Members of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway are present and active in human sperm

CG9920 is necessary for mitochondrial morphogenesis and individualization during spermatogenesis in Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for investigating spermatogenesis due to its powerful genetics, conserved genes and visible morphology of germ cells during sperm production. Our previous work revealed that ocnus (ocn) knockdown resulted in male sterility, and CG9920 was identified as a significantly downregulated protein in fly abdomen after ocn knockdown, suggesting a role of CG9920 in male reproduction. In this study, we found that CG9920 was highly expressed in fly testes. CG9920 knockdown in fly testes caused male infertility with no mature sperms in seminal vesicles. Immunofluorescence staining showed that depletion of CG9920 resulted in scattered spermatid nuclear bundles, fewer elongation cones that did not migrate to the anterior region of the testis, and almost no individualization complexes. Transmission electron microscopy revealed that CG9920 knockdown severely disrupted mitochondrial morphogenesis during spermatogenesis. Notably, we found that CG9920 might not directly interact with Ocn, but rather was inhibited by STAT92E, which itself was indirectly affected by Ocn. We propose a possible novel pathway essential for spermatogenesis in D. melanogaster, whereby Ocn indirectly induces CG9920 expression, potentially counteracting its inhibition by the JAK-STAT signaling pathway.

The Regulatory Effects of JAK2/STAT3 on Spermatogenesis and the Redox Keap1/Nrf2 Axis in an Animal Model of Testicular Ischemia Reperfusion Injury

The male reproductive system requires the pleiotropic activity of JAK/STAT to maintain its function, especially spermatogenesis. The study aims to investigate the effect of JAK2 signaling on the expression of the Keap1/Nrf2 axis, spermatogenesis, and the Sertoli cells (Sc) junctions in an animal model of testicular ischemia reperfusion injury (tIRI). Testes subjected to tIRI exhibited increased JAK2/STAT3 activity associated with spermatogenic arrest and reduced expression of the Sc junctions. In addition, there was an increased protein expression of Keap1 and decreased Nrf2., which was coupled with the downregulation of gene expression of antioxidant enzymes. Reduced SOD and CAT activities were accompanied by increased lipid peroxidation and protein carbonylation during tIRI. Increased caspase 9 activity and Bax/Bcl2 ratio indicated initiation of apoptosis. Inhibition of JAK2 activity by AG490 maintained the integrity of spermatogenesis and SC junctions, normalized the expression of the Keap1/Nrf2 axis and its downstream antioxidant enzymes, and prevented germ cell apoptosis. The results further emphasized the regulatory role of JAK2/STAT3 on spermatogenesis, Keap1/Nrf2 signaling, and maintenance of the testicular redox balance to combat testicular dysfunction and male infertility.

Whole-Genome Profile of Greek Patients with Teratozοοspermia: Identification of Candidate Variants and Genes

Male infertility is a global health problem that affects a large number of couples worldwide. It can be categorized into specific subtypes, including teratozoospermia. The present study aimed to identify new variants associated with teratozoospermia in the Greek population and to explore the role of genes on which these were identified. For this reason, whole-genome sequencing (WGS) was performed on normozoospermic and teratozoospermic individuals, and after selecting only variants found in teratozoospermic men, these were further prioritized using a wide range of tools, functional and predictive algorithms, etc. An average of 600,000 variants were identified, and of them, 61 were characterized as high impact and 153 as moderate impact. Many of these are mapped in genes previously associated with male infertility, yet others are related for the first time to teratozoospermia. Furthermore, pathway enrichment analysis and Gene ontology (GO) analyses revealed the important role of the extracellular matrix in teratozoospermia. Therefore, the present study confirms the contribution of genes studied in the past to male infertility and sheds light on new molecular mechanisms by providing a list of variants and candidate genes associated with teratozoospermia in the Greek population.

