Akt (protein kinase B) preserves motility in stallion sperm by inhibiting caspases 3 and 7

Abstract

s / Journal of Equine Veterinary Science 34 (2014) 67 67 incubation, the Akt inhibitor induced, at 30mM, a significant decrease in the percentage of total motile spermatozoa (30% vs. 50% in controls), linearly motile sperm (6% vs. 18% in controls), circular (39.5 vs. 63.5 mm/s in controls), average (21.5 vs. 36.7 mm/s in controls) and straight line velocities (12.5 vs. 21mm/s in controls) (p<0.05). After two hours of incubation at 37 C, the inhibitor significantly reduced circular velocity and average velocity (p<0.05). The data suggest that Akt plays a role in the regulation of stallion sperm motility and velocities. After 4 and 6 h of incubation all parameters of spermmotility and kinematics were reduced (p<0.01), independent of treatment. Likewise, Akt inactivation reduced membrane integrity leading to enhanced membrane permeability. Inhibition of Akt phosphorylation affected, in a dose and time dependent manner, mitochondrial membrane potential of stallion spermatozoa. After one hour of incubation, 30mM of Akt inhibitor significantly reduced mitochondrial membrane potential, based upon both JC-1 and mitotracker deep red assays. After two hours of incubation, 20 and 30mM of Akt inhibitor decreased mitochondrial membrane potential when determined with mitotracker deep red but not with JC-1. For the latter, mitochondrial membrane potential was only significantly decreased at 30mM. After one hour of incubation, all inhibitor concentrations tested reduced the percentage of caspase-negative, live spermatozoa in a positive dose-dependent manner (p<0.01). The percentage of caspase 3 positive spermatozoa also increased in a dose dependent manner, this effect being especially evident after four hours of incubation at 37 C. On the other hand, neither the percentage of spermatozoa suffering oxidative stress, the production of mitochondrial superoxide radical, DNA oxidation or sperm DNA fragmentation changed when Akt was inhibited.