Role of tyrosine phosphorylation in sperm capacitation / acrosome reaction

A Review: Biomechanical Aspects of the Fallopian Tube Relevant to its Function in Fertility

The fallopian tube (FT) plays a crucial role in the reproductive process by providing an ideal biomechanical and biochemical environment for fertilization and early embryo development. Despite its importance, the biomechanical functions of the FT that originate from its morphological aspects, and ultrastructural aspects, as well as the mechanical properties of FT, have not been studied nor used sufficiently, which limits the understanding of fertilization, mechanotrasduction, and mechanobiology during embryo development, as well as the replication of the FT in laboratory settings for infertility treatments. This paper reviews and revives valuable information on human FT reported in medical literature in the past five decades relevant to the biomechanical aspects of FT. In this review, we summarized the current state of knowledge concerning the morphological, ultrastructural aspects, and mechanical properties of the human FT. We also investigate the potential arising from a thorough consideration of the biomechanical functions and exploring often neglected mechanical aspects. Our investigation encompasses both macroscopic measurements (such as length, diameter, and thickness) and microscopic measurements (including the height of epithelial cells, the percentage of ciliated cells, cilia structure, and ciliary beat frequency). Our primary focus has been on healthy women of reproductive age. We have examined various measurement techniques, encompassing conventional metrology, 2D histological data as well as new spatial measurement techniques such as micro-CT.

Effect of exogenous sperm capacitation inducers on stallion sperm

Although under appropriate laboratory conditions, sperm from different mammalian species can be capacitated in vitro, the optimal conditions for sperm capacitation in the stallion have been elusive. This study evaluated the effect of different capacitating inducers in Whitten and Tyrode media and assessed their impact on capacitation-related factors. Stallion sperm were incubated with different combinations of capacitating inducers at 38.5 °C in an air atmosphere. Sperm quality variables such as motility, mitochondrial membrane potential, and lipid peroxidation were assessed. Membrane fluidity and intracellular calcium levels were evaluated as early markers of capacitation, while tyrosine phosphorylation events and the sperm's ability to perform acrosomal exocytosis were used as late capacitation markers. Finally, these sperm were evaluated using a heterologous zona pellucida binding assay. The findings confirm that capacitating conditions evaluated increase intracellular calcium levels and membrane fluidity in both media. Similarly, including 2 or 3 inducers in both media increased tyrosine phosphorylation levels and acrosomal exocytosis after exposure to progesterone, confirming that stallion sperm incubated in these conditions shows cellular and molecular changes consistent with sperm capacitation. Furthermore, the zona pellucida binding assay confirmed the binding capacity of sperm incubated in capacitation conditions, a key step for stallion in vitro fertilization success. Further studies are needed to evaluate the effect of these conditions on in vitro fertilization in the horse.

Global proteomic analyses of lysine acetylation, malonylation, succinylation, and crotonylation in human sperm reveal their involvement in male fertility

Protein lysine modifications (PLMs) are hotspots of post-translational modifications and are involved in many diseases; however, their role in human sperm remains obscure. This study examined the presence and functional roles of a classical PLM (lysine acetylation, Kac) and three novel PLMs (lysine malonylation, Kmal; lysine succinylation, Ksucc; lysine crotonylation, Kcr) in human sperm. Immunoblotting and immunofluorescence assays revealed modified proteins (15-150 kDa) in the tails of human sperm. An immunoaffinity approach coupled with liquid chromatography/tandem mass spectrometry revealed 1423 Kac sites in 680 proteins, 196 Kmal sites in 118 proteins, 788 Ksucc sites in 251 proteins, and 1836 Kcr sites in 645 proteins. These modified proteins participate in a variety of biological processes and metabolic pathways. Crosstalk analysis demonstrated that proteins involved in the sperm energy pathways of glycolysis, oxidative phosphorylation, the citrate cycle, fatty acid oxidation, and ketone body metabolism were modified by at least one of these modifications. In addition, these modifications were found in 62 male fertility-related proteins that weave a protein-protein interaction network associated with asthenoteratozoospermia, asthenozoospermia, globozoospermia, spermatogenic failure, hypogonadotropic hypogonadism, and polycystic kidney disease. Our findings shed light on the functional role of PLMs in male reproduction. SIGNIFICANCE: Protein lysine modifications (PLMs) are hotspots of posttranslational modifications and are involved in many diseases. This study revealed the presence of a classical PLM (lysine acetylation) and three novel PLMs (lysine malonylation, lysine succinylation, and lysine crotonylation) in human sperm tails. The modified proteins participate in a variety of biological processes and metabolic pathways. In addition, these modifications were found in 62 male infertility-associated proteins and could serve as potential diagnostic markers and therapeutic targets for male infertility.

Nirmatrelvir has detrimental effects on sperm function by altering the PI3K/PDK1/AKT signaling pathway

Nirmatrelvir (NMV) is a recently developed selective inhibitor of the main protease of Sars-Cov-2 that reduces the severity of infection. Despite its widespread use and various side effects, NMV's effect on male fertility is still unclear. This study was thus established to investigate how NMV affects male fertility. For experiments, Duroc spermatozoa were incubated with various concentrations of NMV (0, 0.1, 1, 10, 50, and 100 μM). Then, sperm motility, motion kinematics, capacitation status, intracellular ATP level, and cell viability were evaluated. In addition, the expression levels of phospho-PKA substrates, tyrosine-phosphorylated proteins, and PI3K/PDK1/AKT signaling pathway-related proteins were measured by western blotting. Our results showed that sperm motility, motion kinematics, proportion of capacitated spermatozoa, and intracellular ATP level were significantly decreased by NMV in a dose-dependent manner. Moreover, PKA activation was significantly suppressed by NMV, and expression levels of PI3K, phospho-PDK1, AKT, and phospho-AKT (Thr308 and Ser473) were significantly increased in a dose-dependent manner. Combining these findings, it is suggested that NMV has detrimental effects on sperm function by inducing abnormal changes in the PI3K/PDK1/AKT signaling pathway, resulting in PKA deactivation. Therefore, there is a need to pay particular attention to its male reproductive toxicity when NMV is administered.

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

Adverse Effects of Avobenzone on Boar Sperm Function: Disruption of Protein Kinase A Activity and Tyrosine Phosphorylation

Avobenzone (AVO), an ultraviolet (UV) filter, is frequently used as an ingredient in personal cosmetics. This UV filter has been found to be easily exposed in swimming pools and beaches, and it has been detected in human urine and blood. Moreover, numerous studies have demonstrated that AVO exhibits endocrine-disrupting properties. Nevertheless, the effects of AVO on male fertility have not yet fully understood. Therefore, this study aimed to assess the effects of AVO on various sperm functions during capacitation. First, boar spermatozoa were treated with various AVO concentrations. After treatment, sperm motility and kinetic characteristics, capacitation status, intracellular adenosine triphosphate (ATP) levels, and sperm viability were evaluated. Moreover, Western blot analysis w.as conducted to evaluate protein kinase A (PKA) activity and tyrosine phosphorylation. As a result, AVO treatment significantly decreased total motility, progressive motility, and several kinetic characteristics at high concentrations (50 and 100 μM). Furthermore, the capacitation status dose-dependently decreased. Conversely, no significant differences in acrosome reaction, cell viability, and intracellular ATP levels were observed. However, the intracellular ATP level tended to decrease. In addition, AVO dose-dependently induced abnormal changes in PKA activity and tyrosine phosphorylation. Although AVO did not directly exert a toxic effect on cell viability, it ultimately negatively affected sperm functions through abnormal alterations in PKA activity and tyrosine phosphorylation. Thus, the potential implications on male fertility must be considered when contemplating the safe utilization of AVO.

Clinical use of progesterone in human sperm preparation media for increasing IVF success

RESEARCH QUESTION

Can the addition of progesterone and neurotensin, molecular agents found in the female reproductive tract, after sperm washing increase the fertilization potential of human spermatozoa?

DESIGN

(i) Cohort study of 24 men. Spermatozoa selected by swim-up were incubated in either progesterone or neurotensin (0.1-100 µM) for 1-4 h, and hyperactive motility and binding to hyaluronan (0.1-100 µM) were assessed. The effect of progesterone 10 µM on sperm function was assessed in a blinded manner, including: hyperactive motility, binding to hyaluronan, tyrosine phosphorylation, acrosome reaction and oxidative DNA damage. (i) Embryo safety testing [one-cell mouse embryo assay (MEA), endotoxin and sterility counts (n = 3)] in preclinical embryo models of IVF (murine and porcine, n = 7 each model) and a small preliminary human study (n = 4) of couples undergoing standard IVF with oocytes inseminated with spermatozoa ± 10 µM progesterone.

