Antioxidant effects of lycopene on bovine sperm survival and oxidative profile following cryopreservation

Reactive oxygen species overgeneration as a side effect of semen cryopreservation may lead to lipid peroxidation, protein degradation, DNA fragmentation and cell death, resulting in a decrease of sperm survival and fertilisation ability. Lycopene has been proposed as a potential supplement to semen extenders because of its antioxidant properties. The aim of this study was to evaluate the effects of lycopene on the structural integrity, functional activity and selected oxidative stress parameters of cryopreserved bovine sperm. Thirty bovine ejaculates were split into two aliquots and diluted with a commercial semen extender supplemented with 1.5 mmol/l lycopene or containing no supplement (control), cooled down to 4 °C, frozen and kept in liquid nitrogen. Prior to experiments, frozen straws were thawed at 37 °C for 20 s. Lycopene addition resulted in a higher sperm motility (P < 0.001), progressive motility (P < 0.001) and all secondary motion characteristics (P < 0.001 with respect to the average path velocity, linear velocity, velocity of curvilinear motion, beat cross frequency, path straightness and linearity; P < 0.01 in the case of the amplitude of lateral head displacement). Furthermore, lycopene exhibited protective effects on the sperm membrane (P < 0.05) and acrosomal (P < 0.01) integrity in comparison to control. An assay for metabolic function revealed that lycopene supplementation to the cryopreservation medium resulted in a higher preservation of the sperm mitochondrial activity (P < 0.001). Reactive oxygen species production as well as intracellular superoxide generation were decreased following lycopene addition (P < 0.01 in the case of reactive oxygen species; P < 0.001 with respect to superoxide production). Finally, the presence of lycopene led to a decrease in protein carbonyl production (P < 0.01), lipid peroxidation (P < 0.001) as well as oxidative DNA damage (P < 0.05) when compared to control. In conclusion, lycopene exhibited significant reactive oxygen species-trapping and antioxidant properties which may prevent oxidative damage to frozen-thawed sperm, and, thus, enhance the post-thaw vitality of male reproductive cells in cattle breeding.