Prostasomes as potential modulators of tyrosine phosphorylation in human spermatozoa

Prostasomes, vesicles present in human semen, are known to play a role in male fertility. However, the mechanisms involved are still poorly understood. The present study looks at the direct influence of different concentrations of prostasomes on human sperm function in conditions supporting capacitation in vitro. Five million Percoll selected spermatozoa were incubated for 3 h at 37°C under an atmosphere of 5% CO₂ in air, in 100 µl Biggers Whitten Whittingham's medium (BWW) containing polyvinyl alcohol (PVA, 1 mg/ml) and bovine serum albumin (BSA; 3 mg/ml) in the absence or presence of increasing concentrations of prostasomes (expressed in terms of their cholesterol content: 15; 30; 45 nmoles per 100 µL of incubation medium). After in vitro exposure of spermatozoa to prostasomes, our data indicate that i) tyrosine phosphorylation intensity of the 107 KDa protein band was dose dependently lower and ii) the percentage of viable and progressive motile spermatozoa was unchanged and the percentage of non-progressive motility decreased. In addition, the incubation of prostasomes with spermatozoa resulted in an enrichment of their lipid content. Our experiments suggest that adhesion of prostasomes to spermatozoa could be responsible for the decrease in Tyrosine phosphorylation and the alteration of the mean curvilinear velocity (VCL) and the average path velocity (VAP).