RESULTS

Progesterone 10 µM increased sperm binding to hyaluronan, hyperactive motility and tyrosine phosphorylation (all P < 0.05). Neurotensin had no effect (P > 0.05). Progesterone 10 µM in human embryo culture media passed embryo safety testing (MEA, endotoxin concentration and sterility plate count). In preclinical models of IVF, the exposure of spermatozoa to progesterone 10 µM and oocytes to progesterone 1 µM was not detrimental, and increased the fertilization rate in mice and the blastocyst cell number in mice and pigs (all P ≤ 0.03). In humans, every transferred blastocyst that had been produced from spermatozoa exposed to progesterone resulted in a live birth.

CONCLUSION

The addition of progesterone to sperm preparation media shows promise as an adjunct to current methods for increasing fertilization potential. Randomized controlled trials are required to determine the clinical utility of progesterone for improving IVF outcomes.

From TgO/GABA-AT, GABA, and T-263 Mutant to Conception of Toxoplasma

Toxoplasma gondii causes morbidity, mortality, and disseminates widely via cat sexual stages. Here, we find T. gondii ornithine aminotransferase (OAT) is conserved across phyla. We solve TgO/GABA-AT structures with bound inactivators at 1.55 Å and identify an inactivator selective for TgO/GABA-AT over human OAT and GABA-AT. However, abrogating TgO/GABA-AT genetically does not diminish replication, virulence, cyst-formation, or eliminate cat's oocyst shedding. Increased sporozoite/merozoite TgO/GABA-AT expression led to our study of a mutagenized clone with oocyst formation blocked, arresting after forming male and female gametes, with "Rosetta stone"-like mutations in genes expressed in merozoites. Mutations are similar to those in organisms from plants to mammals, causing defects in conception and zygote formation, affecting merozoite capacitation, pH/ionicity/sodium-GABA concentrations, drawing attention to cyclic AMP/PKA, and genes enhancing energy or substrate formation in TgO/GABA-AT-related-pathways. These candidates potentially influence merozoite's capacity to make gametes that fuse to become zygotes, thereby contaminating environments and causing disease.

Prevention of seminal vesicle damage by Mucuna pruriens var. pruriens seed extract in chronic unpredictable mild stress mice

CONTEXT

Thai Mucuna pruriens (L.) DC. var. pruriens (Fabaceae) or T-MP seed extract has been shown to improve sexual performance and sperm quality.

OBJECTIVE

This study investigates the preventive effects of T-MP against seminal vesicle damage, apoptotic and Nrf2 protein expression in mice under chronic unpredictable mild stress (CUMS).

MATERIALS AND METHODS

Forty-eight male ICR mice were divided into four groups: control, CUMS, T-MP300 + CUMS and T-MP600 + CUMS. Mice in control and CUMS groups received distilled water, while those in treated groups were pretreated with T-MP extract (300 or 600 mg/kg BW) for 14 consecutive days. The CMUS and co-treated groups were exposed to one random stressor (of 12 total) each day for 43 days. Components and histopathology of the seminal vesicle were examined, along with localization of androgen receptor (AR) and caspase 3. Expression of seminal AR, tyrosine phosphorylated (TyrPho), heat shock protein 70 (Hsp70), caspases (3 and 9) and nuclear factor erythroid 2-related factor 2 (Nrf2) proteins was investigated.

RESULTS

T-MP extract at a dose of 600 mg/kg BW improved seminal epithelial damage and secretion of fluid containing essential substances and proteins in CUMS mice. It also increased the expression of AR and TyrPho proteins. Additionally, T-MP increased expression of Nrf2 and inhibited seminal vesicular apoptosis through the suppression of Hsp70 and caspase expression.

CONCLUSION

T-MP seeds have an antiapoptotic property in chronic stress seminal vesicle. It is possible to apply this extract for the enhancement of seminal plasma quality.

The Cation/Calcium Channel of Sperm (CatSper): A Common Role Played Despite Inter-Species Variation?

The main cation/calcium channel of spermatozoa (CatSper), first identified in 2001, has been thoroughly studied to elucidate its composition and function, while its distribution among species and sperm sources is yet incomplete. CatSper is composed of several subunits that build a pore-forming calcium channel, mainly activated in vivo in ejaculated sperm cells by intracellular alkalinization and progesterone, as suggested by the in vitro examinations. The CatSper channel relevance is dual: to maintain sperm homeostasis (alongside the plethora of membrane channels present) as well as being involved in pre-fertilization events, such as sperm capacitation, hyperactivation of sperm motility and the acrosome reaction, with remarkable species differences. Interestingly, the observed variations in CatSper localization in the plasma membrane seem to depend on the source of the sperm cells explored (i.e., epididymal or ejaculated, immature or mature, processed or not), the method used for examination and, particularly, on the specificity of the antibodies employed. In addition, despite multiple findings showing the relevance of CatSper in fertilization, few studies have studied CatSper as a biomarker to fine-tune diagnosis of sub-fertility in livestock or even consider its potential to control fertilization in plague animals, a more ethically defensible strategy than implicating CatSper to pharmacologically modify male-related fertility control in humans, pets or wild animals. This review describes inter- and intra-species differences in the localization, structure and function of the CatSper channel, calling for caution when considering its potential manipulation for fertility control or improvement.

The natural flavonoid compound deguelin suppresses sperm (Sus Scrofa) functions through abnormal activation of the PI3K/AKT pathway

Deguelin is a natural flavonoid extracted from plants belonging to the Lonchocarpus, Derris, or Tephrosia genera. It inhibits AKT activity in tumors and has the potential to be used as a treatment for malignant tumors. However, the risks associated with the use of deguelin on male fertility have not yet been explained in detail. Therefore, this study was conducted to investigate the effects of deguelin on sperm functions during capacitation. First, boar spermatozoa were exposed to different concentrations of deguelin (0.1, 1, 10, 50, and 100 μM). Next, sperm functional assessments, such as sperm motility, capacitation status, intracellular ATP level, and cell viability, were performed. The expression levels of PI3K/AKT-related proteins and the phosphorylation of their tyrosine residues were also evaluated by western blotting. No significant difference was observed in cell viability; however, deguelin considerably decreased sperm motility and motion kinematics in a dose-dependent manner. Although no significant difference was observed in the capacitation status, acrosome reaction decreased at high concentrations of deguelin (50 and 100 μM). Furthermore, intracellular ATP levels were significantly decreased in all deguelin treatment groups compared with those in the control group. Results of western blotting revealed that deguelin substantially diminished tyrosine phosphorylation. Interestingly, in contrast to previous studies showing that deguelin inhibits AKT activity, our results showed that it increased the expression of PI3K/AKT pathway-related proteins. Collectively, these findings indicate that deguelin exerts negative effects on sperm functions due to abnormal PI3K/AKT signaling activation. We believe that this is the first study to provide evidence that deguelin can regulate sperm functions independent of PI3K/AKT pathway inhibition. Furthermore, its detrimental effects on male fertility should be considered while developing or using deguelin as a therapeutic agent.

Understanding the impact of varicocele on sperm capacitation

OBJECTIVE

To study the relationship between the seminal sample quality of men with varicocele and sperm capacitation.

DESIGN

Cross-sectional observational study.

SETTING

Academic hospital.

PATIENT(S)

Seventy-six men (19 control and 57 with varicocele) were analyzed.

INTERVENTION(S)

Semen samples were submitted to a discontinuous density gradient for sperm selection. Sperm capacitation was induced using a human tubal fluid medium supplemented with bovine serum albumin.

MAIN OUTCOME MEASURE(S)

After capacitation induction, the sperm were assessed by capacitation state, computer-assisted sperm motility, mitochondrial activity, membrane integrity, acrosome reaction, and intracellular oxidative stress.

RESULT(S)

The capacitation period increased sperm motility, showing an increase in the average path velocity and a decrease in the straightness compared with sperm before capacitation (paired analysis). After capacitation, the rate of capacitated sperm, motility, and mitochondrial activity showed differences between groups (control and varicocele). The varicocele group showed lower mitochondrial activity and capacitation than the control group. On the other hand, no significant differences were observed in the other variables evaluated.

