The Motility of Mouse Spermatozoa Changes Differentially After 30-Minute Exposure Under Simulating Weightlessness and Hypergravity

Research into the mechanisms by which gravity influences spermatozoa has implications for maintaining the species in deep space exploration and may provide new approaches to reproductive technologies on Earth. Changes in the speed of mouse spermatozoa after 30 min exposure to simulated weightlessness (by 3D-clinostat) and 2 g hypergravity (by centrifugation) were studied using inhibitory analysis. Simulated microgravity after 30 min led to an increase in the speed of spermatozoa and against the background of an increase in the relative calcium content in the cytoplasm. This effect was prevented by the introduction of 6-(dimethylamino) purine, wortmannin, and calyculin A. Hypergravity led to a decrease in the speed of spermatozoa movement, which was prevented by sodium orthovanadate and calyculin A. At the same time, under microgravity conditions, there was a redistribution of proteins forming microfilament bundles between the membrane and cytoplasmic compartments and under hypergravity conditions-proteins forming networks. The obtained results indicate that even a short exposure of spermatozoa to altered gravity leads to the launch of mechanotransduction pathways in them and a change in motility.

miR-124-3p regulates the involvement of Ptpn1 in testicular development and spermatogenesis in mouse

Testicular development and spermatogenesis in mouse are a complex process in which phosphorylation modifications and regulation of genes by non-coding RNAs play an important role. However, protein tyrosine phosphatase, non-receptor type 1 (Ptpn1) is widely expressed in mammalian tissues. In this study, we analyzed the expression of Ptpn1 mRNA and its encoded proteins in testicular tissues of juvenile and adult mice by using experimental techniques such as biological information, real-time fluorescence quantitative PCR (RT-qPCR), western blot (WB), immunofluorescence (IF) and transfection, and further analyzed the possible target-regulatory relationship and regulatory mechanisms of miR-124-3p and Ptpn1. We found that Ptpn1 mRNA and its encoded protein were up-regulated in adult mouse testis compared to juvenile mouse testis. The expression trend of miR-124-3p was opposite to that of Ptpn1. In other cell types, Ptpn1 protein is localized in cell membrane, cytoplasm, endoplasmic reticulum and cytoplasmic vesicles. Immunofluorescence showed that Ptpn1 protein was mainly localized in the cytoplasm of male germ cells and was expressed at a high level in early-stage cells (spermatogonia) and at a low level in late-stage cells (sperm). Transfection results showed that the expression levels of Ptpn1 mRNA and its protein were significantly down-regulated after miR-124-3p overexpression in mouse spermatogonia. Bioinformatics analysis showed that Ptpn1 can involved in biological processes such as protein kinase inactivation through peptidyl tyrosine dephosphorylation. The reduction of miR-124-3p may be a key factor in promoting the high expression of Ptpn1 in testicular tissues of adult mice. Increased miR-124-3p may be a key factor in suppressing Ptpn1 expression in the mouse spermatogonia mimics group. The differential expression results from the negative regulation of miR-124-3p.

Sequence level genome-wide associations for bull production and fertility traits in tropically adapted bulls

BACKGROUND

The genetics of male fertility is complex and not fully understood. Male subfertility can adversely affect the economics of livestock production. For example, inadvertently mating bulls with poor fertility can result in reduced annual liveweight production and suboptimal husbandry management. Fertility traits, such as scrotal circumference and semen quality are commonly used to select bulls before mating and can be targeted in genomic studies. In this study, we conducted genome-wide association analyses using sequence-level data targeting seven bull production and fertility traits measured in a multi-breed population of 6,422 tropically adapted bulls. The beef bull production and fertility traits included body weight (Weight), body condition score (CS), scrotal circumference (SC), sheath score (Sheath), percentage of normal spermatozoa (PNS), percentage of spermatozoa with mid-piece abnormalities (MP) and percentage of spermatozoa with proximal droplets (PD).

RESULTS

After quality control, 13,398,171 polymorphisms were tested for their associations with each trait in a mixed-model approach, fitting a multi-breed genomic relationship matrix. A Bonferroni genome-wide significance threshold of 5 × 10^- 8 was imposed. This effort led to identifying genetic variants and candidate genes underpinning bull fertility and production traits. Genetic variants in Bos taurus autosome (BTA) 5 were associated with SC, Sheath, PNS, PD and MP. Whereas chromosome X was significant for SC, PNS, and PD. The traits we studied are highly polygenic and had significant results across the genome (BTA 1, 2, 4, 6, 7, 8, 11, 12, 14, 16, 18, 19, 23, 28, and 29). We also highlighted potential high-impact variants and candidate genes associated with Scrotal Circumference (SC) and Sheath Score (Sheath), which warrants further investigation in future studies.

CONCLUSION

The work presented here is a step closer to identifying molecular mechanisms that underpin bull fertility and production. Our work also emphasises the importance of including the X chromosome in genomic analyses. Future research aims to investigate potential causative variants and genes in downstream analyses.

Could exposure to spaceflight cause mutations in genes that affect male fertility?

Recently, a study reported that upon analyzing blood samples from 14 astronauts that flew Space Transportation System missions between 1998 and 2001, 34 somatic nonsynonymous single nucleotide variants were detected in 17 CH-driver genes. Of interest is that the cohort consisted of relatively young astronauts, 85% of which were males of reproductive age. Having investigated the genes with nonsynonymous substitutes from the literature, it was found that twelve of these 17 genes appear to play essential roles in male reproduction. Changes in telomere length and gene regulation were also reported in another study conducted on an astronaut during a long duration stay on the International Space Station. Realizing the impact of spaceflight on gene sequence with potential influence on male fertility, it is important that more studies are conducted in this field. Specifically, in light of ultimately colonizing space, multi-generational survival is crucial and strategies to mitigate or counteract such effects should be explored.

Genome-wide association study reveals candidate markers related to field fertility and semen quality traits in Holstein-Friesian bulls

In vitro assessment of bull semen quality is routinely used in bull semen processing centres in order to ensure that semen destined to be used in the field has passed minimum standards. Despite these stringent quality control checks, individual bulls that pass the quality control checks can still vary in field fertility by up to 25%. A genome-wide association study was undertaken to determine genetic markers associated with prefreeze and post-thaw bull sperm quality traits as well as field fertility. Genome-wide association analysis was performed using a single nucleotide polymorphism (SNP) regression mixed linear model in WOMBAT. Genes within a 250 Kb span of a suggestive (P ≤ 1 × 10^-5) SNP were considered as candidate genes. One SNP was associated with adjusted pregnancy rate, and 21 SNPs were associated across the seven semen quality traits (P ≤ 1 × 10^-5). Functional candidate genes include SIPA1L2 which was associated with adjusted pregnancy rate. This encodes a Rap GTPase-activating protein involved in Rap1 signalling pathway and was previously found to play a role in the process of sperm differentiation. Gene ontology (GO) analysis also identified significantly enriched biological processes involved protein tyrosine kinase activity including genes such as DYRK1A, TEC and TXK that were associated with sperm motility prior to freezing. Another candidate gene associated with post-thaw sperm motility was FHDC1 which coordinates actin filament and microtubule dynamics. The induced 11 GO terms in the ejaculates rejected after freezing trait were related to ATPase, phosphatase and hydrolase activity. These results reveal novel specific genomic regions and candidate genes associated with economically important phenotypes such as field fertility and semen quality traits.

IKBA phosphorylation governs human sperm motility through ACC-mediated fatty acid beta-oxidation

The nuclear factor-κB (NF-κB) signaling pathway regulates specific immunological responses and controls a wide range of physiological processes. NF-κB inhibitor alpha (IKBA) is an NF-κB inhibitory mediator in the cytoplasm that modulates the nuclear translocation and DNA binding activities of NF-κB proteins. However, whether the upstream cascade of the canonical NF-κB signaling pathway has physiological roles independent of IKBA-mediated transcriptional activation remains unclear. Herein we investigated the function of IKBA in mature sperm in which transcriptional and translational events do not occur. IKBA was highly expressed in human sperm. The repression of IKBA phosphorylation by its inhibitor Bay117082 markedly enhanced sperm motility. On the contrary, lipopolysaccharide-stimulated IKBA phosphorylation significantly decreased sperm motility. Nevertheless, Bay117082 treatment did not affect the motility of IKBA-knockout sperm. Further, untargeted metabolomic analysis and pharmacological blocking assays revealed that the Bay117082-induced increase in sperm motility was attributable to fatty acid β-oxidation (FAO) enhancement. In addition, we found that IKBA phosphorylation inhibition resulted in a significant reduction of acetyl-CoA carboxylase levels in the FAO metabolic pathway. Our findings indicate that IKBA-mediated signaling orchestrates sperm motility program and improves our understanding of transcription-independent NF-κB signaling pathway in cells.

