+ ions through the formed «holes» causes a change in osmolality, the formation of soluble calcium phosphates and activation of proteolytic and phosphoglycolytic enzymes through Ca2+. Regulating the balance of pro- and antioxidant systems will ensure the normal course of reproductive processes. The main way of such regulation is to reduce (or eliminate) the risks of adverse endogenous and exogenous effects against the background of dosed consumption of fat- and water-soluble antioxidants.