CONCLUSION(S)

Varicocele men showed less viable sperm and mitochondrial activity than control men after capacitation sperm. The induction of capacitation altered motility by increasing path velocity and decreasing straightness in all of the studied groups, evidencing the occurrence of hyperactivation.

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.

Structures of sperm flagellar doublet microtubules expand the genetic spectrum of male infertility

Sperm motility is crucial for successful fertilization. Highly decorated doublet microtubules (DMTs) form the sperm tail skeleton, which propels the movement of spermatozoa. Using cryo-electron microscopy (cryo-EM) and artificial intelligence (AI)-based modeling, we determined the structures of mouse and human sperm DMTs and built an atomic model of the 48-nm repeat of the mouse sperm DMT. Our analysis revealed 47 DMT-associated proteins, including 45 microtubule inner proteins (MIPs). We identified 10 sperm-specific MIPs, including seven classes of Tektin5 in the lumen of the A tubule and FAM166 family members that bind the intra-tubulin interfaces. Interestingly, the human sperm DMT lacks some MIPs compared with the mouse sperm DMT. We also discovered variants in 10 distinct MIPs associated with a subtype of asthenozoospermia characterized by impaired sperm motility without evident morphological abnormalities. Our study highlights the conservation and tissue/species specificity of DMTs and expands the genetic spectrum of male infertility.

Molecular Chaperone HSPA2 Distribution During Hyaluronic Acid Selection in Human Sperm

During fertilization, sperm hyaluronidase activity is essential for spermatozoa to successfully penetrate the hyaluronic acid-enriched extracellular matrix of the cumulus cells. Since molecular chaperones, as the heat shock protein A2, are typically involved in bringing hyaluronic acid receptors to the cell surface, here we evaluated the presence and spatial location of HSPA2 on human spermatozoa based on its hyaluronic acid binding capacity. This study included 16 normozoospermic sperm samples from volunteering donors. The location of HSPA2 was studied in cells before and after 1-h incubation under capacitating conditions, as well as in spermatozoa selected according to their ability of binding to hyaluronic acid. Our results showed no significant differences in HSPA2 immunofluorescent cells before and after 1 h of incubation in capacitating conditions. Nevertheless, after hyaluronic acid selection, the percentage of HSPA2-labelled cells increased significantly, indicating that the interaction with hyaluronic acid may induce the unmasking of HSPA2 epitopes. Furthermore, after swim-up and hyaluronic acid selection, spermatozoa presented a highly immunostained equatorial band with a homogeneous fluorescence throughout the acrosomal region. This distribution has been previously suggested to have important implications in male fertility. Noteworthy, a homogeneous fluorescence among the acrosomal region with a more intense labelling at the apical region was observed only in hyaluronic acid bound sperm cells, which may be associated with primary gamete recognition. Our findings suggest that the hyaluronic acid selection technique and HSPA2 biomarker should be considered candidates to complement the classic seminal analysis before recommending an appropriate assisted reproduction technique.

Proper phosphorylation of septin 12 regulates septin 4 and soluble adenylyl cyclase expression to induce sperm capacitation

Septin-based ring complexes maintain the sperm annulus. Defective annular structures are observed in the sperm of Sept12- and Sept4-null mice. In addition, sperm capacitation, a process required for proper fertilization, is inhibited in Sept4-null mice, implying that the sperm annulus might play a role in controlling sperm capacitation. Hence, we analyzed sperm capacitation of sperm obtained from SEPT12 Ser196 phosphomimetic (S196E), phosphorylation-deficient (S196A), and SEPT4-depleted mutant mice. Capacitation was reduced in the sperm of both the Sept12 S196E- and Sept12 S196A-knock-in mice. The protein levels of septins, namely, SEPT4 and SEPT12, were upregulated, and these proteins were concentrated in the sperm annulus during capacitation. Importantly, the expression of soluble adenylyl cyclase (sAC), a key enzyme that initiates capacitation, was upregulated, and sAC was recruited to the sperm annulus following capacitation stimulation. We further found that SEPT12, SEPT4, and sAC formed a complex and colocalized to the sperm annulus. Additionally, sAC expression was reduced and disappeared in the annulus of the SEPT12 S196E- and S196A-mutant mouse sperm. In the sperm of the SEPT4-knockout mice, sAC did not localize to the annulus. Thus, our data demonstrate that SEPT12 phosphorylation status and SEPT4 activity jointly regulate sAC protein levels and annular localization to induce sperm capacitation.

Extracellular vesicles-encapsulated microRNA in mammalian reproduction: A review

Extracellular vesicles (EVs) are nanoscale cell-derived lipid vesicles that participate in cell-cell communication by delivering cargo, including mRNAs, proteins and non-coding RNAs, to recipient cells. MicroRNA (miRNA), a non-coding RNA typically 22 nucleotides long, is crucial for nearly all developmental and pathophysiological processes in mammals by regulating recipient cells gene expression. Infertility is a worldwide health issue that affects 10-15% of couples during their reproductive years. Although assisted reproductive technology (ART) gives infertility couples hope, the failure of ART is mainly unknown. It is well accepted that EVs-encapsulated miRNAs have a role in different reproductive processes, implying that these EVs-encapsulated miRNAs could optimize ART, improve reproductive rate, and treat infertility. As a result, in this review, we describe the present understanding of EVs-encapsulated miRNAs in reproduction regulation.

Influence of Two Widely Used Solvents, Ethanol and Dimethyl Sulfoxide, on Human Sperm Parameters

To study mechanisms involved in fertility, many experimental assays are conducted by incubating spermatozoa in the presence of molecules dissolved in solvents such as ethanol (EtOH) or dimethyl sulfoxide (DMSO). Although a vehicle control group is usually included in such studies, it does not allow to evaluate the intrinsic effect of the solvent on sperm parameters and its potential influence on the outcome of the experiment. In the present study, we incubated human spermatozoa for 4 h in a capacitation medium in the absence or the presence of different concentrations of EtOH and DMSO (0.1, 0.5, 1.0, and 2.0%) to assess the impact of these solvents on sperm motility, vitality, capacitation, and acrosome integrity. The presence of statistically significant relationships between increasing solvent concentrations and the investigated parameters was assessed using linear mixed models. A significant effect was observed with both solvents for total and progressive sperm motilities. We also evaluated the effect of time for these parameters and showed that the influence of the solvents was stable between 0 and 4 h, indicating an almost direct impact of the solvents. While EtOH did not influence sperm vitality and acrosome integrity, a significant effect of increasing DMSO concentrations was observed for these parameters. Finally, regarding capacitation, measured via phosphotyrosine content, although a dose-dependent effect was observed with both solvents, the statistical analysis did not allow to precisely evaluate the intensity of the effect. Based on the results obtained in the present study, and the corresponding linear mixed models, we calculated the concentration of both solvents which would result in a 5% decline in sperm parameters. For EtOH, these concentrations are 0.9, 0.7, and 0.3% for total motility, progressive motility, and capacitation, respectively, while for DMSO they are 1.5, 1.1, >2, 0.3 and >2% for total motility, progressive motility, vitality, capacitation, and acrosome integrity, respectively. We recommend using solvent concentrations below these values to dissolve molecules used to study sperm function in vitro, to limit side effects.

Dolichandrone serrulata flower improves seminal biochemical parameters and proteins in T2DM rats induced by a high-fat diet and streptozotocin

CONTEXT

Although Dolichandrone serrulata (Wall. ex DC.) Seem (Bignoniaceae) flower (DSF) improves hyperglycaemia, testicular damage and sperm quality in type 2 diabetes mellitus (T2DM) animals, its effects on the seminal vesicles, secreting seminal plasma, are unknown.

OBJECTIVE

This study reports the protective effects of DSF on seminal dysfunction in T2DM rats.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into four groups (control, T2DM, T2DM + DSF200 and T2DM + DSF600; 10 animals/group). The control group was fed a low-fat diet for 14 days prior to single saline injection, whereas T2DM group was given a high-fat diet and injected with streptozocin (50 mg/kg body weight). The T2DM-induced rats were fed DSF orogastrically (200 and 600 mg/kg body weight) for 28 consecutive days. At the end of the experiment, biochemical components, malondialdehyde (MDA), histology and protein expression in seminal lysate were evaluated.