Wenshenyang recipe treats infertility through hormonal regulation and inflammatory responses revealed by transcriptome analysis and network pharmacology

The Wenshenyang recipe (WSYR) has the effect of treating infertility, but the mechanisms underlying this activity have not been fully elucidated. In this study, network pharmacology and RNA sequencing were combined, with database-based “dry” experiments and transcriptome analysis-based “wet” experiments used conjointly to analyse the mechanism of WSYR in the treatment of infertility. In the dry analysis, 43 active compounds in WSYR and 44 therapeutic targets were obtained through a database search, 15 infertility pathways were significantly enriched, and key targets, such as ESR1, TP53, AKT1, IL-6, and IL-10 were identified. Then the wet experiments were performed to detect the expression changes of the 412 genes from 15 infertility pathways identified by dry analysis. HK-2 cells were treated with the three herbs of WSYR and subjected to targeted RNA sequencing. Based on the results, 92 of the 412 genes in 15 infertility pathways were identified as DEGs. Additionally, key targets, such as ESR2, STAT1, STAT3, and IL6, were also identified in the wet experiments. RT-qPCR experiments further verified that WSYR played an anti-inflammatory role by upregulating IL-4 and IL-10 and Epimedium brevicornu Maxim (Yinyanghuo) showed broader effect than Drynaria fortunei (Kunze) J. Sm (Gusuibu) and Cistanche deserticola Y.C.Ma (Roucongrong). By screening compounds of WSYR using molecular docking models of ESR1 and ESR2, it was further found that xanthogalenol in Gusuibu, arachidonate in Roucongrong, and anhydroicaritin in Yinyanghuo had good affinity for estrogen receptors. These findings provide evidence for an estrogen-regulating role of the three herbs in WSYR.

Sperm-oviduct interaction: Differential gene expression of growth factors induced by sperm DNA fragmentation

The present study investigated the effects of DNA fragmentation of spermatozoa on the growth factors expression by a human oviduct epithelial cell line (OE-E6/E7). Two separate groups were examined in this study. The cell line was cultured in the presence of spermatozoa with normal DNA fragmentation index (DFI) or abnormal DFI. Total RNA from the cell line in each group was isolated, and relative expression of objective genes was analysed using PCR array. Also, the concentration of VEGF, BMP-2, BMP-7 and MSTN in the supernatant of cell culture was analysed by the ELISA method. The PCR array analysis revealed that most of the growth factors had been upregulated in the abnormal group. However, the differences between groups were statistically significant (p < 0.05) for five genes, including VEGF-A, BMP-2, BMP-6, BMP-7 and OSM. Furthermore, MSTN was the only gene that down-regulated significantly under the influence of the spermatozoa with abnormal DFI. Moreover, the results of ELISA analysis were in agreement with the data of the PCR array. It has been concluded that DNA fragmentation in human spermatozoa can probably change regular events throughout the oviducts. Consequently, the genes of interest may change sperm function and probably its fate in the female reproductive tract.

MicroRNA-222 Transferred From Semen Extracellular Vesicles Inhibits Sperm Apoptosis by Targeting BCL2L11

Seminal plasma contains a large number of extracellular vesicles (EVs). However, the roles of these EVs and their interactions with sperm are not clear. To identify the important molecules affecting sperm motility in EVs, we analyzed RNA from seminal plasma EVs of boars with different sperm motility using whole-transcriptome sequencing and proteomic analysis. In total, 7 miRNAs, 67 lncRNAs, 126 mRNAs and 76 proteins were differentially expressed between the two groups. We observed that EV-miR-222 can obviously improve sperm motility. In addition, the results suggested that miR-222 was transferred into sperm by the EVs and that miR-222 affected sperm apoptosis by inhibiting the expression of EGFR, BCL2L11, BAX, CYCs, CASP9 and CASP3. The results of electron microscopy also showed that overexpression of miR-222 in EVs could reduce sperm apoptosis. The study of the whole transcriptomes and proteomes of EVs in boar semen revealed some miRNAs may play an important role in these EVs interactions with Duroc sperm, and the findings suggest that the release of miR-222 by semen EVs is an important mechanism by which sperm viability is maintained and sperm apoptosis is reduced. Our studies provide a new insight of miR-222 in EVs regulation for sperm motility and sperm apoptosis.

Biological Network Model of Effect of Chronic Intermittent Hypoxia on Spermatogenesis in Rats

Background

The aim of this study was to explore the effect of obstructive sleep apnea hypopnea syndrome (OSAHS) on spermatogenesis and the effects of the expression of related proteins.