The sperm mitochondria: clues and challenges

Sperm cells rely on different substrates to fulfil thei energy demand for different functions and diverse moments of their life. Species specific mechanism involve both energy substrate transport and their utilization: hexose transporters, a protein family of facilitative passive transporters of glucose and other hexose, have been identified in spermatozoa of different species and, within the species, their localization has been identified and, in some cases, linked to specific glycilitic enzyme presence. The catabolism of hexose sources for energy purposes has been studied in various species, and recent advances has been made in the knowledge of metabolic strategies of sperm cells. In particular, the importance of aerobic metabolism has been defined and described in horse, boar and even mouse spermatozoa; bull sperm cells demonstrate to have a good adaptability and capacity to switch between glycolysis and oxidative phosphorylation; finally, dog sperm cells have been demonstrated to have a great plasticity in energy metabolism management, being also able to activate the anabolic pathway of glycogen syntesis. In conclusion, the study of energy management and mitochondrial function in spermatozoa of different specie furnishes important base knowledge to define new media for preservation as well as newbases for reproductive biotechnologies.

The Autophagy Marker LC3 Is Processed during the Sperm Capacitation and the Acrosome Reaction and Translocates to the Acrosome Where It Colocalizes with the Acrosomal Membranes in Horse Spermatozoa

Despite its importance in somatic cells and during spermatogenesis, little is known about the role that autophagy may play in ejaculated spermatozoa. Our aim was to investigate whether the molecular components of autophagy, such as microtubule-associated protein 1 light chain 3 (LC3), are activated in stallion spermatozoa during the capacitation and acrosome reaction and if this activation could modulate these biological processes. To analyze the autophagy turnover, LC3I and LC3II proteins were assessed by western blotting, and the ratio between both proteins (LC3II/LC3I) was calculated. In somatic cells, this ratio indicates that autophagy has been activated and similar LC3 processing has been described in mammalian spermatozoa. The subcellular localization of autophagy-related proteins was assessed by immunofluorescence with specific antibodies that recognized Atg16, Beclin-1, and LC3. The colocalization of acrosomal membranes (PNA) and LC3 was studied by confocal microcopy, and the acrosome reacted cells were quantified by flow cytometry. The incubation of stallion sperm in capacitating conditions (BWW; 3 h) significantly increased LC3 processing. This increment was three to four times higher after the induction of the acrosome reaction in these cells. LC3 was mainly expressed in the head in mature ejaculated sperm showing a clear redistribution from the post-acrosomal region to the acrosome upon the incubation of sperm in capacitating conditions (BWW, 3 h). After the induction of the acrosome reaction, LC3 colocalized with the acrosome or the apical plasmalemma membranes in the head of the stallion spermatozoa. The inhibition or activation of autophagy-related pathways in the presence of autophagy activators (STF-62247) or inhibitors (E-64d, chloroquine) significantly increased LC3 processing and increased the percent of acrosome reacted cells, whereas 3-methyladenine almost completely inhibited LC3 processing and the acrosome reaction. In conclusion, we found that sperm capacitation and acrosome reaction could be regulated by autophagy components in sperm cells ex vivo by processes that might be independent of the intraluminal pH of the acrosome and dependent of LC3 lipidation. It can be speculated that, in stallion sperm, a form of noncanonical autophagy utilizes some components of autophagy machinery to facilitate the acrosome reaction.

The Stallion Spermatozoa: A Valuable Model to Help Understand the Interplay Between Metabolism and Redox (De)regulation in Sperm Cells

Significance: Proper functionality of the spermatozoa depends on the tight regulation of their redox status; at the same time these cells are highly energy demanding and in the energetic metabolism, principally in the electron transport chain in the mitochondria, reactive oxygen species are continuously produced, in addition to that observed in the Krebs cycle and during the β-oxidation of fatty acids. Recent Advances: In addition, in glycolysis, elimination of phosphate groups from glyceraldehyde 3-phosphate and dihydroxyacetone phosphate results in the byproducts glyoxal (G) and methylglyoxal (MG); these products are 2-oxoaldehydes. The presence of adjacent carbonyl groups makes them strong electrophiles that react with nucleophiles in proteins, lipids, and DNA, forming advanced glycation end products. Critical Issues: This mechanism is behind subfertility in diabetic patients; in the animal breeding industry, commercial extenders for stallion semen contain a supraphysiological concentration of glucose that promotes MG production, constituting a potential model of interest. Future Directions: Increasing our knowledge of sperm metabolism and its interactions with redox regulation may improve current sperm technologies in use, and shall provide new clues to understanding infertility in males. Moreover, stallion spermatozoa due to its accessibility, intense metabolism, and suitability for proteomics/metabolomic studies may constitute a suitable model for studying regulation of metabolism and interactions between metabolism and redox homeostasis. Antioxid. Redox Signal. 37, 521-537.

Sperm of Fruit Fly Drosophila melanogaster under Space Flight

Studies of reproductive function under long-term space flight conditions are of interest in planning the exploration of deep space. Motility, including the use of various inhibitors, cellular respiration, and the content of cytoskeletal proteins were studied, assessing the level of expression of the corresponding genes in spermatozoa of Drosophila melanogaster, which were in space flight conditions for 12 days. The experiment was carried out twice on board the Russian Segment of the International Space Station. Sperm motility speed after space flight, and subsequently 16 h after landing, is reduced relative to the control by 20% (p < 0.05). In comparison with the simulation experiment, we showed that this occurs as a result of the action of overloads and readaptation to the Earth’s gravity. At the same time, cellular respiration, the content of proteins of the respiratory chain, and the expression of their genes do not change. We used kinase inhibitor 6-(dimethylamino)purine (6-DMAP) and phosphatase inhibitors; 6-DMAP restored the reduced the speed of spermatozoa in the flight group to that of the control. These results can be useful in developing a strategy for protecting reproductive health during the development of other bodies in the solar system.

Protective effects of Thai Mucuna pruriens (L.) DC. var. pruriens seeds on sexual behaviors and essential reproductive markers in chronic unpredictable mild stress mice

Background and aims

Chronic stress is a major common cause of male infertility. Many species of velvet beans are shown to be rich in l-DOPA. In Thai folklore medicine, seeds of Mucuna pruriens (L.) DC. var. pruriens (Thai Mhamui or T-MP) have been used for treating erectile dysfunction. This study aimed to determine l-DOPA levels in T-MP seed extract and investigate its preventive on sexual behaviors and reproductive parameter damages including essential proteins in chronic unpredictable mild stress (CUMS) mice.

Experimental procedure

Mice were divided into 4 groups: (I) control, (II) CUMS, (III) T-MP300 + CUMS, and (IV) T-MP600 + CUMS. Groups I and II received DW while groups III and IV were pretreated with the seed extracts (300 and 600 mg/kg BW) for 14 consecutive days before co-treatment with a randomly different CUMS/day (from 12 mild stressors) for 43 days.

Results and conclusion

T-MP seed extract contained l-DOPA approximately 10% of total dried weight. A dose of 600 mg/kg improved sexual performances and degenerative seminiferous epithelium in CUMS mice. Sperm qualities and testosterone level were elevated while corticosterone was decreased in co-treatment groups. T-MP-CUMS cotreated groups also improved expressions of AKAP4, AR, and TyrPho proteins in testis, epididymis, and sperm. T-MP increased StAR and CYP11A1 expressions in testis. It also suppressed testicular apoptosis via decreased expressions of Hsp70, caspases 3, and 9. T-MP seeds containing l-DOPA could improve sexual behaviors and essential reproductive proteins caused by CUMS.

Section

Natural Products.