RESULTS

DSF increased the levels of serum phosphorus (13.66 ± 0.59 mg/dL), ALP (11.85 ± 0.99 U/L), GOT (3938.23 ± 251.41 U/L) and GPT (34.16 ± 4.93), decreased MDA levels in seminal tissue, and elevated the serum testosterone in the T2DM rats. Treatment with DSF ameliorated histological damage, significantly increased seminal 44 and 31 kDa TyrPho protein expression, and decreased that of caspase 3 and 9.

CONCLUSIONS

DSF extract was able to mitigate seminal dysfunction in T2DM rats via improvements of tyrosine phosphorylation, testosterone level and biochemical substances, as well as reductions of caspase proteins. DSF may be developed as an alternative medicine in treating of T2DM male subfertility and progressive complications.

Reproductive Toxicity of Ritonavir in Male: insight into mouse sperm capacitation

Since COVID-19 began in 2019, therapeutic agents are being developed for its treatment. Among the numerous potential therapeutic agents, ritonavir (RTV), an anti-viral agent, has recently been identified as an important element of the COVID-19 treatment. Moreover, RTV has also been applied in the drug repurposing of cancer cells. However, previous studies have shown that RTV has toxic effects on various cell types. In addition, RTV regulates AKT phosphorylation within cancer cells, and AKT is known to control sperm functions (motility, capacitation, and so on). Although deleterious effects of RTV have been reported, it is not known whether RTV has male reproduction toxicity. Therefore, in this study, we aimed to investigate the effects of RTV on sperm function and male fertility. In the present study, sperm collected from the cauda epididymis of mice were incubated with various concentrations of RTV (0, 0.1, 1, 10, and 100 μM). The expression levels of AKT, phospho-AKT (Thr³⁰⁸ and Ser⁴⁷³), and phospho-tyrosine proteins, sperm motility, motion kinematics, capacitation status, and cell viability were assessed after capacitation. The results revealed that AKT phosphorylation at Thr³⁰⁸ and Ser⁴⁷³ was significantly increased, and the levels of tyrosine-phosphorylated proteins (at approximately 25 and 100 kDa) were significantly increased in a dose-dependent manner. In addition, RTV adversely affected sperm motility, motion kinematics, and cell viability. Taken together, RTV may have negative effects on sperm function through an abnormal increase in tyrosine phosphorylation and phospho-AKT levels. Therefore, individuals taking or prescribing RTV should be aware of its reproductive toxicity.

Extracellular vesicle-encapsulated miR-21-5p in seminal plasma prevents sperm capacitation via Vinculin inhibition

To penetrate the zona pellucida before sperm-egg binding, sperm must undergo highly time-controlled capacitation and acrosome reaction in the female reproductive tract. Our previous study demonstrated that miR-21-5p is the most abundant miRNA in boar seminal plasma (SP)-derived extracellular vesicles (EVs) and can target Vinculin (VCL) gene, which may participate in boar sperm capacitation. Thus, this study aims to explore the potential role of miR-21-5p from SP-derived EVs in preventing sperm capacitation and its underlying mechanism. We observed that sperm could incorporate miR-21-5p from SP-derived EVs. The roles of SP-derived EVs miR-21-5p in sperm capacitation were then determined using gain- and loss-of-function analyses. In addition, the expression levels of miR-21-5p, VCL, and VCL protein in liquid-preserved boar sperm following transfection were determined using RT-qPCR and Western blotting. Our results revealed that miR-21-5p overexpression inhibited sperm capacitation and acrosome reaction. Similarly, miR-21-5p expression was significantly lower (P < 0.05) in capacitated sperm than un-capacitated sperm. However, the protein level of VCL was also significantly lower (P < 0.05) in capacitated sperm than un-capacitated sperm. Furthermore, immunofluorescence analysis showed that VCL protein mainly located in sperm head and sperm capacitation was inhibited after treating with VCL protein inhibitor (Chrysin). In conclusion, our study provides reasonable evidence that miR-21-5p expression in SP-derived EVs could prevent sperm capacitation via VCL inhibition.

The ribosome inhibitor chloramphenicol induces motility deficits in human spermatozoa: A proteomic approach identifies potentially involved proteins

Mature spermatozoa are almost completely devoid of cytoplasm; as such it has long been believed that they do not contain ribosomes and are therefore not capable of synthesising proteins. However, since the 1950s, various studies have shown translational activity within spermatozoa, particularly during their in vitro capacitation. But the type of ribosomes involved (cytoplasmic or mitochondrial) is still debated. Here, we investigate the presence and activity of the two types of ribosomes in mature human spermatozoa. By targeting ribosomal RNAs and proteins, we show that both types of ribosomes are localized in the midpiece as well as in the neck and the base of the head of the spermatozoa. We assessed the impact of cycloheximide (CHX) and chloramphenicol (CP), inhibitors of cytoplasmic and mitochondrial ribosomes, respectively, on different sperm parameters. Neither CHX, nor CP impacted sperm vitality, mitochondrial activity (measured through the ATP content), or capacitation (measured through the content in phosphotyrosines). However, increasing CP concentrations induced a decrease in total and progressive motilities as well as on some kinematic parameters while no effect was observed with CHX. A quantitative proteomic analysis was performed by mass spectrometry in SWATH mode to compare the proteomes of spermatozoa capacitated in the absence or presence of the two ribosome inhibitors. Among the ∼700 proteins identified in the different tested conditions, 3, 3 and 25 proteins presented a modified abundance in the presence of 1 and 2 mg/ml of CHX, and 1 mg/ml of CP, respectively. The observed abundance variations of some CP-down regulated proteins were validated using Multiple-Reaction Monitoring (MRM). Taken together, our results are in favor of an activity of mitochondrial ribosomes. Their inhibition by CP results in a decrease in the abundance of several proteins, at least FUNDC2 and QRICH2, and consequently induces sperm motility deficits.

Unbalanced Expression of Glutathione Peroxidase 4 and Arachidonate 15-Lipoxygenase Affects Acrosome Reaction and In Vitro Fertilization

Glutathione peroxidase 4 (Gpx4) and arachidonic acid 15 lipoxygenase (Alox15) are counterplayers in oxidative lipid metabolism and both enzymes have been implicated in spermatogenesis. However, the roles of the two proteins in acrosomal exocytosis have not been explored in detail. Here we characterized Gpx4 distribution in mouse sperm and detected the enzyme not only in the midpiece of the resting sperm but also at the anterior region of the head, where the acrosome is localized. During sperm capacitation, Gpx4 translocated to the post-acrosomal compartment. Sperm from Gpx4^+/Sec46Ala mice heterozygously expressing a catalytically silent enzyme displayed an increased expression of phosphotyrosyl proteins, impaired acrosomal exocytosis after in vitro capacitation and were not suitable for in vitro fertilization. Alox15-deficient sperm showed normal acrosome reactions but when crossed into a Gpx4-deficient background spontaneous acrosomal exocytosis was observed during capacitation and these cells were even less suitable for in vitro fertilization. Taken together, our data indicate that heterozygous expression of a catalytically silent Gpx4 variant impairs acrosomal exocytosis and in vitro fertilization. Alox15 deficiency hardly impacted the acrosome reaction but when crossed into the Gpx4-deficient background spontaneous acrosomal exocytosis was induced. The detailed molecular mechanisms for the observed effects may be related to the compromised redox homeostasis.

Carboxypeptidase E protein regulates porcine sperm Ca2+ influx to affect capacitation and fertilization

Mammalian spermatozoa acquire their fertilizing ability in the epididymis, which is important for sperm maturation and capacitation. Carboxypeptidase E (CPE) is a prohormone-processing enzyme and sorting receptor that functions intracellularly. Recently, CPE was identified to exist in the seminal plasma. However, little is known about the effects of CPE on reproductive function. This study focused on the effects of CPE on sperm function and fertilization. Herein, CPE was identified to be localized in the boar sperm, testis, epididymis, accessory gonad and seminal plasma, with high expression found in the bulbourethral glands and cauda epididymis. Furthermore, compared with high motility spermatozoa, a decrease in CPE abundance was observed in low motile spermatozoa by Western blot analysis. The use of specific antibody to inhibit the CPE in spermatozoa led to a decrease in sperm motility, followed by an expected decrease in acrosome exocytosis and tyrosine phosphorylation in the capacitation process. These changes were accompanied by a decrease in intracellular Ca²⁺ ([Ca²⁺]_i) influx, which resulted in a significant decrease in the cleavage rate during in vitro fertilization (IVF). Based on these observations, we suggest that CPE might affect porcine sperm Ca²⁺ influx to participate in the regulation of sperm function during capacitation.

