Reactive Oxygen Species (ROS) and Male Fertility

Abstract

Oxidative energy production is inevitably associated with the generation of reactive oxygen species ROS , excessive concentrations of which can lead to cellular pathology. " free radical may be defined as any molecule that has one or more unpaired electrons. The superoxide anion, the hydroxyl radical, and the hypochlorite radical vulnerable to oxidative stress as the sperm membrane is rich in unsaturated fatty acids and lacks the capacity for DN" repair. Spermatozoa are particularly susceptible to ROS-induced damage because their plasma membranes contain large quantities of polyunsaturated fatty acids PUF" and their cytoplasm contains low concentrations of the scavenging enzymes. Many clinical and research institutes are investigating the usefulness of antioxidant supplementation and their role in prevention of the infertility problems. Incubation under oxygen in vitro was detrimental to human spermatozoa, decreasing motility and viability. Since then, many reports have associated ROS with impaired sperm function, including decreased motility, abnormal morphology, and decreased sperm-egg penetration. Increasing knowledge of the mechanisms whereby ROS and endogenous antioxidant systems influence reproductive processes can assist to optimize the application of exogenous antioxidants to fertility treatment.

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“…High concentrations of ROS overwhelm the endogenous antioxidant defenses of gametes, causing multiple derangements. High concentrations of ROS cause peroxidative damage to plasma membrane PUFA, DNA damage, the depletion of mitochondrial adenosine triphosphate (ATP), apoptosis and the loss of sperm motility (4,5,10).…”

“…At low concentrations, ROS act as second messengers that regulate increases in cyclic adenosine monophosphate (cAMP), the activation of protein kinase A (PKA), the phosphorylation of PKA substrates of the arginine-X-X-(serine/threonine) motif, the phosphorylation of extracellular signal-regulated kinase (ERK) and mitogenactivated protein kinase (MEK) proteins and the threonineglutamate tyrosine motif, as well as fibrous sheath protein tyrosine phosphorylation (4,5,10). These functions are involved in sperm capacitation, acrosome reaction and oocyte fertilization (4,5,10).…”

“…These functions are involved in sperm capacitation, acrosome reaction and oocyte fertilization (4,5,10).…”

“…Sperm plasma membranes contain large quantities of polyunsaturated fatty acids (PUFA) whereas their cytoplasm contains low concentrations of enzymes that scavenge ROS (4,5,10). High concentrations of ROS overwhelm the endogenous antioxidant defenses of gametes, causing multiple derangements.…”

“…Reactive oxygen species (ROS) are toxic to both spermatozoa and oocytes, with the former being more sensitive to high ROS concentrations (3)(4)(5)(6)(7)(8)(9)(10). MacLeod demonstrated that oxidative stress was responsible for decreases in sperm motility and that the adverse effects of increased oxygen concentrations could be mitigated by adding catalase to cultures (5).…”