Sperm Na+, K+-ATPase α4 and plasma membrane Ca2+-ATPase (PMCA) 4 regulation in asthenozoospermia.

Asthenozoospermia, which is characterized by reduced motility, is one of the etiologies of male infertility. Its biochemical and functional consequences include altered ATPase activity. This study investigated the activities of Na+, K+-ATPase and Ca2+-ATPase and the expression of Na+, K+-ATPase α4 and PMCA4 isoforms in human sperm of asthenozoospermic infertile men. Nineteen samples from asthenozoospermic infertile couples were examined in this study. Computerized-assisted semen analysis (CASA) was performed, and the enzyme activity was measured based on the ability of ATPase to release organic phosphate from ATP as a substrate. The Na+, K+-ATPase α4 and PMCA4 isoform expression levels were measured by western immunoblotting, whereas the protein distribution was examined by immunocytochemistry. This showed that the Na+, K+-ATPase activity and the Na+, K+-ATPase α4 isoform expression were lower in the asthenozoospermia group than in the normozoospermia group (8.688±1.161 versus 13.851±1.884 µmol Pi/mg protein/h, respectively; p>0.05). In contrast, the Ca2+-ATPase activity was significantly higher in the asthenozoospermia group than in the normozoospermia group (11.154±1.186 versus 2.725±0.545 µmol Pi/mg protein/h, respectively; p<0.05). In comparison, PMCA4 expression in the asthenozoospermia group was lower than in the normozoospermia group (p>0.05). The altered ATPase activity and isoform expression in asthenozoospermia may impair sperm structure and function.

Sperm-associated antigen 11A is expressed exclusively in the principal cells of the mouse caput epididymis in an androgen-dependent manner.

BACKGROUND: Epididymal sperm maturation occurs via interactions between sperm and proteins secreted by the epididymal epithelium. Although this is an important process, the genes that encode the involved proteins remain largely uncharacterized. Previous studies have demonstrated that the genes involved in sperm maturation are regulated by androgen. Spag11a is an epididymal gene that is influenced by androgen. However, little is known about the putative role of this gene in the sperm maturation process. The objective of this study was to characterize Spag11a in the mouse epididymis. METHODS: In silico analyses were performed to predict signal peptides and functional domains. Spag11a expression was measured by quantitative real-time RT-PCR. Western blots and immunocytochemistry were performed to determine protein expression. RESULTS: SPAG11A is a member of the beta defensin protein family and constitutes a secretory protein. Spag11a was expressed exclusively in the epididymis. Moreover, it exhibited region-specific expression in the caput, which is typical for genes that are involved in creating a suitable microenvironment for sperm maturation. Mouse Spag11a was regulated by androgen. A significant decrease of Spag11a expression was observed at third day following a gonadectomy (P < 0.001). Interestingly, testosterone replacement therapy was able to maintain the expression almost at the normal level, indicating a dependency on androgen. Besides androgen, testicular factors influenced Spag11a expression in a different way. This was revealed by efferent duct ligation in which Spag11a was transiently up-regulated at the third day following the ligation before returning to the normal level at day 5. Spag11a regional expression was also observed at protein level detected by western immunoblotting which revealed a clear band in the caput but not in other regions. The prediction that SPAG11A is a secretory protein was confirmed by immunocytochemical analyses indicating cell-specific expression mainly in the caput principal cells and detection of the protein in epididymal luminal fluid and spermatozoa. CONCLUSIONS: Based on the characteristics of Spag11a, it is likely that this gene has a specific role in epididymal sperm maturation. Further studies using functional assays are necessary to confirm this finding.