Taxonomy classification by evise

Traditional Herbal Medicine; Animal Model; Histopathology.

Candidate Genes in Bull Semen Production Traits: An Information Approach Review

Semen quality plays a crucial role in the successful implementation of breeding programs, especially where artificial insemination (AI) is practiced. Bulls with good semen traits have good fertility and can produce a volume of high semen per ejaculation. The aim of this review is to use an information approach to highlight candidate genes and their relation to bull semen production traits. The use of genome-wide association studies (GWAS) has been demonstrated to be successful in identifying genomic regions and individual variations associated with production traits. Studies have reported over 40 genes associated with semen traits using Illumina BeadChip single-nucleotide polymorphism (SNPs).

piR-121380 Is Involved in Cryo-Capacitation and Regulates Post-Thawed Boar Sperm Quality Through Phosphorylation of ERK2 via Targeting PTPN7

Cryopreservation induces capacitation-like (cryo-capacitation) changes, similar to natural capacitation, and affects the fertility potential of post-thawed sperm. The molecular mechanism of sperm cryo-capacitation during cryopreservation remains unknown. PIWI-interacting RNAs (piRNAs) have been reported to be involved in cryo-capacitation of post-thawed sperm and regulation of sperm motility, capacitation, and chemotaxis. In this study, protein tyrosine phosphatase nonreceptor type 7 (PTPN7) was positively targeted by piR-121380 after a dual luciferase assay. The mRNA expression of PTPN7 and piR-121380 was significantly decreased (p < 0.01); however, PTPN7 protein was significantly increased (p < 0.01) in post-thawed boar sperm. Furthermore, E1RK1/2 phosphorylation was reduced during cryopreservation. Six hours after transfection with piR-121380 mimic and inhibitor, the phosphorylation of ERK2 was significantly increased and decreased (p < 0.01), respectively. Furthermore, the highest and lowest total sperm motility, forward motility, and capacitation rate were observed after piR-121380 mimic and inhibitor treatments, respectively. The concentration of intracellular calcium ([Ca2+]i) showed no significant difference after transfection with either piR-121380 mimic or inhibitor at 1, 3, and 6 h. In conclusion, we demonstrated that piR-121380 modulates ERK2 phosphorylation by targeting PTPN7, which induces sperm cryo-capacitation, and eventually affects the motility and fertility potential of post-thawed sperm.

Effect of 2-Cys Peroxiredoxins Inhibition on Redox Modifications of Bull Sperm Proteins

Sperm peroxiredoxins (PRDXs) are moonlighting proteins which, in addition to their antioxidant activity, also act as redox signal transducers through PRDX-induced oxidative post-translational modifications of proteins (oxPTMs). Despite extensive knowledge on the antioxidant activity of PRDXs, the mechanisms related to PRDX-mediated oxPTMs are poorly understood. The present study aimed to investigate the effect of bull sperm 2-Cys PRDX inhibition by Conoidin A on changes in oxPTM levels under control and oxidative stress conditions. The results showed that a group of sperm mitochondrial (LDHAL6B, CS, ACO2, SDHA, ACAPM) and actin cytoskeleton proteins (CAPZB, ALDOA, CCIN) is oxidized due to the action of 2-Cys PRDXs under control conditions. In turn, under oxidative stress conditions, 2-Cys PRDX activity seems to be focused on antioxidant function protecting glycolytic, TCA pathway, and respiratory chain enzymes; chaperones; and sperm axonemal tubulins from oxidative damage. Interestingly, the inhibition of PRDX resulted in oxidation of a group of rate-limiting glycolytic proteins, which is known to trigger the switching of glucose metabolism from glycolysis to pentose phosphate pathway (PPP). The obtained results are expected to broaden the knowledge of the potential role of bull sperm 2-Cys in both redox signal transmission and antioxidant activity.

The transcription factor Sox30 is involved in Nile tilapia spermatogenesis

Spermatogenesis is a complex process in which spermatogonial stem cells differentiate and develop into mature spermatozoa. The transcriptional regulatory network involved in fish spermatogenesis remains poorly understood. Here, we demonstrate in Nile tilapia that the Sox transcription factor family member Sox30 is specifically expressed in the testes and mainly localizes to spermatocytes and spermatids. CRISPR/Cas9-mediated sox30 mutation results in abnormal spermiogenesis, reduction of sperm motility, and male subfertility. Comparative transcriptome analysis shows that sox30 mutation alters the expression of genes involved in spermatogenesis. Further chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq), ChIP-PCR, and luciferase reporter assays reveal that Sox30 positively regulates the transcription of ift140 and ptprb, two genes involved in spermiogenesis, by directly binding to their promoters. Taken together, our data indicate that Sox30 plays essential roles in Nile tilapia spermatogenesis by directly regulating the transcription of the spermiogenesis-related genes ift140 and ptprb.

Mouse and Fly Sperm Motility Changes Differently under Modelling Microgravity

Sperm motility is essential for the natural fertilization process in most animal species. Despite the fact that evolution took place under conditions of constant gravity, the motility of spermatozoa of insects and mammals under microgravity conditions changes in different ways. In this work, an attempt was made to explain this effect. The sperm motility of the fruit fly Drosophila melanogaster and the mouse was evaluated after exposure to a random positioning machine for 6 h. Sodium fluoride was used to inhibit serine/threonine phosphatases, sodium orthovanadate was used to inhibit tyrosine phosphatases, and 6-(dimethylamino)purine was used to inhibit protein kinases. The results obtained indicate that simulated microgravity leads to an increase in the speed of movement of fly spermatozoa by 30% (p < 0.05), and this effect is blocked by sodium fluoride. In contrast, a 29% (p < 0.05) decrease in the speed of movement of mouse spermatozoa under simulated microgravity is prevented by 6-(dimethylamino)purine. Moreover, after 6 h of exposure, the content of tubulin cytoskeleton and actin proteins remains at the control level in the spermatozoa of flies and mice. However, the content of the actin-binding protein alpha-actinin in fly sperm decreases by 29% (p < 0.05), while in mouse sperm, the relative content of alpha-actinin1 increases by 94% (p < 0.05) and alpha-actinin4 by 121% (p < 0.05) relative to the control, as determined by 6 simulated microgravity tests. It can be assumed that the effect of simulated microgravity on the motility of mammalian spermatozoa is mediated through the regulation of phosphorylation and that of insects through the regulation of dephosphorylation of motor proteins; moreover, the development of a response to changes in external mechanical conditions has a different time scale.

The incorporation of cystine by the soluble carrier family 7 member 11 (SLC7A11) is a component of the redox regulatory mechanism in stallion spermatozoa†

Oxidative stress is considered a major mechanism causing sperm damage during cryopreservation and storage, and underlies male factor infertility. Currently, oxidative stress is no longer believed to be caused only by the overproduction of reactive oxygen species, but rather by the deregulation of redox signaling and control mechanisms. With this concept in mind, here, we describe for the first time the presence of the soluble carrier family 7 member 11 (SLC7A11) antiporter, which exchanges extracellular cystine (Cyss) for intracellular glutamate, in stallion spermatozoa, as well as its impact on sperm function using the specific inhibitor sulfasalazine. Spermatozoa incubated with Cyss exhibited an increased intracellular GSH content compared with controls (P < 0.01): 50% in fresh extended stallion spermatozoa and 30% in frozen-thawed spermatozoa. This effect was prevented by the addition of sulfasalazine to the media. Cystine supplementation also reduced the oxidation-reduction potential of spermatozoa, with sulfasalazine only preventing this effect on fresh spermatozoa that were incubated for 3 h at 37°C, but not in frozen-thawed spermatozoa. While sulfasalazine reduced the motility of frozen-thawed spermatozoa, it increased motility in fresh samples. The present findings provide new and relevant data on the mechanism regulating the redox status of spermatozoa and suggest that a different redox regulatory mechanism exists in cryopreserved spermatozoa, thus providing new clues to improve current cryopreservation technologies and treat male factor infertility.