Recombinant human OVGP1 increases intracellular calcium and further potentiates the effects of progesterone on human sperm

Purpose

To investigate the effects of recombinant human oviduct–specific glycoprotein (rHuOVGP1) alone and in combination with progesterone (P4) on intracellular Ca²⁺ concentration [Ca²⁺]_i and to investigate if rHuOVGP1 in combination with P4 can further enhance tyrosine phosphorylation (pY) of sperm proteins during human sperm capacitation.

Methods

Fluorometric flow cytometry was performed to examine the effects of rHuOVGP1 on [Ca²⁺]_i in human sperm during capacitation. Confocal microscopy was used in conjunction with live cell imaging to analyze the influence of rHuOVGP1 and P4 on [Ca²⁺]_i in the sperm tail and to examine the involvement of CatSper channels in their effect on [Ca²⁺]_i. Western blot analysis was performed to assess the protein levels of p105, a major tyrosine-phosphorylated sperm protein.

Results

rHuOVGP1 increases [Ca²⁺]_i in human sperm at the beginning of capacitation and further increases and sustains the level of [Ca²⁺]_i in the sperm tail following the addition of P4. Inhibition of CatSper channels impedes the effects of rHuOVGP1 on [Ca²⁺]_i in the sperm tail. P4 alone can increase pY of a major human sperm protein, p105, yet yields a further increase when used in combination with rHuOVGP1.

Conclusion

The present study revealed that rHuOVGP1 may work with P4 to upregulate [Ca²⁺]_i at the beginning of capacitation in part through CatSper channels which, in turn, leads to the downstream event of pY of sperm proteins and enhancement of sperm capacitation.

Supplementary information

The online version contains supplementary material available at 10.1007/s10815-022-02591-0.

Targeted Analysis of HSP70 Isoforms in Human Spermatozoa in the Context of Capacitation and Motility

HSP70s constitute a family of chaperones, some isoforms of which appear to play a role in sperm function. Notably, global proteomic studies analyzing proteins deregulated in asthenozoospermia, a main cause of male infertility characterized by low sperm motility, showed the dysregulation of some HSP70 isoforms. However, to date, no clear trend has been established since the variations in the abundance of HSP70 isoforms differed between studies. The HSPA2 isoform has been reported to play a key role in fertilization, but its dysregulation and possible relocation during capacitation, a maturation process making the spermatozoon capable of fertilizing an oocyte, is debated in the literature. The aim of the present study was to investigate the fate of all sperm HSP70 isoforms during capacitation and in relation to sperm motility. Using Multiple-Reaction Monitoring (MRM) mass spectrometry, we showed that the relative abundance of all detected isoforms was stable between non-capacitated and capacitated spermatozoa. Immunofluorescence using two different antibodies also demonstrated the stability of HSP70 isoform localization during capacitation. We also investigated spermatozoa purified from 20 sperm samples displaying various levels of total and progressive sperm motility. We showed that the abundance of HSP70 isoforms is not correlated to sperm total or progressive motility.

Progesterone-Induced Sperm Release from the Oviduct Sperm Reservoir

In mammalian females, after sperm are deposited in the reproductive tract, a fraction of sperm migrates to the lower oviduct (isthmus) and forms a sperm storage site known as the functional sperm reservoir. The interactions between sperm membrane proteins and oviduct epithelial cells facilitate sperm binding to the oviductal epithelium and retention in the reservoir. Sperm are bound by glycans that contain specific motifs present on isthmic epithelial cells. Capacitated sperm are released from the reservoir and travel further in the oviduct to the ampulla where fertilization occurs. For decades, researchers have been studying the molecules and mechanisms of sperm release from the oviductal sperm reservoir. However, it is still not clear if the release of sperm is triggered by changes in sperm, oviduct cells, oviduct fluid, or a combination of these. While there is a possibility that more than one of these events are involved in the release of sperm from the reservoir, one activator of sperm release has the largest accumulation of supporting evidence. This mechanism involves the steroid hormone, progesterone, as a signal that induces the release of sperm from the reservoir. This review gathers and synthesizes evidence for the role of progesterone in inducing sperm release from the oviduct functional sperm reservoir.

The sodium-glucose cotransporter isoform 1 (SGLT-1) is important for sperm energetics, motility, and fertility†

Glucose is a key substrate for supporting sperm energy production and function. Previous studies have demonstrated that sperm glucose uptake is facilitated by several isoforms of the glucose transporters (GLUT). Here, we report that sperm also expresses the Na+-dependent sodium glucose cotransporter (SGLT). This was first suggested by our observation that genetic deletion of the testis-specific Na,K-ATPase α4, which impairs the sperm plasma membrane Na+ gradient, reduces glucose uptake and ATP production. Immunoblot analysis revealed the presence of an SGLT in sperm, with specific expression of isoform 1 (SGLT-1), but not of isoform 2 (SGLT-2). Immunocytochemistry identified SGLT-1 in the mid- and principal piece of the sperm flagellum. Inhibition of SGLT-1 with the isotype-selective inhibitor phlorizin significantly reduced glucose uptake, glycolytic activity, and ATP production in noncapacitated and capacitated sperm from wild-type mice. Phlorizin also decreased total sperm motility, as well as other parameters of sperm movement. In contrast, inhibition of SGLT-1 had no significant effect on sperm hyperactivation, protein tyrosine phosphorylation, or acrosomal reaction. Importantly, phlorizin treatment impaired the fertilizing capacity of sperm. Altogether, these results demonstrate that mouse sperm express a functional SGLT transport system that is important for supporting sperm energy production, motility, and fertility.

Mysteries and unsolved problems of mammalian fertilization and related topics

Mammalian fertilization is a fascinating process that leads to the formation of a new individual. Eggs and sperm are complex cells that must meet at the appropriate time and position within the female reproductive tract for successful fertilization. I have been studying various aspects of mammalian fertilization over 60 years. In this review, I discuss many different aspects of mammalian fertilization, some of my laboratory's contribution to the field, and discuss enigmas and mysteries that remain to be solved.

Oxidative Stress and Male Infertility: Evidence From a Research Perspective

Male fertility potential can be influenced by a variety of conditions that frequently coincide. Spermatozoa are particularly susceptible to oxidative damage due to their limited antioxidant capacity and cell membrane rich in polyunsaturated fatty acids (PUFAs). The role of oxidative stress (OS) in the etiology of male infertility has been the primary focus of our Stellenbosch University Reproductive Research Group (SURRG) over the last 10 years. This review aims to provide a novel insight into the impact of OS on spermatozoa and male reproductive function by reviewing the OS-related findings from a wide variety of studies conducted in our laboratory, along with those emerging from other investigators. We will provide a concise overview of the production of reactive oxygen species (ROS) and the development of OS in the male reproductive tract along with the physiological and pathological effects thereof on male reproductive functions. Recent advances in methods and techniques used for the assessment of OS will also be highlighted. We will furthermore consider the current evidence regarding the association between OS and ejaculatory abstinence period, as well as the potential mechanisms involved in the pathophysiology of various systemic diseases such as obesity, insulin resistance, hypertension, and certain mental health disorders which have been shown to cause OS induced male infertility. Finally, special emphasis will be placed on the potential for transferring and incorporating research findings emanating from different experimental studies into clinical practice.

Bundle formation of sperm: Influence of environmental factors

Cooperative behaviour of sperm is one of the mechanisms that plays a role in sperm competition. It has been observed in several species that spermatozoa interact with each other to form agglomerates or bundles. In this study, we investigate the effect of physical and biochemical factors that will most likely promote bundle formation in bull sperm. These factors include fluid viscosity, swim-up process, post-thaw incubation time and media additives which promote capacitation. While viscosity does not seem to influence the degree of sperm bundling, swim-up, post-thaw migration time and suppressed capacitation increase the occurrence of sperm bundles. This leads to the conclusion that sperm bundling is a result of hydrodynamic and adhesive interactions between the cells which occurs frequently during prolonged incubation times.