Material/Methods

Rats in Group A were normoxic (exposed to a normal level of oxygen). Rats in Group B were exposed to intermittent hypoxia. After 6 weeks, the rats were killed and their epididymides were removed. The epididymis of one testis was used to test indices of semen quality. The epididymis of the other testis was stained with hematoxylin & eosin to observe pathologic changes in the testis. We used real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting to measure expression of the protein and mRNA of leptin, Janus kinase (JAK), and signal transducer and activator of transcription (STAT) in rat testicular cells. Cytoscape v3.7.1 was employed to construct the OSAHS–male infertility network and protein–protein interactions network. Information on common targets of OSAHS and male infertility was imported into the Database for Annotation, Visualization and Integrated Discovery (DAVID). Then, analyses of pathway enrichment were undertaken using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases.

Results

Data were obtained 6 weeks after completion of OSAHS modeling. Compared with Group A, the total sperm count and sperm motility in Group B showed a downward trend (P<0.05). Staining showed no obvious abnormality in Group A. However, numerous structurally abnormal spermatogenic tubules were observed in Group B samples, and the lumen was atrophied and thinned, arranged unevenly, and the gap between the tubules was markedly increased. Western blotting and RT-qPCR showed that, compared with Group A, expression of the protein and mRNA of leptin, JAK, and STAT in the testes of rats in Group B was significantly increased (P<0.05 for all).

Conclusions

These data suggest that: (1) Chronic intermittent hypoxia can cause pathologic damage to rat testes; (2) Oligozoospermia was highly correlated and regulated by the JAK2/STAT6 signaling pathway; and (3) Chronic intermittent hypoxia can lead to decreased spermatogenesis in rats.

miR-142-5p/DAX1-dependent regulation of P450c17 contributes to triclosan-mediated testosterone suppression

Triclosan (TCS) is a potent antibacterial and antifungal compound that is extensively used in various daily products. TCS is also considered as an underlying endocrine disruptor and has anti-androgenic effects. In our previous work, we found that TCS suppressed testicular steroidogenesis via the miR-6321/JNK/Nur77 cascade, but roles of the abnormal expression of miR-142-5p and P450c17 in this molecular event were still unknown. Therefore, to verify the hypothesis that miR-142-5p and P450c17 might significantly function in other manner in testosterone decline after TCS exposure, Sprague-Dawley rats and the rat Leydig cell line were used in this study. Results showed that after TCS exposure, testicular histomorphology was abnormally changed and testosterone level was declined. Overexpressed miR-142-5p by TCS directly targeted the JAK1/STAT1 pathway. Bidirectional Co-IP assays and the use of STAT1 activator demonstrated that STAT1 could interact with and regulate Sp1. The activity, mRNA level, and protein expression of DNMT1 and DNMT3β were all decreased after TCS treatment. Sp1 silencing, ChIP, and qPCR assays showed that Sp1 regulated DNMT1 expressions by directly binding to the promoter region of DNMT1. Though the DNA methylation status of the DAX1 promoter was not affected, TCS induced the transcription and translation of DAX1 by DNMT1, in turn leading to the inhibition of steroidogenic P450c17. Taken together, TCS-induced miR-142-5p inhibits P450c17 by the JAK1/STAT1 pathway and downstream Sp1/DNMT1/DAX1 cascade, finally facilitating the decrease in testosterone levels.

Integrated analysis miRNA and mRNA profiling in patients with severe oligozoospermia reveals miR-34c-3p downregulates PLCXD3 expression

Our previous research suggested that an integrated analysis of microRNA (miRNA) and messenger RNA (mRNA) expression is helpful to explore miRNA-mRNA interactions and to uncover the molecular mechanisms of male infertility. In this study, microarrays were used to compare the differences in the miRNA and mRNA expression profiles in the testicular tissues of severe oligozoospermia (SO) patients with obstructive azoospermia (OA) controls with normal spermatogenesis. Four miRNAs (miR-1246, miR-375, miR-410, and miR-758) and six mRNAs (SLC1A3, PRKAR2B, HYDIN, WDR65, PRDX1, and ADATMS5) were selected to validate the microarray data using quantitative real-time PCR. Using statistical calculations and bioinformatics predictions, we identified 33 differentially expressed miRNAs and 1,239 differentially expressed mRNAs, among which one potential miRNA-target gene pair, miR-34c-3p and PLCXD3 (Phosphatidylinositol-Specific Phospholipase C, X Domain Containing 3), was identified. Immunohistochemical analysis indicated that PLCXD3 was located within the germ cells of the mouse and human testis. Moreover, we found that miR-34c-3p was able to decrease PLCXD3 expression in mouse (GC-1 and TM4) and human (NCM460) cell lines, presumably indicating the possibility that miR-34c-3p acts as an intracellular mediator in germinal lineage differentiation. Notably, we reported the expression of the PLCXD3 protein in a man with normal spermatogenesis and the lack of the PLCXD3 protein in a man with SO. Therefore, the identified miRNA and mRNA may represent a potentially novel molecular regulatory network and therapeutic targets for the study or treatment of SO, which might provide a better understanding of the molecular basis of spermatogenesis dysfunction.