Post-translational modifications of seminal proteins and their importance in male fertility potential

Introduction: The seminal proteome has been shown to directly influence the male fertile potential. Post-translational modifications (PTMs) are significant changes that play a role in the biological regulation of proteins. Sperm cells are transcriptionally and translationally inactive and these modifications are essential to control protein function.Areas covered: Here we reviewed seven PTMs which importance for male reproductive function investigated in the past decade, namely S-nitrosylation and tyrosine nitration (both occurring by the action of NO), glycosylation, ubiquitination, acetylation, methylation, and SUMOylation. Since they were previously identified in human semen, we focus on their role in sperm function, as well as in physiological and pathophysiological processes which could contribute to the fertility potential. The following keywords were applied: 'post-translational modification', 'sperm', 'semen', 'seminal plasma', 'male infertility', 'nitrosylation', 'nitration', 'histone methylation', 'SUMOylation', 'ubiquitination', 'ubiquitilation', 'glycosylation', and 'acetylation'.Expert opinion: Most biological processes orchestrated by proteins require PTMs for their activation or inhibition. Most of them are dynamic and occur in mature sperm, modulating protein function, thus exerting a significant role in sperm function and fertility. Finally, the study of PTMs should be also addressed in pathophysiological processes, as different clinical conditions are known to alter the proteome.

Redox Regulation and Oxidative Stress: The Particular Case of the Stallion Spermatozoa

Redox regulation and oxidative stress have become areas of major interest in spermatology. Alteration of redox homeostasis is recognized as a significant cause of male factor infertility and is behind the damage that spermatozoa experience after freezing and thawing or conservation in a liquid state. While for a long time, oxidative stress was just considered an overproduction of reactive oxygen species, nowadays it is considered as a consequence of redox deregulation. Many essential aspects of spermatozoa functionality are redox regulated, with reversible oxidation of thiols in cysteine residues of key proteins acting as an “on–off” switch controlling sperm function. However, if deregulation occurs, these residues may experience irreversible oxidation and oxidative stress, leading to malfunction and ultimately death of the spermatozoa. Stallion spermatozoa are “professional producers” of reactive oxygen species due to their intense mitochondrial activity, and thus sophisticated systems to control redox homeostasis are also characteristic of the spermatozoa in the horse. As a result, and combined with the fact that embryos can easily be collected in this species, horses are a good model for the study of redox biology in the spermatozoa and its impact on the embryo.

The calcium-sensing receptor regulates protein tyrosine phosphorylation through PDK1 in boar spermatozoa

Regulation of protein tyrosine phosphorylation is required for sperm capacitation and oocyte fertilization. The objective of the present work was to study the role of the calcium-sensing receptor (CaSR) on protein tyrosine phosphorylation in boar spermatozoa under capacitating conditions. To do this, boar spermatozoa were incubated in Tyrode's complete medium for 4 hr and the specific inhibitor of the CaSR, NPS2143, was used. Also, to study the possible mechanism(s) by which this receptor exerts its function, spermatozoa were incubated in the presence of specific inhibitors of the 3-phosphoinositide dependent protein kinase 1 (PDK1) and protein kinase A (PKA). Treatment with NPS2143, GSK2334470, an inhibitor of PDK1 and H-89, an inhibitor of PKA separately induced an increase in tyrosine phosphorylation of 18 and 32 kDa proteins, a decrease in the serine/threonine phosphorylation of the PKA substrates together with a drop in sperm motility and viability. The present work proposes a new signalling pathway of the CaSR, mediated by PDK1 and PKA in boar spermatozoa under capacitating conditions. Our results show that the inhibition of the CaSR induces the inhibition of PDK1 that blocks PKA activity resulting in a rise in tyrosine phosphorylation of p18 and p32 proteins. This novel signalling pathway has not been described before and could be crucial to understand boar sperm capacitation within the female reproductive tract.

Effect of Aminopeptidase N on functions and fertility of mouse spermatozoa in vitro

Aminopeptidase N (APN) is defined as a multifunctional enzyme, which regulate cellular physiology of a wide variety of cells in human. Earlier studies reported that mammalian semen shares this common enzyme as a major protein of seminal plasma that has correlation with male fertility, while the regulatory mechanisms of APN in spermatozoa are still far from being well understood. Present study was designed to investigate the role of APN in biological and chemical functions of spermatozoa using an in vitro antagonistic approach. Results showed that lower APN activity in sperm culture medium significantly increased sperm motility and the percentage of high speed spermatozoa and decreased the percentage of slow speed spermatozoa after a dose dependent inhibitor treatment (10, 100, and 1000 μM leuhistin) on epididymal mouse spermatozoa in a capacitating media for 90 min. Both 100 μM and 1000 μM decreased APN activity, while only 1000 μM decreased cell viability and increased PKA activity significantly compared to control. Nonetheless capacitation status, acrosome reaction status, and lactate dehydrogenase activity were not affected. Intriguingly, the treatment affected embryonic development through decreasing tyrosine phosphorylation of proteins and increasing reactive oxygen species levels. Further in silico analysis revealed associated regulatory proteins, which have critical functional role for male fertility.

A parental requirement for dual-specificity phosphatase 6 in zebrafish

Background

Signaling cascades, such as the extracellular signal-regulated kinase (ERK) pathway, play vital roles in early vertebrate development. Signals through these pathways are initiated by a growth factor or hormone, are transduced through a kinase cascade, and result in the expression of specific downstream genes that promote cellular proliferation, growth, or differentiation. Tight regulation of these signals is provided by positive or negative modulators at varying levels in the pathway, and is required for proper development and function. Two members of the dual-specificity phosphatase (Dusp) family, dusp6 and dusp2, are believed to be negative regulators of the ERK pathway and are expressed in both embryonic and adult zebrafish, but their specific roles in embryogenesis remain to be fully understood.

Results

Using CRISPR/Cas9 genome editing technology, we generated zebrafish lines harboring germ line deletions in dusp6 and dusp2. We do not detect any overt defects in dusp2 mutants, but we find that approximately 50% of offspring from homozygous dusp6 mutants do not proceed through embryonic development. These embryos are fertilized, but are unable to proceed past the first zygotic mitosis and stall at the 1-cell stage for several hours before dying by 10 h post fertilization. We demonstrate that dusp6 is expressed in gonads of both male and female zebrafish, suggesting that loss of dusp6 causes defects in germ cell production. Notably, the 50% of homozygous dusp6 mutants that complete the first cell division appear to progress through embryogenesis normally and give rise to fertile adults.

Conclusions

The fact that offspring of homozygous dusp6 mutants stall prior to activation of the zygotic genome, suggests that loss of dusp6 affects gametogenesis and/or parentally-directed early development. Further, since only approximately 50% of homozygous dusp6 mutants are affected, we postulate that ERK signaling is tightly regulated and that dusp6 is required to keep ERK signaling within a range that is permissive for proper embryogenesis. Lastly, since dusp6 is expressed throughout zebrafish embryogenesis, but dusp6 mutants do not exhibit defects after the first cell division, it is possible that other regulators of the ERK pathway compensate for loss of dusp6 at later stages.

Electronic supplementary material

The online version of this article (10.1186/s12861-018-0164-6) contains supplementary material, which is available to authorized users.

MicroRNA in sperm from Duroc, Landrace and Yorkshire boars

Sperm contain microRNAs (miRNAs), which may have roles in epigenetic control. Regarding phylogenetic relationships among various swine breeds, Yorkshire and Landrace, are considered phenotypically and genetically very similar, but distinctly different from Duroc. The objective of the present study was to compare abundance of boar sperm miRNAs in these three breeds. Overall, 252 prioritized miRNAs were investigated using real-time PCR; relative expression of miRNAs in sperm was similar in Yorkshire and Landrace boars, but significantly different compared to Duroc. Seventeen miRNAs (hsa-miR-196a-5p, hsa-miR-514a-3p, hsa-miR-938, hsa-miR-372-3p, hsa-miR-558, hsa-miR-579-3p, hsa-miR-595, hsa-miR-648, hsa-miR-524-3p, hsa-miR-512-3p, hsa-miR-429, hsa-miR-639, hsa-miR-551a, hsa-miR-624-5p, hsa-miR-585-3p, hsa-miR-508-3p and hsa-miR-626) were down-regulated (P < 0.05; fold regulation ≤-2) in Yorkshire and Landrace sperm, compared to Duroc sperm. Furthermore, three miRNAs (hsa-miR-9-5p, hsa-miR-150-5p, and hsa-miR-99a-5p) were significantly up-regulated in Yorkshire and Landrace sperm compared to Duroc sperm, However, 240 miRNAs were not significantly different (within + 2 fold) between Yorkshire and Landrace sperm. We concluded that miRNAs in sperm were not significantly different between Yorkshire and Landrace boars, but there were significant differences between those two breeds and Duroc boars. Furthermore, integrated target genes for selected down-regulated miRNAs (identified via an in-silico method) appeared to participate in spermatogenesis and sperm functions.

