IMPACT OF REACTIVE OXYGEN SPECIES ON SPERMATOZOA - A BALANCING ACT BETWEEN BENEFICIAL AND DETRIMENTAL EFFECTS

Reactive oxygen species (ROS) have beneficial or detrimental effects o n sperm functions depending on the nature and the concentration of the ROS involved, as well as the moment and the location of exposure, Exc essive generation of ROS in semen, mainly by neutrophils but also by a bnormal spermatozoa, could be a cause for infertility, Hydrogen peroxi de is the primary toxic ROS for human spermatozoa. Low concentrations of this ROS do not affect sperm viability but cause sperm immobilizati on mostly via depletion of intracellular ATP and the subsequent decrea se in the phosphorylation of axonemal proteins. High concentrations of hydrogen peroxide induce lipid peroxidation and result in cell death. On the other hand, the superoxide anion appears to play a major role in the development of hyperactivation and capacitation, The observatio ns that: (i) exogenously generated superoxide anions induce hyperactiv ation and capacitation; (ii) capacitating spermatozoa themselves produ ce elevated concentrations of superoxide anion over prolonged periods of time; and (iii) removal of this ROS by superoxide dismutase prevent s sperm hyperactivation and capacitation induced by various biological fluids, stress the importance of the superoxide anion in these proces ses.