Effects of reactive oxygen species action on sperm function in spermatozoa

Authors: Guthrie, Howard; Welch, Glenn

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2012
Publication Date: 11/20/2012
Citation: Guthrie, H.D., Welch, G.R. 2012. Effects of reactive oxygen species action on sperm function in spermatozoa. Theriogenology. 78(8):1700-1708.

Interpretive Summary: Semen storage (fresh or frozen) for breeding of farm animals and poultry is required for obtaining the most efficient use of the semen by artificial insemination. One of the major problems of non-frozen or frozen storage in many species is the degradation of molecules in the membrane of the sperm cells by naturally occurring reactive molecules containing oxygen which result in cell damage. The purpose of this review was to describe the extent of the problem in sperm of swine and other species, and highlight ways to prevent this problem. First we developed new assays to measure formation of reactive molecules containing oxygen and membrane damage. We found that swine sperm are very resistant to formation reactive molecules containing oxygen and ensuing cell damage. However, the literature indicates that the sperm of bovine, poultry, and human sperm are highly susceptible to damage by reactive molecules containing oxygen. So our new assays will be very useful for researchers studies of semen preservation in other species.

Technical Abstract: Reactive oxygen species (ROS) formation and lipid peroxidation have been recognized as problems for sperm survival and fertility. The precise roles and detection of superoxide (SO), hydrogen peroxide (HP), and membrane lipid peroxidation have been problematic because of the low specificity and sensitivity of the established chemiluminescence assay technologies. We developed flow cytometric assays to measure SO, HP, membrane lipid peroxidation, and inner mitochondrial transmembrane potential (''m) in boar sperm. These methodologies were sufficiently sensitive to permit detection of early changes in ROS formation in sperm cells that were still viable. Basal ROS formation and membrane lipid peroxidation in the absence of ROS generators were low in viable sperm of both fresh and frozen-thawed boar semen, affecting < 4% of the sperm cells on average. However, this not the case in other species because human, bovine, and poultry sperm exhibit large increases in sperm ROS formation, lipid peroxidation, loss of motility, and death in vitro. Closer study of the effects of ROS formation on the relationship between sperm motility and ATP content in boar sperm was conducted using menadione (mitochondrial SO generator) and HP treatment. Menadione or HP caused an immediate disruption of motility with delayed or no decrease in sperm ATP content, respectively. Overall, the inhibitory affects of ROS on motility point to a mitochondrial independent mechanism. The reduction in motility may have been due to a ROS induced lesion in ATP utilization or in the contractile apparatus of the flagellum.