Depletion of Intracellular Thiols and Increased Production of 4-Hydroxynonenal that Occur During Cryopreservation of Stallion Spermatozoa Lead to Caspase Activation, Loss of Motility, and Cell Death

Oxidative stress has been linked to sperm death and the accelerated senescence of cryopreserved spermatozoa. However, the molecular mechanisms behind this phenomenon remain poorly understood. Reactive oxygen species (ROS) are considered relevant signaling molecules for sperm function, only becoming detrimental when ROS homeostasis is lost. We hereby hypothesize that a major component of the alteration of ROS homeostasis in cryopreserved spermatozoa is the exhaustion of intrinsic antioxidant defense mechanisms. To test this hypothesis, semen from seven stallions was frozen using a standard technique. The parameters of sperm quality (motility, velocity, and membrane integrity) and markers of sperm senescence (caspase 3, 4-hydroxynonenal, and mitochondrial membrane potential) were assessed before and after cryopreservation. Changes in the intracellular thiol content were also monitored. Cryopreservation caused significant increases in senescence markers as well as dramatic depletion of intracellular thiols to less than half of the initial values (P < 0.001) postthaw. Interestingly, very high and positive correlations were observed among thiol levels with sperm functionality postthaw: total motility (r = 0.931, P < 0.001), progressive motility (r = 0.904, P < 0.001), and percentage of live spermatozoa without active caspase 3 (r = 0.996, P < 0.001). In contrast, negative correlations were detected between active caspase 3 and thiol content both in living (r = -0.896) and dead (r = -0.940) spermatozoa; additionally, 4-hydroxynonenal levels were negatively correlated with thiol levels (r = -0.856). In conclusion, sperm functionality postthaw correlates with the maintenance of adequate levels of intracellular thiols. The accelerated senescence of thawed spermatozoa is related to oxidative and electrophilic stress induced by increased production of 4-hydroxynoneal in thawed samples once intracellular thiols are depleted.

Inhibition of Mitochondrial Complex I Leads to Decreased Motility and Membrane Integrity Related to Increased Hydrogen Peroxide and Reduced ATP Production, while the Inhibition of Glycolysis Has Less Impact on Sperm Motility

Mitochondria have been proposed as the major source of reactive oxygen species in somatic cells and human spermatozoa. However, no data regarding the role of mitochondrial ROS production in stallion spermatozoa are available. To shed light on the role of the mitochondrial electron transport chain in the origin of oxidative stress in stallion spermatozoa, specific inhibitors of complex I (rotenone) and III (antimycin-A) were used. Ejaculates from seven Andalusian stallions were collected and incubated in BWW media at 37 °C in the presence of rotenone, antimycin-A or control vehicle. Incubation in the presence of these inhibitors reduced sperm motility and velocity (CASA analysis) (p<0.01), but the effect was more evident in the presence of rotenone (a complex I inhibitor). These inhibitors also decreased ATP content. The inhibition of complexes I and III decreased the production of reactive oxygen species (p<0.01) as assessed by flow cytometry after staining with CellRox deep red. This observation suggests that the CellRox probe mainly identifies superoxide and that superoxide production may reflect intense mitochondrial activity rather than oxidative stress. The inhibition of complex I resulted in increased hydrogen peroxide production (p<0.01). The inhibition of glycolysis resulted in reduced sperm velocities (p<0.01) without an effect on the percentage of total motile sperm. Weak and moderate (but statistically significant) positive correlations were observed between sperm motility, velocity and membrane integrity and the production of reactive oxygen species. These results indicate that stallion sperm rely heavily on oxidative phosphorylation (OXPHOS) for the production of ATP for motility but also require glycolysis to maintain high velocities. These data also indicate that increased hydrogen peroxide originating in the mitochondria is a mechanism involved in stallion sperm senescence.

The Impact of Reproductive Technologies on Stallion Mitochondrial Function

The traditional assessment of stallion sperm comprises evaluation of sperm motility and membrane integrity and identification of abnormal morphology of the spermatozoa. More recently, the progressive introduction of flow cytometry is increasing the number of tests available. However, compared with other sperm structures and functions, the evaluation of mitochondria has received less attention in stallion andrology. Recent research indicates that sperm mitochondria are key structures in sperm function suffering major changes during biotechnological procedures such as cryopreservation. In this paper, mitochondrial structure and function will be reviewed in the stallion, when possible specific stallion studies will be discussed, and general findings on mammalian mitochondrial function will be argued when relevant. Especial emphasis will be put on their role as source of reactive oxygen species and in their role regulating sperm lifespan, a possible target to investigate with the aim to improve the quality of frozen-thawed stallion sperm. Later on, the impact of current sperm technologies, principally cryopreservation, on mitochondrial function will be discussed pointing out novel areas of research interest with high potential to improve current sperm technologies.

Phosphorylated AKT preserves stallion sperm viability and motility by inhibiting caspases 3 and 7

AKT, also referred to as protein kinase B (PKB or RAC), plays a critical role in controlling cell survival and apoptosis. To gain insights into the mechanisms regulating sperm survival after ejaculation, the role of AKT was investigated in stallion spermatozoa using a specific inhibitor and a phosphoflow approach. Stallion spermatozoa were washed and incubated in Biggers–Whitten–Whittingham medium, supplemented with 1% polyvinyl alcohol (PVA) in the presence of 0 (vehicle), 10, 20 or 30 μM SH5, an AKT inhibitor. SH5 treatment reduced the percentage of sperm displaying AKT phosphorylation, with inhibition reaching a maximum after 1 h of incubation. This decrease in phosphorylation was attributable to either dephosphorylation or suppression of the active phosphorylation pathway. Stallion spermatozoa spontaneously dephosphorylated during in vitro incubation, resulting in a lack of a difference in AKT phosphorylation between the SH5-treated sperm and the control after 4 h of incubation. AKT inhibition decreased the proportion of motile spermatozoa (total and progressive) and the sperm velocity. Similarly, AKT inhibition reduced membrane integrity, leading to increased membrane permeability and reduced the mitochondrial membrane potential concomitantly with activation of caspases 3 and 7. However, the percentage of spermatozoa exhibiting oxidative stress, the production of mitochondrial superoxide radicals, DNA oxidation and DNA fragmentation were not affected by AKT inhibition. It is concluded that AKT maintains the membrane integrity of ejaculated stallion spermatozoa, presumably by inhibiting caspases 3 and 7, which prevents the progression of spermatozoa to an incomplete form of apoptosis.

Free Spanish abstract

A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/148/2/221/suppl/DC1.

Caspase activation, hydrogen peroxide production and Akt dephosphorylation occur during stallion sperm senescence

To investigate the mechanisms inducing sperm death after ejaculation, stallion ejaculates were incubated in BWW media during 6 h at 37°C. At the beginning of the incubation period and after 1, 2, 4 and 6 h sperm motility and kinematics (CASA), mitochondrial membrane potential and membrane permeability and integrity were evaluated (flow cytometry). Also, at the same time intervals, active caspase 3, hydrogen peroxide, superoxide anion (flow cytometry) and Akt phosphorylation (flow cytometry) were evaluated. Major decreases in sperm function occurred after 6 h of incubation, although after 1 h decrease in the percentages of motile and progressive motile sperm occurred. The decrease observed in sperm functionality after 6 h of incubation was accompanied by a significant increase in the production of hydrogen peroxide and the greatest increase in caspase 3 activity. Additionally, the percentage of phosphorylated Akt reached a minimum after 6 h of incubation. These results provide evidences that sperm death during in vitro incubation is largely an apoptotic phenomena, probably stimulated by endogenous production of hydrogen peroxide and the lack of prosurvival factors maintaining Akt in a phosphorylated status. Disclosing molecular mechanisms leading to sperm death may help to develop new strategies for stallion sperm conservation.

