Cryoprotective effect of cysteine on cryopreservation associated protein tyrosine phosphorylation in buffalo spermatozoa

Abstract

In the present study the effect of cysteine, an antioxidant, on cryopreservation associated cryodamage in the buffalo
spermatozoa was studied. Ejaculated buffalo semen was divided into 2 aliquots. One aliquot was used to analyze fresh
semen quality parameters and the other aliquot was cryopreserved in tris based egg-yolk extender with or without
cysteine (5 mM) and sperm quality parameters like post-thaw motility, viability and membrane integrity were assessed.
All the sperm quality parameters were significantly improved upon the addition of cysteine. Interestingly the number of
tyrosine phosphorylated proteins detected was more (p32, p49, p55, p72, p86, p95 and p100) in cryopreserved sperm
than the fresh spermatozoa. However the degree of protein tyrosine phosphorylation with respect to p49, p55, p72, p86,
p95 and p100 proteins was significantly decreased in the cryopreserved spermatozoa supplemented with cysteine.
Hence cysteine acts as a potential antioxidant that reduces the protein tyrosine phosphorylation probably caused by
ROS induced signaling pathways by maintaining other sperm quality parameters. The addition of cysteine to the freezing
extender helps in minimizing the cryodamage associated with sperm cryopreservation.