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

Simple Summary

Before the union of an egg and spermatozoon, several vital processes occur for fertilization in the female reproductive system. One of these processes is the maturation of spermatozoa which occurs in the female reproductive tract. Spermatozoa not undergoing maturation in the female reproductive tract are unable to penetrate the egg. Many reports have suggested the involvement of different factors in mediating the functional maturation of spermatozoa. Follicular fluid (FF) is named as one of those factors. FF is an ovarian fluid that plays an essential role in egg maturation and sources extracellular vesicles (EVs). EVs are nano-containers that are released from different cells and are present in all body fluids. Several studies have reported that FF supports the functional maturation of spermatozoa. Therefore, we hypothesized that FF EVs might have a role in inducing functional maturation in spermatozoa. Surprisingly, the FF-derived EVs were able to aid vital functional parameters of spermatozoa and the effects from EVs were species- and source-specific. Therefore, deciphering the cargo of FF EVs responsible for modulating spermatozoa’s functions can potentially prove beneficial in diagnosing and treating male infertility and improving the current assisted reproductive technology protocols.

Abstract

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.

Exogenous Albumin Is Crucial for Pig Sperm to Elicit In Vitro Capacitation Whereas Bicarbonate Only Modulates Its Efficiency

Simple Summary

In this work, we addressed if the presence of exogenous bicarbonate required for pig sperm capacitation, which is a necessary step to acquire fertilizing ability. While sperm incubated in media without BSA or BSA/bicarbonate did not achieve in vitro capacitation, those incubated with BSA reached that status under any bicarbonate concentration, even when bicarbonate was absent. Interestingly, there were differences related to the concentration of bicarbonate, since sperm incubated in media with BSA and with no bicarbonate or 5 mM bicarbonate showed lower overall efficiency in achieving in vitro capacitation than those incubated in the presence of BSA and higher concentration of bicarbonate. Additionally, at the end of the experiment, sperm incubated in the presence of BSA and 38 mM bicarbonate showed lower motility and plasma membrane integrity than those incubated in media with BSA and lower concentrations of bicarbonate. In conclusion, BSA is crucial in for pig sperm to elicit in vitro capacitation and trigger the subsequent progesterone-induced acrosome exocytosis. In contrast, although exogenous bicarbonate does not appear to be indispensable, it shortens the time needed to reach that capacitated status.

Abstract

This work sought to address whether the presence of exogenous bicarbonate is required for pig sperm to elicit in vitro capacitation and further progesterone-induced acrosome exocytosis. For this purpose, sperm were either incubated in a standard in vitro capacitation medium or a similar medium with different concentrations of bicarbonate (either 0 mM, 5 mM, 15 mM or 38 mM) and BSA (either 0 mg/mL or 5 mg/mL). The achievement of in vitro capacitation and progesterone-induced acrosomal exocytosis was tested through the analysis of sperm motility, plasma membrane integrity and lipid disorder, acrosome exocytosis, intracellular calcium levels, mitochondria membrane potential, O₂ consumption rate and the activities of both glycogen synthase kinase 3 alpha (GSK3α) and protein kinase A (PKA). While sperm incubated in media without BSA or BSA/bicarbonate, they did not achieve in vitro capacitation; those incubated in media with BSA achieved the capacitated status under any bicarbonate concentration, even when bicarbonate was absent. Moreover, there were differences related to the concentration of bicarbonate, since sperm incubated in media with BSA and with no bicarbonate or 5 mM bicarbonate showed lower overall efficiency in achieving in vitro capacitation than those incubated in the presence of BSA and 15 mM or 38 mM bicarbonate. Additionally, at the end of the experiment, sperm incubated in the presence of BSA and 38 mM bicarbonate showed significantly (p < 0.05) lower values of motility and plasma membrane integrity than those incubated in media with BSA and lower concentrations of bicarbonate. In conclusion, BSA is instrumental for pig sperm to elicit in vitro capacitation and trigger the subsequent progesterone-induced acrosome exocytosis. Furthermore, while exogenous bicarbonate does not seem to be essential to launch sperm capacitation, it does modulate its efficiency.

Physiologically detectable bisphenol A impairs human sperm functions by reducing protein-tyrosine phosphorylation

BACKGROUND

Bisphenol A (BPA), a widely used plastic monomer and plasticizer, is detectable in blood, urine and semen of a healthy people, with concentrations ranging from 0.1 nM to 10 nM. It has been shown that in vitro exposure of BPA as low as 0.001 nM could significantly inhibited mouse sperm motility and acrosome reaction. However, it is still unclear whether BPA at those physiologically detectable concentration affects human sperm.

METHODS

The effects of different concentrations of BPA (0, 10^-3, 10^-2, 10^-1, 10, 10³ nM) on sperm functions were examined, including human sperm viability, kinematic parameters, hyperactivation and capacitation.

RESULTS

BPA caused a remarkable decline in human sperm viability, motility and progressive motility, hyperactivation, capacitation and progesterone-induced acrosome reaction. Mechanism studies showed that BPA could suppress the protein tyrosine phosphorylation level of human sperm, but had no effect on sperm calcium signaling.

CONCLUSIONS

Physiologically detectable concentrations of BPA may impair human sperm functions via suppressing protein tyrosine phosphorylation of human sperm, implying that environmental pollution of BPA might be a factor contributing to male infertility.

Chronic testicular Chlamydia muridarum infection impairs mouse fertility and offspring development†

With approximately 131 million new genital tract infections occurring each year, Chlamydia is the most common sexually transmitted bacterial pathogen worldwide. Male and female infections occur at similar rates and both cause serious pathological sequelae. Despite this, the impact of chlamydial infection on male fertility has long been debated, and the effects of paternal chlamydial infection on offspring development are unknown. Using a male mouse chronic infection model, we show that chlamydial infection persists in the testes, adversely affecting the testicular environment. Infection increased leukocyte infiltration, disrupted the blood:testis barrier and reduced spermiogenic cell numbers and seminiferous tubule volume. Sperm from infected mice had decreased motility, increased abnormal morphology, decreased zona-binding capacity, and increased DNA damage. Serum anti-sperm antibodies were also increased. When both acutely and chronically infected male mice were bred with healthy female mice, 16.7% of pups displayed developmental abnormalities. Female offspring of chronically infected sires had smaller reproductive tracts than offspring of noninfected sires. The male pups of infected sires displayed delayed testicular development, with abnormalities in sperm vitality, motility, and sperm-oocyte binding evident at sexual maturity. These data suggest that chronic testicular Chlamydia infection can contribute to male infertility, which may have an intergenerational impact on sperm quality.

GIV/Girdin, a non-receptor modulator for Gαi/s, regulates spatiotemporal signaling during sperm capacitation and is required for male fertility

For a sperm to successfully fertilize an egg, it must first undergo capacitation in the female reproductive tract and later undergo acrosomal reaction (AR) upon encountering an egg surrounded by its vestment. How premature AR is avoided despite rapid surges in signaling cascades during capacitation remains unknown. Using a combination of conditional knockout (cKO) mice and cell-penetrating peptides, we show that GIV (CCDC88A), a guanine nucleotide-exchange modulator (GEM) for trimeric GTPases, is highly expressed in spermatocytes and is required for male fertility. GIV is rapidly phosphoregulated on key tyrosine and serine residues in human and murine spermatozoa. These phosphomodifications enable GIV-GEM to orchestrate two distinct compartmentalized signaling programs in the sperm tail and head; in the tail, GIV enhances PI3K→Akt signals, sperm motility and survival, whereas in the head it inhibits cAMP surge and premature AR. Furthermore, GIV transcripts are downregulated in the testis and semen of infertile men. These findings exemplify the spatiotemporally segregated signaling programs that support sperm capacitation and shed light on a hitherto unforeseen cause of infertility in men.

Prepubertal arsenic exposure alters phosphoproteins profile, quality, and fertility of epididymal spermatozoa in sexually mature rats

Arsenic intoxication affects male reproductive parameters of prepubertal rats. Besides, morphological and functional alterations in their testis and epididymis may remain after withdrawal of arsenic insult, causing potential impairment in male fertility during adulthood. In this study, we aimed at analyzing the effect of prepubertal arsenic exposure on the fecundity of epididymal sperm from sexually mature Wistar rats, assessing fertility indexes, sperm parameters, and sperm phosphoproteins content. Male pups on postnatal day (PND) 21 received filtered water (controls, n = 10) and 10 mg L^-1 arsenite (n = 10) daily for 30 days. From PND52 to PND81, rats from both groups received filtered water. During this period, the males mated with non-exposed females between PND72 and PND75. Our results showed that sexually mature rats presented low sperm production, epididymal sperm count, motility, and quality after prepubertal arsenic exposure. These findings possibly contributed to the low fertility potential and high preimplantation loss. Epididymal sperm proteome detected 268 proteins, which 170 were found in animals from both control and arsenic groups, 27 proteins were detected only in control animals and 71 proteins only in arsenic-exposed rats. In these animals, SPATA 18 and other five proteins were upregulated, whereas keratin type II cytoskeletal 1 was downregulated (q < 0.1). The results of KEGG pathway analysis demonstrated an enrichment of pathways related to dopaminergic response, adrenergic signaling, protein degradation, and oocyte meiosis in arsenic-exposed animals. Moreover, 26 proteins were identified by phosphoproteomic with different phosphorylation pattern in animals from both groups, but SPATA18 was phosphorylated only in arsenic-exposed animals. We concluded that prepubertal exposure to arsenic is deleterious to sperm quality and male fertility, altering the sperm phosphoproteins profile.

