Immunocytochemical Localisation of Phospholipid Hydroperoxide Glutathione Peroxidase in Bull’s Spermatogenic Cells

Abstract

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is a selenoprotein, which protects biomembranes from oxidative damages, and it also accounts for almost the entire selenium content of mammalian testis. The present investigation was performed to localise PHGPx in the testis and in epididymal and ejaculated spermatozoa of the bull by using light and electron immunomicroscopy. The study also aimed to further clarify the possible functions of the protein in bull fertility. In the testis, spermatogenic cells of the adluminal tubular compartment showed cytoplasmatic immunostaining; whereas, in the epididymal and ejaculated spermatozoa immunostaining was specifically localised at the level of the head and mid-piece. Ultrastructural data revealed the presence of signals for PHGPx in different subcellular compartments of maturing and mature sperm (mitochondria, chromatin, nuclear envelope, acrosomes, cytoskeletal structures) suggesting that this enzyme plays versatile and important biological roles during spermatogenesis. The final localisation of the immunostaining at acrosomal level puts forward a new role of the protein which further emphasises its relevance in male reproduction: it is reported to anchor substrate of the sperm acrosome to the oocyte zona pellucida during the fertilisation process.

Role of Selenium and Selenoproteins in Male Reproductive Function: A Review of Past and Present Evidences

“…Similarly, immuno-signals were also observed in the epididymal and ejaculated sperm particularly in acrosome region. These dynamic strong signals at different stages of sperm maturation conform to the earlier biochemical observations indicating that GPX4 is essential for the optimal development and function of bovine sperm similar to other mammalian species [70].…”

“…In addition to these evidences, recently Parillo and colleagues [70] reported that strong expression signals of GPX4 protein were observed in seminiferous tubules (apical region) of healthy Chianina bulls, where it was localized in the cytoplasmic region of maturing sperm i.e., spermatogonia, round spermatids, and elongated spermatids. Similarly, immuno-signals were also observed in the epididymal and ejaculated sperm particularly in acrosome region.…”

Macro- and microelements in serum and seminal plasma as biomarkers for bull sperm cryotolerance

“…When Se concentrations are low during the final stages of spermatogenesis, GPX4 activity is decreased, leading to higher concentrations of active peroxides that can cause oxidative injury that can accumulate and lead to delayed viability impairment [ 33 ]. Moreover, Parillo et al [ 34 ] reported that strong expression signals of GPX4 protein were observed in the apical region of seminiferous tubules in bulls. These dynamic signals at different stages of sperm maturation suggest that GPX4 is essential for optimal bovine sperm development and function and that Se deficiency may lead to impaired spermatogenesis [ 34 ].…”

“…Moreover, Parillo et al [ 34 ] reported that strong expression signals of GPX4 protein were observed in the apical region of seminiferous tubules in bulls. These dynamic signals at different stages of sperm maturation suggest that GPX4 is essential for optimal bovine sperm development and function and that Se deficiency may lead to impaired spermatogenesis [ 34 ]. However, this last phase of spermatogenesis in bulls lasts 17 days; therefore, the concentration of microelements measured in the blood serum on the day of sperm collection could not truly be correlated with spermatogenesis itself.…”

“…Since all bulls were fed the same diet, we believe that the same observations would be found even if the blood serum had been collected before sperm collection; however, this assumption should be tested in a future study. The statistically significant difference in Se concentration in blood serum between bulls in the SAT and UNSAT groups in our study could also be explained by the strong expression of GPX4 in epididymal fluid, prostatic fluid and seminal vesicular fluid in fertile bulls [ 34 ].…”