Cell Biology Symposium
Redox regulation is being unveiled as a major mechanism regulating sperm functionality, probably at the same level as tyrosine phosphorylation. Sophisticated mechanisms must be present to maintain redox status under physiological control. The spermatozoa has antioxidant defenses, including glutathione, and other enzymatic antioxidant defenses such as thioredoxin and peroxiredoxin families of proteins. Oxidative stress is thus better defined as the fail in the regulation of redox signalling due either overproduction of ROS, or exhaustion of regulatory mechanisms. The stallion spermatozoa is a paradigm of this; recent research has shown apparently paradoxical results, in this regard more fertile spermatozoa show increased ROS production.A major component of the alteration of ROS homeostasis in cryopreserved spermatozoa is the exhaustion of intrinsic antioxidant defence mechanisms. Thiols and particularly glutathione (GSH) are essential for the regulation of stallion sperm functionality. As cysteine is a pre cursor of GSH, we hypothesized that stallion spermatozoa are able to synthesize this tri-peptide using exogenous cysteine. We investigated the presence of two enzymes required to synthesize GSH (GSS and GCLC); using western blotting and immunocytochemistry we detected both enzymes in stallion spermatozoa. The inhibition of glutamate cysteine ligase reduced the recovery of GSH by addition of cysteine after depletion, suggesting that stallion spermatozoa may use exogenous cysteine to regulate GSH. Mean concentration of GSH in stallion spermatozoa was 8.2±2.1 mM /109spermatozoa, well above the nanomolar ranges reported for other mammals. In addition we have reported the presence of the soluble carrier family 7 member 11 (SLC7A11) antiporter, which exchanges extracellular cystine (Cyss) for intracellular glutamate.
The investigations of the author have been funded by Ministerio de Ciencia y Competividad- FEDER AGL 2017-83149-R and Junta de Extremadura FEDER IB16030 and GR18008