Profiling signaling proteins in human spermatozoa: biomarker identification for sperm quality evaluation

OBJECTIVE

To determine the correlation between semen basic parameters and the expression and activity of signaling proteins.

DESIGN

In vitro studies with human spermatozoa.

SETTING

Academic research institute.

PATIENT(S)

Thirty-seven men provided semen samples for routine analysis.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Basic semen parameters tracked included sperm DNA fragmentation (SDF), the expression levels of 75 protein kinases, and the phosphorylation/cleavage patterns of 18 signaling proteins in human spermatozoa.

RESULT(S)

The results indicated that the phosphorylated levels of several proteins (Bad, GSK-3β, HSP27, JNK/SAPK, mTOR, p38 MAPK, and p53), as well as cleavage of PARP (at D214) and Caspase-3 (at D175), were significantly correlated with motility parameters. Additionally, the percentage of morphologically normal spermatozoa demonstrated a significant positive correlation with the phosphorylated levels of p70 S6 kinase and, in turn, head defects and the teratozoospermia index (TZI) showed a significant negative correlation with the phosphorylated levels of Stat3. There was a significant positive correlation between SDF and the teratozoospermia index, as well as the presence of head defects. In contrast, SDF negatively correlated with the percentage of morphologically normal spermatozoa and the phosphorylation of Akt and p70 S6 kinase. Subjects with varicocele demonstrated a significant negative correlation between head morphological defects and the phosphorylated levels of Akt, GSK3β, p38 MAPK, and Stat1. Additionally, 34 protein kinases were identified as expressed in their total protein levels in normozoospermic samples.

CONCLUSION(S)

This study contributed toward establishing a biomarker "fingerprint" to assess sperm quality on the basis of molecular parameters.

IFN-gamma alters the human sperm membrane permeability to Ca(2+)

Inflammation in the male genitourinary tract has been associated with the release of pro-inflammatory cytokines such as interferon-gamma (IFN-γ) and elevated reactive oxygen species, which affects spermatozoa capacitation, motility, and the acrosome reaction, along with functions regulated by the concentration of cytoplasmic Ca(2+) ([Ca(2+)]cyto). Though Ca(2+) signaling is of particular significance in sperm, the effect of IFN-γ intracellular calcium on these cells is still unknown. The present study evaluated the effect of IFN-γ on the [Ca(2+)]cyto and Ca(2+) permeability on human sperm. A cell suspension loaded with fura-2 was incubated with or without IFN-γ (from 0 to 2000 pg/ml) for 0, 30, 60, and 120 minutes, and the [Ca(2+)]cyto was measured. The permeability to Ca(2+) was evaluated by the change of the intracellular concentration following an extracellular Ca(2+) pulse. IFN-γ at low concentrations (≤ 500  pg/ml) did not affect the [Ca(2+)]cyto and Ca(2+) permeability of sperm. At a high concentration (2000  pg/ml), IFN-γ did not alter the [Ca(2+)](cyto), but significantly decreased the magnitude and velocity of Ca(2+) entry into the cell. This effect was dependent on incubation time and IFN-γ concentration. This alteration induced by IFN-γ was prevented by the simultaneous incubation of sperm with the antioxidant butylhydroxytoluene (BHT). In conclusion, in vitro, IFN-γ modifies Ca(2+) sperm membrane permeability, probably via lipid peroxidation. IFN-γ in high concentration, as observed in inflammation/infection, can affect [Ca(2+)](cyto) regulation and alter sperm fertilizing capacity.

