Effect of exposure to CeO(2) nanoparticles on ram spermatozoa during storage at 4 °C for 96 hours

BACKGROUND: Cerium oxide nanoparticles (CeO(2) NPs) are able to store and release oxygen, conferring them scavenger activity against oxidative stress. However, their effects in reproductive systems are not yet well understood. The aim of the study was to investigate the effects of exposure of refrigerated ram semen to CeO(2) NPs for 96 h on the main structural and kinematic parameters of spermatozoa. METHODS: The ejaculates of 5 Sarda rams were collected, pooled and diluted in a soybean lecithin extender. Samples were exposed to increasing doses of CeO(2) NPs (0, 44 and 220 μg/mL) and stored at 4 °C for 96 h. Analyses of kinematic parameters (computer assisted sperm analysis, CASA), integrity of membranes (PI/PSA staining), ROS production (H(2)DCFDA staining) and DNA damage (sperm chromatin structure assay with acridine orange, SCSA) were performed every 24 h (0, 24, 48, 72 and 96 h of incubation). The experiment was carried out in 6 replicates. Data were analysed by repeated measures ANOVA with Bonferroni’s as post hoc test. When the assumption of normality was not met (ROS), non-parametric Kruskal-Wallis rank test was carried out. RESULTS: Exposure of ram spermatozoa to increasing doses of CeO(2) NPs had a beneficial effect on the main motility parameters from 48 h of incubation onward. Velocity of sperm cells was enhanced in the groups exposed to CeO(2) NPs compared to the control. Incubation with NPs had beneficial effects on the integrity of plasma membranes of spermatozoa, with higher percentage of damaged cells in the control group compared to the exposed ones. Production of ROS was not affected by exposure to NPs and its levels rose at 96 h of incubation. The integrity of DNA remained stable throughout the 96 h of storage regardless of co-incubation with NPs. CONCLUSIONS: We reported beneficial effects of CeO(2) NPs on kinematic and morphologic parameters of ram semen, such as motility and membrane integrity following 96 h of exposure. Furthermore, we also proved no genotoxic effects of CeO(2) NPs. These effects could not be related to an antioxidant activity of CeO(2) NPs, since ROS levels in exposed cells were similar to those of unexposed ones.