Functional significance of mouse seminal vesicle sulfhydryl oxidase on sperm capacitationin vitro

Abstract

During ejaculation, cauda epididymal spermatozoa are suspended in a protein-rich solution of seminal plasma which is composed of proteins mostly secreted from the seminal vesicle. These seminal proteins interact with the sperm cells and bring about changes in their physiology, so that they can become capacitated in order for the fertilization to take place. Sulfhydryl oxidase (SOX) is a member of the QSOX family and its expression is found to be high in the seminal vesicle secretion of mouse. Previously, it has been reported to cross-link thiol containing amino acids among major seminal vesicle secretion (SVS) proteins. However, its role in male reproduction is unclear. In this study, we determined the role of SOX on epididymal sperm maturation and also disclosed the binding effect of SOX on the sperm fertilizing ability in vitro. In order to achieve the above two objectives, we constructed a Sox clone (1.7 kb) using a pET-30a vector. His-tagged recombinant Sox was over expressed in Shuffle Escherichia coli cells and purified using His-Trap column affinity chromatography along with hydrophobic interaction chromatography. The purified SOX was confirmed by Western blot analysis and by its activity with DTT as a substrate. Results obtained from immunocytochemical staining clearly indicated that SOX possesses a binding site on the sperm acrosome. The influence of SOX on oxidation of sperm sulfhydryl to disulfides during epididymal sperm maturation was evaluated by a thiol labelling agent, mBBr. The SOX protein binds on to the sperm cells and increases their progressive motility. The effect of SOX binding on reducing the [Ca2+]i concentration in sperm head, was determined using a calcium probe, Fluo-3 AM. The inhibitory influence of SOX on sperm acrosome reaction was shown by using calcium ionophore A32187 to induce the acrosome reaction. The acrosome-reacted sperm were examined by staining with FITC-conjugated Arachis hypogaea (peanut) lectin. Furthermore, immunocytochemical analysis revealed that SOX remains bound to the sperm cells in the uterus but disappears in the oviduct during their transit in the female reproductive tract. The results from the above experiment revealed that SOX binding on to the sperm acrosome prevents sperm capacitation by affecting the [Ca2+]i concentration in the sperm head and the ionophore-induced acrosome reaction. Thus, the binding of SOX on to the sperm acrosome may possibly serve as a decapacitation factor in the uterus to prevent premature capacitation and acrosome reaction, thus preserving their fertilizing ability.

Cytoprotective effects of Nigella sativa seeds on monosodium glutamate induced seminal vesicle damages: Histological and immunohistochemical studies

“…The viscous, gel-like nature of the vesicular glands secretion and formation of copulatory plug at the time of mating are products of complex biochemical interaction that involves the coagulation of a specific protein produced by the seminal vesicles (Adebayo et al, 2014). These seminal proteins interact with the sperms leading to changes in their physiology to facilitate capacitation for the fertilization to occur (Aumüller and Riva, 1992;Clavert et al, 1990;Balu et al, 2022). In addition to secretion of the seminal fluid, epithelial cells of seminal gland are capable of reabsorption of fluids or dissolved substances, performing spermatophagy (ingestion and degradation of damaged spermatozoa), modification of sperm functions (motility, capacitation), and immunosuppression within the female genital system (Aumüller and Riva, 1992).…”

“…Much of the biological activity of the NSS had been shown to be due to its active ingredient; thymoquinone (Ahmad et al, 2013) Seminal vesicle plays an important role in male fertility. Its secretion is essential for semen coagulation, sperm motility, sperm capacitation, stability of sperm chromatin and suppression of the immune response in the female reproductive tract ( Pang et al, 1979;Peitz and Olds-Clarke, 1986;Clavert et al, 1990;Gonzales, 2001;Balu et al, 2022). Seminal vesicle was reported to be sensitive to MSG which may lead to impairment to its functions (Iamsaard et al, 2014) that might be cause male infertility especially in long term use.…”