Genome-wide association study for poor sperm motility in Holstein-Friesian bulls

The aim of the study was to screen the whole bull genome to identify markers and candidate genes underlying poor sperm motility. The analyzed data set originates from the Polish Holstein-Friesian bull population and consists of 41 Case and 279 Control bulls (selected from 1581 bulls). The most distinguishing trait of case group was very poor sperm motility (average 25.61%) when compared to control samples (average 72.95%). Each bull was genotyped using the Illumina BovineSNP50 BeadChip. Genome-wide association analysis was performed with the use of GoldenHelix SVS7 software. An additive model with a Cohran-Armitage test, Correlation/Trend adjusted by Bonferroni test were used to estimate the effect of Single Nucleotide Polymorphism (SNP) marker for poor sperm motility. Markers (n=34) reached genome-wide significance. The most significant SNP were located on chromosome 24 (rs110876480), 5 (rs110827324 and rs29011704), and 1 (rs110596818), in the close vicinity of melanocortin 4 receptor (MC4R), PDZ domain containing ring finger 4 (PDZRN4) and ethanolamine kinase 1 (ETNK1), olfactory receptor 5K3-like (LOC785875) genes, respectively. For five other candidate genes located close to significant markers (in distance of ca. 1 Mb), namely alkaline phosphatase, liver/bone/kidney (ALPL), tripartite motif containing 36 (TRIM36), 3-hydroxyisobutyrate dehygrogenase (HIBADH), kelch-like 1 (KLHL1), protein kinase C, beta (PRKCB), their potential role in sperm motility was confirmed in the earlier studies. Five additional candidate genes, cystic fibrosis transmembrane conductance regulator (CFTR), insulin-like growth factor 1 receptor (IGF1R), steroid-5-alpha-reductase, alpha polypeptide 2 (SRD5A2), cation channel, sperm associated 1 (CATSPER1) calpain 1 (mu/I) large subunit (CAPN1) were suggested to be significantly associated with sperm motility or semen biochemistry. Results of the present study indicate there is a genetic complexity of poor sperm motility but also indicate there might be a causal polymorphism useful in marker-assisted selection. Identifying genomic regions associated with poor sperm motility may be very important for early recognition of a young sire as unsuitable for effective semen production in artificial insemination centers.

During cooled storage the extender influences processed autophagy marker light chain 3 (LC3B) of stallion spermatozoa

To investigate the role of the processed autophagy marker light chain 3 (LC3B) protein in sperm survival in stallion semen processing during cooled storage, split ejaculates were diluted in two different extenders, KMT and INRA 96, and LC3B processing and sperm quality evaluated during incubation at 5°C for five days. After 3 days of incubation there was a drop in total motility in both extenders, although the percentage of progressive motile sperm was greater (P<0.05) in samples extended in INRA96. On Day 5 of cooled storage all sperm parameters decreased significantly independent of the extender, however, samples extended in INRA 96 maintained motility values while those extended in KMT had a further decrease in motility compared with data collected on Day 3 of incubation. The percentage of live sperm decreased over the time of incubation, but only in samples incubated in KMT. The extender had a marked effect in LC3B processing during cooled storage. Spermatozoa maintained in KMT extender did not exhibit LC3B processing, while in spermatozoa incubated in INRA96 there was an increase (P<0.01) in LC3B processing after 5 days of cooled storage. Stallion spermatozoa experience LC3B turnover during cooled storage, however, the extent depends on the extender used. Apparently LC3B turnover is associated with enhanced survival.

Evolutionary conservation of mammalian sperm proteins associates with overall, not tyrosine, phosphorylation in human spermatozoa

We investigated possible associations between sequence evolution of mammalian sperm proteins and their phosphorylation status in humans. As a reference, spermatozoa from three normozoospermic men were analyzed combining two-dimensional gel electrophoresis, immunoblotting, and mass spectrometry. We identified 99 sperm proteins (thereof 42 newly described) and determined the phosphorylation status for most of them. Sequence evolution was studied across six mammalian species using nonsynonymous/synonymous rate ratios (dN/dS) and amino acid distances. Site-specific purifying selection was assessed employing average ratios of evolutionary rates at phosphorylated versus nonphosphorylated amino acids (α). According to our data, mammalian sperm proteins do not show statistically significant sequence conservation difference, no matter if the human ortholog is a phosphoprotein with or without tyrosine (Y) phosphorylation. In contrast, overall phosphorylation of human sperm proteins, i.e., phosphorylation at serine (S), threonine (T), and/or Y residues, associates with above-average conservation of sequences. Complementary investigations suggest that numerous protein-protein interactants constrain sequence evolution of sperm phosphoproteins. Although our findings reject a special relevance of Y phosphorylation for sperm functioning, they still indicate that overall phosphorylation substantially contributes to proper functioning of sperm proteins. Hence, phosphorylated sperm proteins might be considered as prime candidates for diagnosis and treatment of reduced male fertility.

"Omics" of human sperm: profiling protein phosphatases

Phosphorylation is a major regulatory mechanism in eukaryotic cells performed by the concerted actions of kinases and phosphatases (PPs). Protein phosphorylation has long been relevant to sperm physiology, from acquisition of motility in the epididymis to capacitation in the female reproductive tract. While the precise kinases involved in the regulation of sperm phosphorylation have been studied for decades, the PPs have only recently received research interest. Tyrosine phosphorylation was first implicated in the regulation of several sperm-related functions, from capacitation to oocyte binding. Only afterwards, in 1996, the inhibition of the serine/threonine-PP phosphoprotein phosphatase 1 (PPP1) by okadaic acid and calyculin-A was shown to initiate motility in caput epididymal sperm. Today, the current mechanisms of sperm motility acquisition based on PPP1 and its regulators are still far from being fully understood. PPP1CC2, specifically expressed in mammalian sperm, has been considered to be the only sperm-specific serine/threonine-PP, while other PPP1 isoforms were thought to be absent from sperm. This article examines the "Omics" of human sperm, and reports, for the first time, the identification of three new serine/threonine-protein PPs, PPP1CB, PPP4C, and PPP6C, in human sperm, together with two tyrosine-PPs, MKP1 and PTP1C. We specifically localized in sperm PPP1CB and PPP1CC2 from the PPP1 subfamily, and PPP2CA, PPP4C, and PPP6C from the PPP2 subfamily of the serine/threonine-PPs. A semi-quantitative analysis was performed to determine the various PPs' differential expression in sperm head and tail. These findings contribute to a comprehensive understanding of human sperm PPs, and warrant further research for their clinical and therapeutic significance.

Spermatozoa motility and variation in the seminal plasma proteome of Eurasian perch (Perca fluviatilis) during the reproductive season

This study evaluated physiological and functional sperm parameters and the seminal plasma proteome of Eurasian perch (Perca fluviatilis) over the course of their reproductive season. Spermatozoa velocity (169.56 ± 6.53 to 158.5 ± 7.4 µm sec(-1)), percent motility (95.89 ± 4.28% to 89.55 ± 4.5%), and osmolality of seminal plasma (290 ± 5 to 297 ± 12 mOsmol kg(-1)) remained stable throughout the reproductive season. Milt volume and protein concentration of seminal plasma gradually increased and reached the highest values late in the reproductive period. Spermatozoa concentration peaked in the mid-reproductive season (66.90 ± 13 × 10(9)  spermatozoa ml(-1)) and decreased towards the end (54 ± 10 × 10(9)  spermatozoa ml(-1)). A proteomic analysis of seminal plasma using two-dimensional polyacrylamide gel electrophoresis revealed 10 protein spots significantly altered over the course of the reproductive season. Subsequent protein characterization suggested that time in the reproductive season predominantly affected proteins involved in membrane trafficking, organization, cell motility, and oxido-reductase activity. This study provides new data on physiological properties of sperm and protein patterns of seminal plasma over the course of the reproductive season that should be considered in the development of methods for artificial reproduction of perch.