Stattic V, a STAT3 inhibitor, affects human spermatozoa through regulation of mitochondrial activity

We have recently shown that many mediators of the JAK/STAT signaling pathway are present in ejaculated human spermatozoa. Among them, STAT3 is detected mainly in membranes and flagellar cytoskeletal fractions. In order to determine the importance of STAT3-mediated signaling, sperm were incubated with Stattic V, a specific inhibitor. Effects on motility were evaluated by CASA, sperm acrosomal integrity was evaluated by FITC conjugated lectin (PSA or PNA) staining, and protein phosphotyrosine content was assessed by Western blot using a monoclonal anti-phosphotyrosine antibody. INDO1-AM and JC-1 were used to measure sperm intracellular calcium and mitochondrial membrane potential, respectively, by flow cytometry, and reactive oxygen species (ROS) production was investigated by luminol-based assay. Percentages of motility and motility parameters were significantly affected by Stattic V. This later also significantly increased intracellular Ca(2+) levels, progesterone- and calcium ionophore (A23187)-induced acrosome reaction. On the other hand, a significant decrease in ATP content was measured when sperm were treated with Stattic V, associated with depolarization of mitochondrial membrane and elevated ROS production. These results suggest that STAT3 is involved in sperm functions, at least through regulation of mitochondrial activity. This further emphasizes that STAT3 mediates cellular activities in a manner different than strictly the activation of gene transcription.

Progesterone activates Janus Kinase 1/2 and activators of transcription 1 (JAK1-2/STAT1) pathway in human spermatozoa

Ejaculated spermatozoa undergo capacitation and acrosome reaction by responding to extrinsic clues and activate signalling cascades to induce protein tyrosine phosphorylation. In the present study, we investigated the existence, the Janus kinase (JAK) and activator of transcription (STAT) pathway and determined its physiological relevance. JAK1 and STAT1 are localised on the equatorial region and the midpiece of their human spermatozoa, JAK2 is detected on the sperm tail. Capacitation leads to phosphorylation of JAK2 but not JAK1 and STAT1. In the uncapacitated sperm, phosphorylated JAK2 (pJAK2) is localised mainly in the tail region; in response to capacitation, the JAK2 is phosphorylated in the midpiece and the head region along with the tail. Progesterone (5 μm) leads to phosphorylation of JAK1, JAK2 and STAT1 in a time-dependent manner. In progesterone-treated spermatozoa, the JAK2 in the tail is hyperphosphorylated, the JAK2 in the head and the midpiece is dephosphorylated. We conclude that in human spermatozoa, the JAK1/2 pathway is activated upon capacitation and is further modulated by progesterone; the biological processes controlled by this pathway in sperm need to be elucidated.

Mediators of the Jak/STAT signaling pathway in human spermatozoa

In their journey to acquire the ability to fertilize the egg, numerous intracellular signaling systems are activated in spermatozoa, leading to an increase in protein tyrosine phosphorylation. Although the JAK/STAT signaling pathway is usually associated with the activation of transcription of specific genes, our laboratory previously demonstrated the presence of the IL6 receptor (IL6R) and the Janus kinase 1 (JAK1) in human spermatozoa, a cell that is mostly transcriptionally inactive. In order to determine the importance of the JAK/STAT signaling pathway, our objectives were to identify and characterize the mediators of this system in human sperm. Cell fractionation and surface biotinylation assays clearly demonstrated that IL6R is expressed at the sperm membrane surface. The kinase JAK1 is enriched in membrane fractions and is activated during human sperm capacitation as suggested by its increase in phosphotyrosine content. Many signal transducer and activator of transcription (STAT) proteins are expressed in human sperm, including STAT1, STAT3, STAT4, STAT5, and STAT6. Among them, only STAT1 and STAT5 were detected in the cytosolic fraction. All the detected STAT proteins were enriched in the cytoskeletal structures. STAT4 was present in the perinuclear theca, whereas JAK1, STAT1, and STAT5 were detected in the fibrous sheath. Indirect immunofluorescence studies showed that JAK1 and STAT1 colocalized in the neck region and that STAT4 is present at the equatorial segment and flagella. The presence of STAT proteins in sperm structural components suggests that their role is different from their well-known transcription factor activity in somatic cells, but further investigations are required to determine their role in sperm function.