Bisphenol A and male murine reproductive system: finding a link between plasticizer and compromised health

The global burden of male infertility is rising at an alarming rate affecting the lives of millions in terms of physical, emotional and societal perspectives. Among several existing endocrine disrupting chemicals, bisphenol A (BPA) has been reported by many to inflict male reproductive toxicity in different experimental models, especially in mice. This review article critically discusses the overall reproductive toxicity of BPA with a special note to its ubiquitous existence, contamination route, effects on the reproductive system and toxicity mechanisms in male mice. Disturbed redox status in germ cells and spermatozoa plays a pivotal role in BPA induced male reproductive toxicity. In this context, the involvement of mitochondria and endoplasmic reticulum is also of grave importance. Induction of caspase-dependent apoptosis is the extreme consequence that leads to deterioration of cellular parameters. Besides the oxidative cellular and histoarchitectural damages, perturbed endocrine regulation, subsequent impaired hormonal and cellular genesis program, epigenetic alterations and inflammation cumulatively reflect poor sperm quality leading to compromised reproduction. Moreover, several key issues have also been highlighted that, if addressed, will strengthen our understanding of BPA mediated male reproductive toxicity.

IGF-1 supplementation in semen affects mitochondrial functional and calcium status of buffalo sperm following cryopreservation

This study was designed to examine the effects of seminal insulin-like growth factor-1 (IGF-1) supplementation on structural and functional properties of buffalo sperm post cryopreservation. Semen ejaculates from buffalo bulls (n = 6) were proportioned into four aliquots and diluted with egg yolk-based extender. Prior to equilibration, IGF-1 was added to extender as four treatments: group IGF0 (no supplementation), IGF150 (150 ng/mL), IGF250 (250 ng/mL) and IGF350 (350 ng/mL). The extended semen was transferred into 0.25 mL mini-straws, equilibrated (4 °C at 4 h), and cryopreserved. Total sperm motility was greater (P < 0.05) when there was the IGF150 treatment compared with values for other groups. Furthermore, with the IGF150 treatment there was the least and greatest (P < 0.05) mitochondrial superoxide status and membrane potential, respectively. Similarly, with the IGF150 treatment there was a greater (P < 0.05) sperm membrane integrity with a lesser (P < 0.05) calcium status compared to values for the other groups. In conclusion, seminal IGF-1 supplementation affects the structural and functional properties of buffalo sperm following cryopreservation.

Kinetic Study of 17α-Estradiol Activity in Comparison with 17β-Estradiol and 17α-Ethynylestradiol

17α-estradiol (αE2), an endogenous stereoisomer of the hormone 17β-estradiol (E2), is capable of binding to estrogen receptors (ER). We aimed to mathematically describe, using experimental data, the possible interactions between αE2 and sperm ER during the process of sperm capacitation and to develop a kinetic model. The goal was to compare the suggested kinetic model with previously published results of ER interactions with E2 and 17α-ethynylestradiol (EE2). The HPLC-MS/MS method was developed to monitor the changes of αE2 concentration during capacitation. The calculated relative concentrations Bt were used for kinetic analysis. Rate constants k and molar ratio n were optimized and used for the construction of theoretical B(t) curves. Modifications in αE2–ER interactions were discovered during comparison with models for E2 and EE2. These new interactions displayed autocatalytic formation of an unstable adduct between the hormone and the cytoplasmic receptors. αE2 accumulates between the plasma membrane lipid bilayer with increasing potential, and when the critical level is reached, αE2 penetrates through the inner layer of the plasma membrane into the cytoplasm. It then rapidly reacts with the ER and creates an unstable adduct. The revealed dynamics of αE2–ER action may contribute to understanding tissue rejuvenation and the cancer-related physiology of αE2 signaling.

Inhibition of human sperm motility and capacitation by ziram is mediated by decreasing tyrosine protein kinase

Many endocrine disruptors may interfere with sperm motility, hyperactivation, and capacitation, thereby leading to male infertility. In the current study, we screened 14 endocrine disruptors, including plant ingredients, cigarette ingredients, minerals, insecticides and fungicides, plastics, and plasticizers, to inhibit human sperm motility and forward motility. Only ziram, a dithiocarbamate fungicide, can effectively inhibit sperm motility, forward motility, hyperactivation, capacitation, and spontaneous acrosome reaction of normal human spermatozoa. Its half maximum inhibitory concentration (IC50) values were less than 4 μM. Ziram also inhibited sperm motility and forward motility of asthenozoospermia spermatozoa and IC50 values were about 6-8 μM. In addition, ziram inhibited normal sperm motility, calcium influx, reactive oxygen species, and mitochondrial membrane potential at 2.5 and/or 5 μM, with IC50 values ​​exceeding 100 μM, although it did not affect sperm DNA fragmentation up to 5 μM. Ziram-mediated inhibition of sperm motility and forward motility was irreversible. Forskolin, 8Br-cAMP, pentoxifylline, progesterone, vitamin E, and A23187 cannot prevent ziram-mediated inhibition of sperm motility and forward motility. Further studies have shown that ziram inhibited the level of tyrosine protein kinase with an IC50 value of about 10 μM, without affecting p21-activated kinase 4, and it caused damage to the mitochondrial structure of normal spermatozoa at 2.5 and 5 μM. In conclusion, ziram irreversibly inhibits human sperm motility, forward motility, and capacitation by reducing the level of tyrosine protein kinase and damaging the ultrastructure of mitochondria.

RNA-seq analysis of the mantle transcriptome from Mytilus edulis during a seasonal spawning event in deep and shallow water culture sites on the northeast coast of Newfoundland, Canada

The blue mussel (Mytilus edulis) has global commercial and ecological importance both in wild and cultured conditions. However there is a qualitative and quantitative lack of knowledge of the molecular mechanisms associated with its reproductive physiology, especially with reference to environmental interactions. Here we initiated a transcriptomic analysis (RNA-sequencing (RNA-seq)) of the mantle from both sexes sampled during a seasonal spawning event and from two culture depths (shallow-5 m; deep- 15 m). Mantle libraries were produced from 3 males and 3 females sampled from each of two shallow sites and two deep sites for a total of 12 replicate male and 12 replicate female libraries (24 total libraries). Overall a total of 2.3 billion raw 100 base reads with an average of 96.5 million reads/library were obtained and assembled into 296,118 transcripts with an average length of 568 bp. Overall, 315 transcripts from male libraries and 25 from female libraries were found to be upregulated in deep water as compared to shallow (edgeR adjusted p value ≤ 0.05). Conversely, 126 transcripts from male libraries and 135 from female libraries were found to be significantly downregulated at the same depth. Thirteen transcripts were selected for qPCR validation based on importance in reproduction, antimicrobial defense and metabolism. Of these, 9 RNA-seq identified transcripts were shown by qPCR to be differentially expressed between groups: 2 were upregulated in deep compared with shallow water (dhx38, mt-co1), 2 were upregulated for female compared with male mantle (pias2, mapkap1) and 6 genes (fndc3a, acbd3, klhl10, ccnb3, armc4, mt-co1) showed to be upregulated in males compared to females. The majority of qPCR studied transcripts were identified as involved in gamete development based on the UniProt database. This study further characterizes the importance of the mantle transcriptome during reproductive activities of M. edulis.

Multigenerational and transgenerational impact of paternal bisphenol A exposure on male fertility in a mouse model

STUDY QUESTION

How does paternal exposure to bisphenol A (BPA) affect the fertility of male offspring in mice in future generations?

