The importance of bovine seminal plasma proteins in the sperm function and fertility

Bovine livestock is one of the most important economic and social sectors for many countries. In this sense, the development of strategies to improve reproductive bull fertility and reproduction rates is relevant. It's highlighted the role of seminal plasma proteins (SPP) in reproductive fertility, so it has found close relationships among studies on the structure and biological activity of SPP, with seminal quality, including viability, sperm motility, and morphology. In addition, they have been found to regulate sperm functions such as capacitation, acrosome reaction, and they are even related to protecting sperm against thermal and oxidative stress. Moreover, the methods of separation and protein identification and their contribution to characterizing the bovine SP proteome should be also highlighted. In this sense, the most recent studies have been directed towards developing supplements with SPP that improve quality sperm subjected to cryopreservation processes. Research has begun and should forward to establish how the networks or sets of proteins are related to the functioning and fertility of sperm, the search for biomarkers of fertility, and the use of proteins in biotechnological processes, to increase efficiency reproductive.

Novaluron Has Detrimental Effects on Sperm Functions

Although novaluron is an insect growth regulator with a low mammalian acute toxicity and a low risk to the environment and nontarget organisms, toxic effects of novaluron have been reported. However, no studies have yet evaluated the effect of novaluron on reproduction. Therefore, we examined the effects of novaluron on sperm functions. The spermatozoa of ICR mice were incubated with various concentrations of novaluron to induce capacitation. Then, sperm motion parameters and capacitation status were evaluated using CASA program and H33258/chlortetracycline staining. In addition, PKA activity and tyrosine phosphorylation were evaluated by Western blotting. After exposure, various sperm motion parameters were significantly decreased in a dose-dependent manner. The acrosome reaction was also significantly decreased in the high concentration groups. Sperm viability was significantly reduced at the highest concentration. In addition, PKA activity and tyrosine phosphorylation were also significantly altered. Thus, novaluron affects sperm viability, sperm motility, and motion kinematics during capacitation. Furthermore, it may promote the reduction in acrosome reactions. The physiological suppression of sperm function may depend on abnormal tyrosine phosphorylation via the alteration of PKA activity. Therefore, we suggest that it is necessary to consider reproductive toxicity when using novaluron as a pesticide.

N-Methyl-d-aspartic Acid (NMDA) Receptor Is Involved in the Inhibitory Effect of Ketamine on Human Sperm Functions

Ketamine, which used to be widely applied in human and animal medicine as a dissociative anesthetic, has become a popular recreational drug because of its hallucinogenic effect. Our previous study preliminarily proved that ketamine could inhibit human sperm function by affecting intracellular calcium concentration ([Ca2+]i). However, the specific signaling pathway of [Ca2+]i induced by ketamine in human sperm is still not clear yet. Here, the N-methyl-d-aspartic acid (NMDA) receptor was detected in the tail region of human sperm. Its physiological ligand, NMDA (50 μM), could reverse ketamine’s inhibitory effect on human sperm function, and its antagonist, MK801 (100 μM), could restrain the effect of NMDA. The inhibitory effect caused by 4 mM ketamine or 100 μM MK801 on [Ca2+]i, which is a central factor in the regulation of human sperm function, could also be recovered by 50 μM NMDA. The results suggest that the NMDA receptor is probably involved in the inhibitory effect of ketamine on human sperm functions.

Bovine Follicular Fluid Derived Extracellular Vesicles Modulate the Viability, Capacitation and Acrosome Reaction of Bull Spermatozoa

While follicular fluid (FF) is known to enhance the functional properties of spermatozoa, the role of FF-derived extracellular vesicles (EVs) in this respect is unknown. We hypothesized that bovine FF EVs convey signals to spermatozoa supporting sperm viability, inducing sperm capacitation and acrosome reaction. In this study, the effects of bovine FF EVs on sperm functions are evaluated. Irrespective of the size of the follicles which FF EVs had originated from, they were capable of supporting sperm viability, inducing capacitation and acrosome reaction. These effects were specific to the source of bovine FF EVs, as human-cell-line-derived or porcine FF EVs did not affect spermatozoa viability or induced capacitation and acrosome reaction. A minimum of 5 × 105 EVs/mL was adequate to maintain sperm viability and induce capacitation and acrosome reaction in spermatozoa. Interestingly, with FF EV trypsin treatment, FF EVs lost their ability to support sperm functions. In conclusion, this study demonstrates that bovine FF EVs can support spermatozoa function and may contribute to a favorable periconceptional microenvironment. This is an important aspect of the interactions between different sexes at the earliest stages of reproduction and helps to understand molecular mechanisms modulating processes such as sperm competition and female cryptic choice.