Computational identification of transcription frameworks of early committed spermatogenic cells

It is known that transcription factors (TFs) work in cooperation with each other to govern gene expression and thus single TF studies may not always reflect the underlying biology. Using microarray data obtained from two independent studies of the first wave of spermatogenesis, we tested the hypothesis that co-expressed spermatogenic genes in cells committed to differentiation are regulated by a set of distinct combinations of TF modules. A computational approach was designed to identify over-represented module combinations in the promoter regions of genes associated with transcripts that either increase or decrease in abundance between the first two major spermatogenic cell types: spermatogonia and spermatocytes. We identified five TFs constituting four module combinations that were correlated with expression and repression of similarly regulated genes. These modules were biologically assessed in the context that they represent the key transcriptional mediators in the developmental transition from the spermatogonia to spermatocyte.

In spermatozoa, Stat1 is activated during capacitation and the acrosomal reaction

A role for sperm-specific proteins during the early embryonic development has been suggested by a number of recent studies. However, little is known about the participation of transcription factors in that stage. Here, we show that the signal transducer and activator of transcription 1 (Stat1), but not Stat4, was phosphorylated in response to capacitation and the acrosomal reaction (AR). Moreover, Stat1 phosphorylation correlated with changes in its localization: during capacitation, Stat1 moved from the cytoplasm to the theca/flagellum fraction. During AR, Stat1 phosphorylation increased again. In addition, blocking protein kinase A (PKA) and PKC during capacitation abolished both phosphorylation and migration of Stat1. Our results show tight spatio-temporal rearrangements of Stat1, suggesting that after fertilization Stat1 participates in the first rounds of transcription within the male pronucleus.

Sperm lipid peroxidation and pro-inflammatory cytokines

AIM

To investigate if interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), interferon-gamma (IFN-gamma) or tumor necrosis factor-alpha (TNF-alpha) are able to stimulate the level of lipid peroxidation of sperm membranes, either alone or in the presence of leukocytes.

METHODS

Semen samples from normozoospermic donors were prepared by density gradient. The sperms were exposed to the indicated cytokines, at physiological and infection-inflammation concentrations, in the absence or presence of leukocytes. Lipid peroxidation of the sperm membranes was determined by measuring malondialdehyde (MDA) and 4-hydroxialkenals (HAE) formation.

RESULTS

TNF-alpha, IL-8 and IFN-gamma increased the level of sperm membrane lipid peroxidation when tested at physiological concentrations. At infection-inflammation concentrations, only IL-8 was able to produce a higher effect. When assayed in the presence of leucocytes, IL-8 and TNF-alpha showed a higher effect at infection-inflammation concentrations than at physiological concentrations. Finally, IL-8 showed a higher effect in the presence of leukocytes than in their absence at both physiological and infection-inflammation concentrations. TNF-alpha also showed a higher effect when assayed in the presence of leukocytes than in their absence, but only at infection-inflammation concentrations. There was no effect of IL-6 or IL-10 in any of the tested conditions.

CONCLUSION

Several pro-inflammatory cytokines at physiological concentrations increase the level of lipid peroxidation of sperm membranes, which could be important for the sperm fecundation process. However, infection-inflammation concentrations of some cytokines, such as IL-8 and TNF-alpha, either alone or in the presence of leukocytes, could drive the lipid peroxidation of the spermatozoa plasma membrane to levels that can affect the sperm fertility capacity.

Identification of the proteins present in the bull sperm cytosolic fraction enriched in tyrosine kinase activity: a proteomic approach

Numerous sperm proteins have been identified on the basis of their increase in tyrosine phosphorylation during capacitation. However, the tyrosine kinases present in spermatozoa that are responsible for this phosphorylation remain unknown. As spermatozoa are devoid of transcriptional and translational activities, molecular biology approaches might not reflect the transcriptional pattern in mature spermatozoa. Working directly with the proteins present in ejaculated spermatozoa is the most reliable approach to identify the tyrosine kinases potentially involved in the capacitation-associated increase in protein tyrosine phosphorylation. A combination of tyrosine kinase assays and proteomic identification tools were used as an approach to identify sperm protein tyrosine kinases. Fractionation by nitrogen cavitation showed that the majority of tyrosine kinase activity is present in the cytosolic fraction of bovine spermatozoa. By the use of Poly-Glu:Tyr(4:1)-agarose affinity chromatography, we isolated a fraction enriched in tyrosine kinase activity. Proteomics approaches permitted the identification of tyrosine kinases from three families: Src (Lyn), Csk, and Tec (Bmx, Btk). We also identified proteins implicated in different cellular events associated with sperm capacitation and acrosome reaction. These results confirm the implication of tyrosine phosphorylation in some aspects of capacitation/acrosome reaction and reveal the identity of new players potentially involved in these processes.