SUMMARY ANSWER

Paternal exposure to BPA adversely affects spermatogenesis, several important sperm functions and DNA methylation patterns in spermatozoa, which have both multigenerational (in F0 and F1) and partial transgenerational (mainly noticed in F2, but F3) impacts on the fertility of the offspring.

WHAT IS KNOWN ALREADY

BPA, a synthetic endocrine disruptor, is used extensively to manufacture polycarbonate plastics and epoxy resins. Growing evidence suggests that exposure to BPA during the developmental stages results in atypical reproductive phenotypes that could persist for generations to come.

STUDY DESIGN, SIZE, DURATION

CD-1 male mice (F0) were treated with BPA (5 or 50 mg/kg body weight per day (bw/day)) or ethinylestradiol (EE) (0.4 μg/kg bw/day) for 6 weeks. Control mice were treated with vehicle (corn oil) only. The treated male mice were bred with untreated female mice to produce first filial generation (F1 offspring). The F2 and F3 offspring were produced similarly, without further exposure to BPA.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Histological changes in the testis along with functional, biochemical and epigenetic (DNA methylation) properties of spermatozoa were investigated. Subsequently, each parameter of the F0-F3 generations was compared between BPA-treated mice and control mice.

MAIN RESULTS AND THE ROLE OF CHANCE

Paternal BPA exposure disrupted spermatogenesis by decreasing the size and number of testicular seminiferous epithelial cells, which eventually led to a decline in the total sperm count of F0-F2 offspring (P < 0.05). We further showed that a high BPA dose decreased sperm motility in F0-F2 males by mediating the overproduction of reactive oxygen species (F0-F1) and decreasing intracellular ATP (F0-F2) in spermatozoa (P < 0.05). These changes in spermatozoa were associated with altered global DNA methylation patterns in the spermatozoa of F0-F3 males (P < 0.05). Furthermore, we noticed that BPA compromised sperm fertility in mice from the F0-F2 (in the both dose groups) and F3 generations (in the high-dose group only). The overall reproductive toxicity of BPA was equivalent to or higher (high dose) than that of the tested dose of EE.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Further research is required to determine the variables (e.g. lowest BPA dose) that are capable of producing changes in sperm function and fertility in future generations.

WIDER IMPLICATIONS OF THE FINDINGS

These results may shed light on how occupational exposure to BPA can affect offspring fertility in humans.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No. NRF-2018R1A6A1A03025159). M.S.R. was supported by Korea Research Fellowship Program through the NRF funded by the Ministry of Science and ICT (Grant No. 2017H1D3A1A02013844). There are no competing interests.

Characterization of Human Spermatic Subpopulations by ConA-Binding Sites and Tyrosine Phosphorylation during in vitro Capacitation and Acrosome Reaction

Spermatozoa capacitation is a time-dependent physiological process essential for acquiring the fertilizing capacity. In this context, reorganization of spermatozoa surface sugars and tyrosine phosphorylation are some of the most important biochemical changes involved in capacitation. However, the relationship between these 2 biomarkers remains poorly defined. By cytofluorescence we simultaneously characterized the head concanavalin A (ConA)-binding sites and the flagellar tyrosine phosphorylation before capacitation, during different capacitation times (1 and 4 h), and after acrosome reaction induction in human spermatozoa. The results showed a strong connection between ConA-label patterns and tyrosine phosphorylation according to the spermatozoa capacitation time and acrosomal status. Specifically, the spermatozoa subpopulation with phosphotyrosine presented proper sugar location (label in acrosomal and postacrosomal region) just after 1 h of capacitation, while cells without phosphotyrosine needed 4 h to do it. Moreover, after induction of spermatozoa acrosome reaction, phosphorylation was significantly correlated (p < 0.05) with the relocation of ConA-binding residues to the equatorial region, regardless of capacitation time. Overall, these observations provide novel insights regarding spermatozoa subpopulations based on essential physiological events like capacitation and acrosome reaction, which could have potential implications in the improvement of spermatozoa selection techniques.

Effects of phthalates on the functions and fertility of mouse spermatozoa

Phthalates are common environmental pollutants that are presumed to negatively impact male fertility including animals and humans. Particularly, these potential xenoestrogens may alter male fertility by binding to specific sperm receptors. Although several studies have characterized the toxic effects of single phthalates, epidemiological studies indicate that humans are typically exposed to phthalate mixtures. Here, we tested an environmental-related phthalate combination composed of 21 % di(2-ethylhexyl) phthalate, 15 % diisononyl phthalate, 8% diisobutyl phthalate, 15 % dibutyl phthalate, 35 % diethyl phthalate, and 5% benzylbutyl phthalate. Specifically, the effects of short-term exposure (90 min) to various concentrations (1, 10, 100, and 500 μg/mL) of this phthalate mixture on several important sperm processes, oocyte fertilization, and embryo production were assessed. All phthalate concentrations significantly decreased sperm motility and hyperactivity by compromising the sperm's ability to generate ATP. Additionally, short-term phthalate exposure (>10 μg/mL) also induced abnormal capacitation and the acrosome reaction by upregulating protein tyrosine phosphorylation via a protein kinase-A-dependent pathway. Furthermore, phthalate exposure (particularly at doses exceeding 10 μg/mL) significantly affected fertilization and early embryonic development. Together, our findings indicate that the studied phthalate mixtures adversely affected sperm motility, capacitation, and acrosome reaction, which resulted in poor fertilization rates and repressed embryonic development. Moreover, the lowest-observed-adverse-effect dose of the phthalate mixture tested can be assumed to be < 1 μg/mL in vitro.

Arylsulfatase A Remodeling during Human Sperm In Vitro Capacitation Using Field Emission Scanning Electron Microscopy (FE-SEM)

Capacitation drives sperm biophysical and biochemical changes for sperm-oocyte interactions. It is a well-known fact that the molecular complex arylsulfatase A (ARSA), hyaluronidase sperm adhesion molecule 1 (SPAM1), and heat shock protein 2 (HSPA2) plays a significant role in sperm-zona pellucida (ZP) binding. However, the time-dependent capacitation effects on the sperm surface ARSA presence and specific topographic distributions remain to be elucidated. Here, we quantified the ARSA density and specific membrane domain locations before (US) and after in vitro capacitation (one and four hours; CS1-CS4) in human sperm using high-resolution field emission scanning electron microscopy (FE-SEM) and immunogold labeling. Our results showed a significant and progressive capacitation-mediated increase of labeled spermatozoa from the US (37%) to CS4 (100%) physiological conditions. In addition, surface mapping revealed a close relationship between the ARSA residues and their acrosomal repositioning. Compared with the ARSA surface heterogeneous distribution found in US, the CS1-4 conditions exhibited clustering on the peri-acrosomal region, showing that time-dependent capacitation also induced a ARSA residue dramatic translocation on sperm surfaces. Our findings provide novel insights into the molecular remodeling events preceding sperm-oocyte interactions.

Effects of the environmental endocrine disruptors di-2-ethylhexyl phthalate and mono-2-ethylhexyl phthalate on human sperm function in vitro

Di-2-ethylhexyl phthalate (DEHP), a plastic-derived, endocrine-disrupting chemical, has been shown to exhibit male reproductive toxicity. However, its effects on human mature spermatozoa are largely unknown. In this study we investigated the invitro effects of DEHP and mono-2-ethylhexyl phthalate (MEHP; the main metabolite of DEHP) on sperm function and the mechanisms involved. Human spermatozoa were exposed to phthalates invitro at the doses that cover the concentrations detected in human semen: 20nM-8 μM DEHP, 1nM-20 μM MEHP or a mixture of 20nM-8 μM DEHP and 1nM-20 μM MEHP. DEHP and MEHP, alone or in combination, had no effect on the viability, membrane integrity, motility, homeostasis of reactive oxygen species or mitochondrial activity of human spermatozoa. Interestingly, 1nM-20 μM MEHP and combinations of 20nM-8 μM DEHP and 1nM-20 μM MEHP enhanced penetration ability, hyperactivation and the spontaneous acrosome reaction of human spermatozoa, and increased intracellular free Ca2+ concentrations ([Ca2+]i) and tyrosine phosphorylation, two key signalling pathways that regulate sperm function. The findings of this study suggest that invitro exposure to MEHP metabolised from DEHP affects human sperm function by inducing increases in sperm [Ca2+]i and tyrosine phosphorylation, which adds to our understanding of the effects of DEHP on male reproduction.