Caspase activation, hydrogen peroxide production and Akt dephosphorylation occur during stallion sperm senescence.

The study focuses on examining the processes that lead to sperm cell death after ejaculation, particularly in stallions. Key findings indicate that this cell death potentially unfolds through an apoptosis-like phenomenon, influenced by internal production of hydrogen peroxide and a lack of factors preserving Akt in a phosphorylated state.

Objective and Methodology

• The objective of this study was to reveal the mechanisms that cause sperm death after ejaculation. The object of the study was stallion ejaculates. The primary tools used for the experiments were incubation in BWW media and evaluation via flow cytometry and CASA (Computer-Assisted Sperm Analysis).
• Ejaculates were incubated in BWW media for 6 hours at a constant temperature of 37°C. During this incubation period, researchers frequently assessed sperm attributes such as motility and kinematics by using CASA. They also determined the mitochondrial membrane potential and the integrity and permeability of the sperm membrane.
• Along with these assessments, the team detected active caspase 3, hydrogen peroxide, superoxide anion and Akt phosphorylation, at various intervals during the incubation period.

Key Findings

• Findings revealed that substantial degradation of sperm functionality happens after 6 hours of incubation, with marked reductions in the proportion of motile and progressively motile sperm detected after just 1 hour of the 6-hour incubation period.
• Notably, the deterioration in sperm functionality after 6 hours was associated with a significant surge in hydrogen peroxide production and a surge in caspase 3 activity.
• Another key observation was that the percentage of phosphorylated Akt reached its lowest point after the 6-hour incubation period, suggesting a correlation between the decrease in Akt phosphorylation and the sperm functionality degradation.

Implications and Conclusions

• The study suggests that sperm death during in vitro incubation is primarily an apoptosis-like event. Behind this cell death is an endogenous production of hydrogen peroxide and an absence of pro-survival factors that would otherwise maintain the phosphorylation of Akt.
• The insights gleaned from this research could provide a foundation for new strategies regarding stallion sperm conservation. By understanding the molecular mechanisms that drive sperm death, scientists could better strategize how to combat it and enhance sperm longevity and viability.