Pathogenic Consequences in Semen Quality of an Autoimmune Response against the Prostate Gland: From Animal Models to Human Disease

We have recently proposed an autoimmune etiology in approximately 35% of chronic nonbacterial prostatitis patients, the most frequent form of prostatitis observed, because they exhibit IFN-gamma-secreting lymphocytes specific to prostate Ags. Interestingly, this particular group of patients, but not the rest of chronic nonbacterial prostatitis patients, also presented striking abnormalities in their semen quality. In this work, we use an experimental animal model of autoimmune prostatitis on Wistar rats developed in our laboratory to investigate when, where, and how sperm cells from autoimmune prostatitis individuals are being damaged. As in patients, a marked reduction in sperm concentration, almost null sperm motility and viability, and an increased percentage of apoptotic spermatozoa were detected in samples from animals with the disease. Prostate-specific autoantibodies as well as elevated levels of NO, TNF-alpha, and IFN-gamma were also detected in their seminal plasma. In contrast, epididymal spermatozoa remain intact, indicating that sperm damage occurs at the moment of joining of prostate secretion to sperm cells during ejaculation. These results were further supported by experiments in which mixture of normal sperm cells with autoimmune seminal plasma were performed. We hypothesize that sperm damage in experimental autoimmune prostatitis can be the consequence of an inflammatory milieu, originally produced by an autoimmune response in the prostate; a diminished prostate functionality, evidenced by reduced levels of citric acid in semen or by both mechanisms simultaneously. Once more, we suggest that autoimmunity to prostate may have consequences on fertility.

Bull testicular haploid germ cells express a messenger encoding for a truncated form of the protein tyrosine kinase HCK

Protein tyrosine phosphorylation is a process that has been studied worldwide during sperm capacitation and acrosomal exocytosis events. Although few capacitation-induced phosphotyrosine-containing proteins have been identified, little is known about the tyrosine kinases directly involved in this post-translational modification. Different studies from our and other groups using tyrosine kinase inhibitors suggest the involvement of members of the family of src-related tyrosine kinases in the sperm capacitation associated increase in protein tyrosine phosphorylation. Using a molecular biology approach, we report for the first time messengers encoding for members from the src-related tyrosine kinase family in bovine spermatogenic cells. Degenerated primers were designed within a highly homologous region specific to the family of src tyrosine kinases, and RNAs coding for c-src, c-yes, lyn, lck, and hck were identified in bull testis and haploid germ cells by RT-PCR. We also report the presence of a messenger in haploid bull germ cells that could encode for a truncated isoform of the hck tyrosine kinase. This messenger was detected by screening of a haploid germ cells cDNA library using the RT-PCR product homologous to hck as a probe. The presence of this transcript in haploid germ cell RNA preparations was validated by RT-PCR, 3'RACE, 5'RACE as well as Northern blot. Such a truncated protein could function as an adaptor protein or as a competitive inhibitor in spermiogenesis or mature sperm functions.

Effect of Cryopreservation on Sea Bass Sperm Proteins

In the present study we used two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-associated laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to verify whether the protein expression of sea bass sperm was affected by the cryopreservation procedure. The protein profiles differed between fresh and frozen-thawed semen as revealed by visual inspection and by image analysis software. We identified 163 spots in fresh sperm; among these, 13 were significantly decreased and 8 were absent in two-dimensional gel obtained with cryopreserved sperm. Five of these spots were analyzed with MALDI-TOF, but only three showed a significant match in the databases used in bio-informatics analysis (PeptIdent, Mascot, and MS-Fit). In particular, spot 5 showed homology with a novel protein of zebrafish (similar to SKB1 of human and mouse), spot 13 showed homology with amphibian G1/S-specific cyclin E2, and spot 20 showed homology with the hypothetical protein DKFZp566A1524 of Brachidanio rerio. The present work shows that the use of the cryopreservation procedure causes the degradation of sperm proteins and among these, two could be at least partially responsible for the observed decrease in sperm motility duration and the lower hatching rate of eggs fertilized with cryopreserved sperm.