Identification and function of exchange proteins activated directly by cyclic AMP (Epac) in mammalian spermatozoa

The role of cAMP in spermatic functions was classically thought to be mediated exclusively through the activation of Protein Kinase A (PKA). However, it has recently been shown that cAMP also exerts its effects through a PKA-independent pathway activating a family of proteins known as Epac proteins. Therefore, many of the spermatic functions thought to be regulated by cAMP through the activation of PKA are again under study. We aimed to identify and to investigate the role of Epac proteins in spermatozoa using a specific permeable analog (8-Br-2′-O-Me-cAMP). Also, we aimed to study its relationship with E-cadherin, an adhesion protein involved in fertility. Our results demonstrate the presence and sub-cellular distribution of Epac 1 and Epac 2 in mammalian spermatozoa. Capacitation and the acrosome reaction induced a change in the localization of Epac proteins in sperm. Moreover, incubation with 8-Br-2′-O-Me-cAMP prompted an increase in Rap1 activation, in the scrambling of plasma membrane phospholipids (necessary for the capacitation process), the acrosome reaction, motility, and calcium mobilization, when spermatozoa were incubated in acrosome reaction conditions. Finally, the activation of Epac proteins induced a change in the distribution of E-cadherin. Therefore, the increase in the acrosome reaction, together with the increase in calcium (which is known to be essential for fertilization) and the Epac nteraction with E-cadherin, might indicate that Epac proteins have an important role in gamete recognition and fertilization.

Resveratrol mobilizes Ca2+ from intracellular stores and induces c-Jun N-terminal kinase activation in tumoral AR42J cells

Resveratrol (3,4',5-trihydroxy-trans-stilbene), a phytoalexin naturally found in grapes and red wine, is a redox-active compound endowed with significant positive activities. In this study, the effects of resveratrol on intracellular free Ca(2+) concentration ([Ca(2+)](c)) and on cell viability in tumoral AR42J pancreatic cells are examined. The results show that resveratrol (100 μM and 1 mM) induced changes in [Ca(2+)](c), that consisted of single or short lasting spikes followed by a slow reduction toward a value close to the resting level. Lower concentrations of resveratrol (1 and 10 μM) did not show detectable effects on [Ca(2+)](c). Depletion of intracellular Ca(2+) stores by stimulation of cells with 1 nM CCK-8, 20 pM CCK-8 or 1 μM thapsigargin, blocked Ca(2+) responses evoked by resveratrol. Conversely, prior stimulation of cells with resveratrol inhibited Ca(2+) mobilization in response to a secondary application of CCK-8 or thapsigargin. In addition, resveratrol inhibited oscillations in [Ca(2+)](c) evoked by a physiological concentration of CCK-8 (20 pM). On the other hand, incubation of cells in the presence of resveratrol induced a reduction of cell viability. Finally, incubation of AR42J cells in the presence of resveratrol led to activation of c-Jun N-terminal kinase (JNK), a mitogen-activated protein kinase responsive to stress stimuli. Activation of JNK was reduced in the absence of extracellular Ca(2+). In summary, the results show that resveratrol releases Ca(2+) from intracellular stores, most probably from the endoplasmic reticulum, and reduces AR42J cells viability. Reorganization of cell's survival/death processes in the presence of resveratrol may involve Ca(2+)-mediated JNK activation.

Autophagy and apoptosis have a role in the survival or death of stallion spermatozoa during conservation in refrigeration

Apoptosis has been recognized as a cause of sperm death during cryopreservation and a cause of infertility in humans, however there is no data on its role in sperm death during conservation in refrigeration; autophagy has not been described to date in mature sperm. We investigated the role of apoptosis and autophagy during cooled storage of stallion spermatozoa. Samples from seven stallions were split; half of the ejaculate was processed by single layer centrifugation, while the other half was extended unprocessed, and stored at 5°C for five days. During the time of storage, sperm motility (CASA, daily) and membrane integrity (flow cytometry, daily) were evaluated. Apoptosis was evaluated on days 1, 3 and 5 (active caspase 3, increase in membrane permeability, phosphatidylserine translocation and mitochondrial membrane potential) using flow cytometry. Furthermore, LC3B processing was investigated by western blotting at the beginning and at the end of the period of storage. The decrease in sperm quality over the period of storage was to a large extent due to apoptosis; single layer centrifugation selected non-apoptotic spermatozoa, but there were no differences in sperm motility between selected and unselected sperm. A high percentage of spermatozoa showed active caspase 3 upon ejaculation, and during the period of storage there was an increase of apoptotic spermatozoa but no changes in the percentage of live sperm, revealed by the SYBR-14/PI assay, were observed. LC3B was differentially processed in sperm after single layer centrifugation compared with native sperm. In processed sperm more LC3B-II was present than in non-processed samples; furthermore, in non-processed sperm there was an increase in LC3B-II after five days of cooled storage. These results indicate that apoptosis plays a major role in the sperm death during storage in refrigeration and that autophagy plays a role in the survival of spermatozoa representing a new pro-survival mechanism in spermatozoa not previously described.

Comparative transcriptome sequencing of germline and somatic tissues of the Ascaris suum gonad

Background

Ascaris suum (large roundworm of pigs) is a parasitic nematode that causes substantial losses to the meat industry. This nematode is suitable for biochemical studies because, unlike C. elegans, homogeneous tissue samples can be obtained by dissection. It has large sperm, produced in great numbers that permit biochemical studies of sperm motility. Widespread study of A. suum would be facilitated by more comprehensive genome resources and, to this end, we have produced a gonad transcriptome of A. suum.

Results

Two 454 pyrosequencing runs generated 572,982 and 588,651 reads for germline (TES) and somatic (VAS) tissues of the A. suum gonad, respectively. 86% of the high-quality (HQ) reads were assembled into 9,955 contigs and 69,791 HQ reads remained as singletons. 2.4 million bp of unique sequences were obtained with a coverage that reached 16.1-fold. 4,877 contigs and 14,339 singletons were annotated according to the C. elegans protein and the Kyoto Encyclopedia of Genes and Genomes (KEGG) protein databases. Comparison of TES and VAS transcriptomes demonstrated that genes participating in DNA replication, RNA transcription and ubiquitin-proteasome pathways are expressed at significantly higher levels in TES tissues than in VAS tissues. Comparison of the A. suum TES transcriptome with the C. elegans microarray dataset identified 165 A. suum germline-enriched genes (83% are spermatogenesis-enriched). Many of these genes encode serine/threonine kinases and phosphatases (KPs) as well as tyrosine KPs. Immunoblot analysis further suggested a critical role of phosphorylation in both testis development and spermatogenesis. A total of 2,681 A. suum genes were identified to have associated RNAi phenotypes in C. elegans, the majority of which display embryonic lethality, slow growth, larval arrest or sterility.

Conclusions

Using deep sequencing technology, this study has produced a gonad transcriptome of A. suum. By comparison with C. elegans datasets, we identified sets of genes associated with spermatogenesis and gonad development in A. suum. The newly identified genes encoding KPs may help determine signaling pathways that operate during spermatogenesis. A large portion of A. suum gonadal genes have related RNAi phenotypes in C. elegans and, thus, might be RNAi targets for parasite control.

Melatonin reduces lipid peroxidation and apoptotic-like changes in stallion spermatozoa

Lipid peroxidation (LPO) has been claimed as a major factor involved in stallion damage during storage or cryopreservation. Because melatonin is a well-known potent antioxidant, the aim of the present study was to investigate the effect of melatonin during in vitro incubation. Furthermore, we investigated the presence of specific melatonin receptors (MT1 and MT2) using specific polyclonal antibodies and western blotting. Stallion spermatozoa were incubated up to 3 hr at 37°C in the presence of different concentrations of melatonin (0, 50 pm, 100 pm, 200 pm, or 1 μm). At the beginning and at the end of the incubation period, sperm motility (using computer-assisted sperm analysis), membrane integrity and permeability, fluidity of the sperm membrane, LPO, and mitochondrial membrane potential (Δψm) were flow cytometrically evaluated. Melatonin reduced changes in the spermatozoa related to apoptosis (increased sperm membrane permeability and lowered Δψm) (P < 0.05). Furthermore, LPO was dramatically reduced (P < 0.01) while no effect was observed on sperm motility or kinematics. Interestingly, melatonin helped maintain a more fluid sperm plasmalemma (P < 0.05). Our results clearly show the absence of MT1 and MT2 receptors in the stallion spermatozoa. It is concluded that melatonin is a useful tool to improve the quality of stored stallion sperm, increasing their life span and reducing premature aging, this likely relates to melatonin's antioxidant properties.

