Biological Relevance of Free Radicals in the Process of Physiological Capacitation and Cryocapacitation

Abstract

Before fertilization, spermatozoa must undergo a process called capacitation in order to fulfill their fertilization potential. This includes a series of structural, biochemical, and functional changes before a subsequent acrosome reaction and fusion with the oocyte. However, low temperatures during cryopreservation may induce a premature activation of capacitation-like changes, also known as cryocapacitation, immediately after thawing, which may lead to a decreased viability, motility, and fertilization ability of cryopreserved spermatozoa. Furthermore, cryopreservation is responsible for the overgeneration of reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, and hydroxyl radicals, which may result in the development of oxidative stress, cell membrane damage, and lipid peroxidation. Despite that, both capacitation and cryocapacitation are considered to be oxidative events; however, potential beneficial or detrimental effects of ROS depend on a wide array of circumstances. This review summarizes the available information on the role of free radicals in the process of capacitation and cryocapacitation of spermatozoa.

In Vitro versus Cryo-Induced Capacitation of Bovine Spermatozoa, Part 2: Changes in the Expression Patterns of Selected Transmembrane Channels and Protein Kinase A

“…Biochemical changes in the plasma membrane and other subcellular compartments have been linked to sperm capacitation [ 20 ]. Major molecular events associated with the capacitation process involve, among others, the activation of calcium channels with a subsequent alkalinization of the sperm cell, reactive oxygen species (ROS) generation (particularly superoxide and hydrogen peroxide) [ 8 , 21 ], cAMP synthesis and the activation of protein kinases, accompanied by cholesterol efflux from the sperm plasma membrane [ 22 ].…”

“…Capacitation-like changes or cryocapacitation may be described as an early relocation of phospholipids and cholesterol leaching from the plasma membrane, as well as premature consumption of energy generated by the mitochondrial respiratory chain directly after the thawing procedure, which may lead into the loss of sperm movement [ 6 , 7 , 8 ].…”

The Silent Threat to Women’s Fertility: Uncovering the Devastating Effects of Oxidative Stress

“…Meanwhile, chromosome abnormalities and problems with conception may arise if there is ROS-induced DNA damage, including double- and single-strand breaks and nucleotide alterations [ 35 ]. Lipid peroxidation, also potentially caused by OS, reduces fluidity and permeability of the oocyte membrane and, therefore, its ability to be fertilized [ 36 ]. OS can also cause protein oxidation, which may impede oocyte development and, therefore, fertility [ 37 ] ( Figure 1 ).…”

Diluent and Storage Time Effect on Sperm Abnormality and MDA Level in Muscovy Duck Semen at 27oC

“…Damage to the plasma membrane of spermatozoa causes abnormalities in the head and tail that affect locomotion and decrease the viability of semen so that it affects spermatozoa abnormalities. Spermatozoa head abnormalities are caused by the presence of free radicals that enter at the time of ejaculation (Benko et al, 2022). MDA has been widely used as an indicator of the presence of free radicals and the occurrence of oxidative damage, Cui et al (2018).…”