Induction of human sperm capacitation and protein tyrosine phosphorylation by endometrial cells and interleukin-6*

In order to become fully competent at fertilizing the oocyte, spermatozoa must undergo the maturational process of capacitation during their journey in the female reproductive tract. Endometrial cells secrete an array of growth factors that can affect spermatozoa. Among these factors, it has been previously demonstrated that interleukin-6 (IL-6) affects the fertilizing capacity of human spermatozoa. As the expression of this cytokine varies throughout the menstrual cycle and increases during the periovulatory period, the involvement of IL-6 in human sperm capacitation was investigated, with emphasis on the signal transduction cascade triggered by this agent in sperm cells. Spermatozoa were treated with recombinant human IL-6. Protein phosphotyrosine content and localization of the phosphotyrosine containing proteins were evaluated by western blot and indirect immunofluorescence, respectively, using a monoclonal anti-phosphotyrosine antibody. The acrosomal status was evaluated on IL-6 treated spermatozoa before or after challenge with the ionophore A23187 according to the fluorescent pattern observed upon binding to the Pisum sativum agglutinin conjugated to fluorescein isothiocyanate. In the present study, it is shown that, as for endometrial cell-conditioned media, IL-6 induces human sperm capacitation. The IL-6 effects most likely occur through binding to its receptor, IL-6Ralpha, whose presence in the sperm is also reported in this study. As for the IL-6 receptor, this is the first report on the presence of the tyrosine kinase JAK1 in the spermatozoa. Moreover, this kinase becomes phosphorylated on tyrosine residues upon sperm treatment with recombinant IL-6, which suggests its activation by the cytokine. Taken together, our results demonstrate that the IL-6 intracellular signalling machinery is present in human spermatozoa and might be involved in the acquisition of sperm fertilizing ability, also known as the capacitation process.

Interactions of sperm perinuclear theca with the oocyte: implications for oocyte activation, anti-polyspermy defense, and assisted reproduction

Perinuclear theca (PT) is the cytoskeletal coat of mammalian sperm nucleus that is removed from the sperm head at fertilization. PT harbors the sperm borne, oocyte-activating factor (SOAF), a yet-to-be-characterized substance responsible for triggering the signaling cascade of oocyte activation, thought to be dependent on intra-oocyte calcium release. The present article reviews the current knowledge on the biogenesis and molecular composition of sperm PT. Possible functions of sperm PT during natural and assisted fertilization, and in the initiation of embryonic development are discussed. Furthermore, evidence is provided that SOAF is transferred from the sperm PT to oocyte cytoplasm through the internalization and rapid solubilization of the post-acrosomal PT. It is shown that during natural fertilization the sperm PT dissolves in the oocyte cytoplasm concomitantly with sperm nuclear decondensation and the initiation of pronuclear development. SOAF activity is preserved in the differentially extracted sperm heads only if the integrity of PT is maintained. After intracytoplasmic sperm injection (ICSI), activation occurs only in those oocytes in which the injected spermatozoon displays complete or partial dissolution of PT. In the latter case, the residual PT of the sub-acrosomal and/or post-acrosomal sperm region may persist on the apical surface of the sperm nucleus/male pronucleus and may cause a delay or arrest of zygotic development. We propose that the sperm PT harbors SOAF in the post-acrosomal sheath, as this is the first part of the sperm cytosol to enter the oocyte cytoplasm and its disassembly appears sufficient to initiate the early events of oocyte activation. Dissolution of the sub-acrosomal part of the PT, on the other hand, appears necessary to insure complete DNA decondensation in the internalized sperm nucleus and initiate DNA synthesis of both pronuclei. The release of the SOAF from the sperm head into oocyte cytoplasm at fertilization ultimately leads to the activation of oocyte mechanism including the completion of the meiotic cell cycle, pronuclear development and anti-polyspermy defense.