Activation of PTH1R alleviates epididymitis and orchitis through Gq and β-arrestin-1 pathways

Inflammation in the epididymis and testis contributes significantly to male infertility. Alternative therapeutic avenues treating epididymitis and orchitis are expected since current therapies using antibiotics have limitations associated to side effects and are commonly ineffective for inflammation due to nonbacterial causes. Here, we demonstrated that type 1 parathyroid hormone receptor (PTH1R) and its endogenous agonists, parathyroid hormone (PTH) and PTH-related protein (PTHrP), were mainly expressed in the Leydig cells of testis as well as epididymal epithelial cells. Screening the secretin family G protein–coupled receptor identified that PTH1R in the epididymis and testis was down-regulated in mumps virus (MuV)- or lipopolysaccharide (LPS)-induced inflammation. Remarkably, activation of PTH1R by abaloparatide (ABL), a Food and Drug Administration–approved treatment for postmenopausal osteoporosis, alleviated MuV- or LPS-induced inflammatory responses in both testis and epididymis and significantly improved sperm functions in both mouse model and human samples. The anti-inflammatory effects of ABL were shown to be regulated mainly through the Gq and β-arrestin-1 pathway downstream of PTH1R as supported by the application of ABL in Gnaq± and Arrb1−/− mouse models. Taken together, our results identified an important immunoregulatory role for PTH1R signaling in the epididymis and testis. Targeting to PTH1R might have a therapeutic effect for the treatment of epididymitis and orchitis or other inflammatory disease in the male reproductive system.

Quantitative phosphoproteomics reveals GSK3A substrate network is involved in the cryodamage of sperm motility

During sperm cryopreservation, the most significant phenotype of cryodamage is the decrease of sperm motility. Several proteomic studies have already been performed to search for key regulators at the protein level. However, sperm functions are known to be highly regulated by phosphorylation signaling. Here, we constructed a quantitative phosphoproteome to investigate the expression change of phosphorylated sites during sperm cryopreservation. A total of 3167 phosphorylated sites are identified and 848 of them are found to be significantly differentially expressed. Bioinformatics analysis showed that the corresponding genes of these regulated sites are highly associated with sperm motility, providing a connection between the molecular basis and the phenotype of cryodamage. We then performed kinase enrichment analysis and successfully identified GSK3A as the key kinase that may play an important role in the regulation of sperm motility. We further constructed a GSK3A centric network that could help us better understand the molecular mechanism of cryodamage in sperm motility. Finally, we also verified that GSK3A was abnormally activated during this process. The presented phosphoproteome and functional associations provide abundant research resources for us to learn the regulation of sperm functions, as well as to optimize the cryoprotectant for sperm cryopreservation.

Soluble adenylyl cyclase inhibition prevents human sperm functions essential for fertilization

Soluble adenylyl cyclase (sAC: ADCY10) has been genetically confirmed to be essential for male fertility in mice and humans. In mice, ex vivo studies of dormant, caudal epididymal sperm demonstrated that sAC is required for initiating capacitation and activating motility. We now use an improved sAC inhibitor, TDI-10229, for a comprehensive analysis of sAC function in mouse and human sperm. In contrast to caudal epididymal mouse sperm, human sperm are collected post-ejaculation, after sAC activity has already been stimulated. In addition to preventing the capacitation-induced stimulation of sAC and protein kinase A activities, tyrosine phosphorylation, alkalinization, beat frequency, and acrosome reaction in dormant mouse sperm, sAC inhibitors interrupt each of these capacitation-induced changes in ejaculated human sperm. Furthermore, we show for the first time that sAC is required during acrosomal exocytosis in mouse and human sperm. These data define sAC inhibitors as candidates for non-hormonal, on-demand contraceptives suitable for delivery via intravaginal devices in women.