Protein kinase C activity in boar sperm

The compound YK 3-237 promotes pig sperm capacitation-related events

Before fertilization of the oocyte, the spermatozoa must undergo through a series of biochemical changes in the female reproductive tract named sperm capacitation. Spermatozoa regulates its functions by post-translational modifications, being historically the most studied protein phosphorylation. In addition to phosphorylation, recently, protein acetylation has been described as an important molecular mechanism with regulatory roles in several reproductive processes. However, its role on the mammal's sperm capacitation process remains unraveled. Sirtuins are a deacetylase protein family with 7 members that regulate protein acetylation. Here, we investigated the possible role of SIRT1 on pig sperm capacitation-related events by using YK 3-237, a commercial SIRT1 activator drug. SIRT1 is localized in the midpiece of pig spermatozoa. Protein tyrosine phosphorylation (focused at p32) is an event associated to pig sperm capacitation that increases when spermatozoa are in vitro capacitated in presence of YK 3-237. Eventually, YK 3-237 induces acrosome reaction in capacitated spermatozoa: YK 3-237 treatment tripled (3.40 ± 0.40 fold increase) the percentage of acrosome-reacted spermatozoa compared to the control. In addition, YK 3-237 induces sperm intracellular pH alkalinization and raises the intracellular calcium levels through a CatSper independent mechanism. YK 3-237 was not able to bypass sAC inhibition by LRE1. In summary, YK 3-237 promotes pig sperm capacitation by a mechanism upstream of sAC activation and independent of CatSper calcium channel.

Sperm traits and seminal plasma proteome of locally adapted hairy rams subjected to intermittent scrotal insulation

The present study evaluated the effects of heat stress on reproductive parameters of hairy rams. Six animals were subjected to scrotal insulation during four consecutive nights (6 PM - 6 AM). Day (D) 0 was the first day of insulation. Scrotal circumference increased from 30.5 ± 0.3 cm (at pre-insulation) to 31.8 ± 0.4 cm on D4, decreased 3.9 cm on D28, returning to 30.6 ± 0.6 cm on D57. Sperm concentration decreased from 3.7 ± 0.12 ×109 sperm/mL before insulation to 2.6 ± 0.1 ×109 on D23, returning to normal on D57. Sperm motility averaged 75 ± 2.9% before insulation, was undetectable on D23, and became normal on D77. Sperm with normal morphology reached 5.9 ± 2.6% on D35 but recovered (86.8 ± 2.1%) on D91. Sperm DNA integrity decreased from 86.5 ± 4.7% before insulation to 11.1 ± 3.7% on D63, returning to pre-insulation values on D120. Sperm BSP immunostaining was reduced after scrotal insulation. Variations in seminal protein abundances coincided with changes in sperm parameters. Seminal plasma superoxide dismutase, carboxypeptidase Q-precursor and NPC intracellular cholesterol transporter 2 decreased on D18, returning to normal after D28. Albumin, inhibitor of carbonic anhydrase precursor, EGF-like repeat and discoid I-like domain-containing protein 3 and polymeric immunoglobulin receptor increased after insulation. In summary, intermittent scrotal insulation drastically altered ram sperm attributes and seminal proteins, especially those associated with oxidative stress. Knowledge of animal´s response to thermal stress is vital in the scenario of climate changes.

Effect of glucose and reactive oxygen species on boar sperm induced-acrosome exocytosis

Ejaculated boar spermatozoa can be liquid preserved for several days and be easily activated to produce physiological changes. One of the major changes is acrosome exocytosis that is physiologically related to capacitation. Glycolysis and reactive oxygen species (ROS) were studied regarding several boar sperm functions, but data available about their effect on boar sperm acrosome exocytosis are scarce. The objective of this work was to evaluate the effect of glucose and ROS on boar sperm acrosome exocytosis. We evaluated acrosome exocytosis by progesterone induction of capacitated sperm and assess viability, kinematics parameters, ROS levels, ATP content and Protein Kinase A activity in media with or without glucose and hydrogen peroxide or potassium chromate, as source of ROS. Our results show that glucose has no effect on acrosome exocytosis and also, it is not necessary for boar sperm capacitation, although it has a positive effect in the presence of ROS. On the other hand, ROS effects are related to spontaneous acrosome reaction. We conclude that glycolysis may function as a metabolic pathway that provides sustain but is not directly involved in boar sperm acrosome exocytosis and capacitation. Also, ROS do not promote capacitation in boar sperm, but affect spontaneous acrosome exocytosis.

Aquaporins Are Essential to Maintain Motility and Membrane Lipid Architecture During Mammalian Sperm Capacitation

Aquaporins are a family of ubiquitous transmembrane proteins that allow the transport of water and small molecules across the cell plasma membrane. The different members of this family present a characteristic distribution across different cell types, which is species-specific. In mammalian sperm, different AQPs, including AQP3, AQP7, and AQP11, have been identified; their main roles are related to osmoadaptation and sperm motility activation after ejaculation. Capacitation, which is a post-ejaculatory process that sperm must undergo to achieve fertilizing ability, is triggered by pH changes and different extracellular ions that are present in the female reproductive tract. Considering the function of AQPs and their influence on pH through the regulation of water flow, this study aimed to elucidate the potential role of different AQPs during in vitro sperm capacitation using three different transition metal compounds as AQP inhibitors. Cooper sulfate, a specific inhibitor of AQP3, caused a drastic increase in peroxide intracellular levels compared to the control. Mercury chloride, an unspecific inhibitor of all AQPs except AQP7 produced an increase in membrane lipid disorder and led to a decrease in sperm motility and kinetics parameters. Finally, the addition of silver sulfadiazine, an unspecific inhibitor of all AQPs, generated the same effects than mercury chloride, decreased the intracellular pH and altered tyrosine phosphorylation levels after the induction of the acrosome reaction. In the light of the aforementioned, (a) the permeability of AQP3 to peroxides does not seem to be crucial for sperm capacitation and acrosome reaction; (b) AQPs have a key role in preserving sperm motility during that process; and (c) AQPs as a whole seem to contribute to the maintenance of lipid membrane architecture during capacitation and may be related to the intracellular signaling pathways involved in the acrosome reaction. Hence, further research aimed to elucidate the mechanisms underlying the involvement of AQPs in mammalian sperm capacitation and acrosome reaction is warranted.