Glucose and fructose as functional modulators of overall dog, but not boar sperm function

The main aim of the present work was to test the effects of glucose and fructose on the phosphorylation levels of proteins linked to the control of overall sperm function in two species with very different metabolic characteristics, dog and boar. Incubation of dog spermatozoa with 10mM glucose increased serine phosphorylation of proteins related to cell cycle and signal transduction including cyclins B and E, Cdk2, Cdk6, Cdc6, PYK2, c-kit, Raf-1, TRK and several protein phosphatases. Incubation of dog spermatozoa with 10mM fructose decreased serine phosphorylation levels of cyclins B and D3, Cdk1/Cdc2, Cdk2, Cdk6, Akt, PI3 kinase, ERK-1 and protein kinase C. Incubation of boar spermatozoa with glucose or fructose did not modify any of the phosphorylation patterns studied. Given that one important difference between dog and boar spermatozoa is the presence of glucokinase (GK) in dog but not in boar, GK-transfected COS7 cells were incubated with either 10mM glucose or 10mM fructose. Incubation of GK-transfected cells with fructose decreased serine phosphorylation of cyclin A, ERK-2 and Hsp-70. In contrast, incubation of control COS7 cells with fructose increased serine phosphorylation of Cdk6, Cdk1/Cdc2, protein kinase C and Hsp-70. Incubation with glucose did not induce any significant effect. Our results indicate that monosaccharides act as signalling compounds in dog spermatozoa after ejaculation through changes in the phosphorylation levels of specific proteins. One of the factors that may be related to the action of sugars is the equilibrium of the total sperm hexokinase activity, in which the presence or absence of GK appears to be relevant.

Protein tyrosine phosphatase non-receptor type 14 is a novel sperm-motility biomarker

PURPOSE

To understand the molecular basis of sperm-motility and to identify related novel motility biomarkers.

METHODS

Two-dimensional electrophoresis (2DE) followed by Reverse-phase-nano-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (RP-nano-HPLC-ESI-MS/MS) were applied to establish the human sperm proteome. Then the sperm proteome of moderate-motile human sperm fraction and that of good-motile human sperm fraction from pooled spermatozoa of forty normozoospermic donors (Group 1 subjects) were compared to identify the dysregulated proteins. Among these down-regulated proteins, Protein tyrosine phosphatase non-receptor type 14 (PTPN14) was chosen to reconfirm by Western blotting and semi-quantitative reverse transcription polymerase chain reaction. For clinical application, Western blotting and real-time reverse transcription polymerase chain reaction was performed to compare the expression level of PTPN14 in (Group 2 subjects) nine normozoospermic controls and thirty-three asthenozoospermic patients (including 21 mild asthenozoospermic cases and 12 severe cases). Finally, bioinformatic tools prediction and immunofluorescence assay were performed to elucidate the potential localization of PTPN14.

RESULTS

The expression levels of three proteins were observed to be lower in the moderate-motile sperm fraction than in good-motile sperm of group 1 subjects. Among three proteins with persistent down-regulation in the moderate-motile sperm, we reconfirmed that the expression level of PTPN14 was significantly lower in both mRNA and protein levels from the moderate-motile sperm fraction. Further, down-regulation of PTPN14 was found at the translational and transcriptional level in the asthenozoospermic men. Finally, Bioinformatic tools prediction and immunofluorescence assay showed that PTPN14 maybe predominantly localized at the mitochondria in the midpiece of human ejaculated sperm.

CONCLUSIONS

Proteomics tools were applied to identify three possible sperm motility-related proteins. Among these proteins, PTPN14 was highly likely a novel sperm-motility biomarker and a potential mitochondrial protein.

Melatonin reduces pancreatic tumor cell viability by altering mitochondrial physiology

Melatonin reduces proliferation in many different cancer cell lines. Thus, melatonin is considered a promising antitumor agent, promoting apoptosis in tumor cells while preserving viability of normal cells. Herein, we examined the effects of melatonin on the pancreatic AR42J tumor cell line. We have analyzed cytosolic-free Ca(2+) concentration ([Ca(2+) ](c) ), mitochondrial-free Ca(2+) concentration ([Ca(2+) ](m) ), mitochondrial membrane potential (Ψm), mitochondrial flavin adenine dinucleotide (FAD) oxidative state, cellular viability and caspase-3 activity. Our results show that melatonin induced transient changes in [Ca(2+) ](c) and [Ca(2+) ](m) . Melatonin also induced depolarization of Ψm and led to a reduction in the level of oxidized FAD. In addition, melatonin reduced AR42J cell viability. Finally, we found a Ca(2+) -dependent caspase-3 activation in response to melatonin. Collectively, these data support the likelihood that melatonin reduces viability of tumor AR42J cells via its action on mitochondrial activity and caspase-3 activation.

Relationship of protein tyrosine phosphorylation state with tolerance to frozen storage and the potential to undergo cyclic AMP-dependent hyperactivation in the spermatozoa of Japanese Black bulls

The aim of this study was to elucidate the relationship between protein tyrosine phosphorylation state and sperm characteristics in frozen-stored spermatozoa of Japanese Black bulls. The spermatozoa were washed with PBS containing polyvinyl alcohol and then incubated with cell-permeable cAMP analog cBiMPS to induce flagellar hyperactivation. Before and after incubation, the spermatozoa were used for immunodetection of tyrosine-phosphorylated proteins, assessment of morphological acrosome condition and evaluation of motility. In bulls whose frozen-stored spermatozoa were classified as having a high-grade acrosome condition before incubation, sperm tyrosine-phosphorylated proteins, including the 33-kDa tyrosine-phosphorylated SPACA1 protein, were localized in the anterior region of the acrosome and equatorial subsegment. The immunodetection level of the 41- and 33-kDa sperm tyrosine-phosphorylated proteins in the Western blots and the immunofluorescence of tyrosine-phosphorylated proteins and SPACA1 proteins in the anterior region of the sperm acrosome were lower in bulls whose frozen-stored sperm were classified as having a low-grade acrosome condition. On the other hand, after incubation with cBiMPS, immunodetection levels of at least 10 tyrosine-phosphorylated proteins increased in the connecting and principal pieces of spermatozoa, coincident with the induction of flagellar hyperactivation. Many of the spermatozoa also exhibited detection patterns similar to those of boar hyperactivated spermatozoa. These results are consistent with the suggestion that immunodetection levels of tyrosine-phosphorylated proteins are valid markers that can predict the level of tolerance to frozen storage and the potential to undergo cAMP-dependent hyperactivation for the spermatozoa of individual Japanese Black bulls.

Protein phosphatase 1 complexes modulate sperm motility and present novel targets for male infertility

Infertility is a growing concern in modern society, with 30% of cases being due to male factors, namely reduced sperm concentration, decreased motility and abnormal morphology. Sperm cells are highly compartmentalized, almost devoid of transcription and translation consequently processes such as protein phosphorylation provide a key general mechanism for regulating vital cellular functions, more so than for undifferentiated cells. Reversible protein phosphorylation is the principal mechanism regulating most physiological processes in eukaryotic cells. To date, hundreds of protein kinases have been identified, but significantly fewer phosphatases (PPs) are responsible for counteracting their action. This discrepancy can be explained in part by the mechanism used to control phosphatase activity, which is based on regulatory interacting proteins. This is particularly true for PP1, a major serine/threonine-PP, for which >200 interactors (PP1 interacting proteins-PIPs) have been indentified that control its activity, subcellular location and substrate specificity. For PP1, several isoforms have been described, among them PP1γ2, a testis/sperm-enriched PP1 isoform. Recent findings support our hypothesis that PP1γ2 is involved in the regulation of sperm motility. This review summarizes the known sperm-specific PP1-PIPs, involved in the acquisition of mammalian sperm motility. The complexes that PP1 routinely forms with different proteins are addressed and the role of PP1/A-kinase anchoring protein complexes in sperm motility is considered. Furthermore, the potential relevance of targeting PP1-PIPs complexes to infertility diagnostics and therapeutics as well as to male contraception is also discussed.