Complement-inhibiting activity of human seminal plasma and semen quality

Transcriptomic analysis of the seminal vesicle response to the reproductive toxicant acrylamide

BACKGROUND

The seminal vesicles synthesise bioactive factors that support gamete function, modulate the female reproductive tract to promote implantation, and influence developmental programming of offspring phenotype. Despite the significance of the seminal vesicles in reproduction, their biology remains poorly defined. Here, to advance understanding of seminal vesicle biology, we analyse the mouse seminal vesicle transcriptome under normal physiological conditions and in response to acute exposure to the reproductive toxicant acrylamide. Mice were administered acrylamide (25 mg/kg bw/day) or vehicle control daily for five consecutive days prior to collecting seminal vesicle tissue 72 h following the final injection.

RESULTS

A total of 15,304 genes were identified in the seminal vesicles with those encoding secreted proteins amongst the most abundant. In addition to reproductive hormone pathways, functional annotation of the seminal vesicle transcriptome identified cell proliferation, protein synthesis, and cellular death and survival pathways as prominent biological processes. Administration of acrylamide elicited 70 differentially regulated (fold-change ≥1.5 or ≤ 0.67) genes, several of which were orthogonally validated using quantitative PCR. Pathways that initiate gene and protein synthesis to promote cellular survival were prominent amongst the dysregulated pathways. Inflammation was also a key transcriptomic response to acrylamide, with the cytokine, Colony stimulating factor 2 (Csf2) identified as a top-ranked upstream driver and inflammatory mediator associated with recovery of homeostasis. Early growth response (Egr1), C-C motif chemokine ligand 8 (Ccl8), and Collagen, type V, alpha 1 (Col5a1) were also identified amongst the dysregulated genes. Additionally, acrylamide treatment led to subtle changes in the expression of genes that encode proteins secreted by the seminal vesicle, including the complement regulator, Complement factor b (Cfb).

CONCLUSIONS

These data add to emerging evidence demonstrating that the seminal vesicles, like other male reproductive tract tissues, are sensitive to environmental insults, and respond in a manner with potential to exert impact on fetal development and later offspring health.

Molecular Diversification of the Seminal Fluid Proteome in a Recently Diverged Passerine Species Pair

Seminal fluid proteins (SFPs) mediate an array of postmating reproductive processes that influence fertilization and fertility. As such, it is widely held that SFPs may contribute to postmating, prezygotic reproductive barriers between closely related taxa. We investigated seminal fluid (SF) diversification in a recently diverged passerine species pair (Passer domesticus and Passer hispaniolensis) using a combination of proteomic and comparative evolutionary genomic approaches. First, we characterized and compared the SF proteome of the two species, revealing consistencies with known aspects of SFP biology and function in other taxa, including the presence and diversification of proteins involved in immunity and sperm maturation. Second, using whole-genome resequencing data, we assessed patterns of genomic differentiation between house and Spanish sparrows. These analyses detected divergent selection on immunity-related SF genes and positive selective sweeps in regions containing a number of SF genes that also exhibited protein abundance diversification between species. Finally, we analyzed the molecular evolution of SFPs across 11 passerine species and found a significantly higher rate of positive selection in SFPs compared with the rest of the genome, as well as significant enrichments for functional pathways related to immunity in the set of positively selected SF genes. Our results suggest that selection on immunity pathways is an important determinant of passerine SF composition and evolution. Assessing the role of immunity genes in speciation in other recently diverged taxa should be prioritized given the potential role for immunity-related proteins in reproductive incompatibilities in Passer sparrows.

Effects of increased scrotal temperature on semen quality and seminal plasma proteins in Brahman bulls

Environmental temperature has effects on sperm quality with differences in susceptibility between cattle subspecies and breeds, but very little is known about the seminal plasma protein (SPP) changes resulting from testicular heat stress. Scrotal insulation (SI) for 48 hr was applied to Brahman (Bos indicus) bulls. Semen was collected at 3-day intervals from before, until 74 days post-SI. The changes in sperm morphology and motility following SI were comparable to previously reported and differences were detected in measures of sperm chromatin conformation as early as 8 days post-SI. New proteins spots, in the SPP two-dimensional (2-D) gels, were apparent when comparing pre-SI with 74 days post-SI, and SPP identified as associated with mechanisms of cellular repair and protection. Similar trends between 2-D gel and Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS) data was observed, with SWATH-MS able to quantify individual SPP that otherwise were not resolved on 2-D gel. The SPP assessment at peak sperm damage (21-24 days) showed a significant difference in 29 SPP (adjusted p < .05), and identified six proteins with change in abundance in the SI group. In conclusion both spermatozoa and SPP composition of bulls are susceptible to temperature change incurred by SI, and SPP markers for testicular heat insults may be detected.

Proteomic Signatures Reveal Differences in Stress Response, Antioxidant Defense and Proteasomal Activity in Fertile Men with High Seminal ROS Levels

Elevated levels of reactive oxygen species (ROS) are a major cause of male infertility. However, some men with high seminal ROS levels are still fertile. The main objective of this study was to understand the molecular mechanism(s) responsible for the preservation of fertility in those men. Semen samples from fertile men were divided into two groups: control (n = 10, ROS < 102.2 RLU/s/10⁶ sperm) and ROS+ (n = 10, ROS > 102.2 RLU/s/10⁶ sperm). Proteomic analysis of seminal plasma and spermatozoa was used to identify the differentially expressed proteins (DEPs) between the experimental groups, from which some proteins were validated by Western blot (WB). A total of 44 and 371 DEPs were identified between the study groups in the seminal plasma and spermatozoa, respectively. The identified DEPs were primarily involved in oxidoreductase, endopeptidase inhibitor, and antioxidant activities. We validated by WB the underexpression of NADH:ubiquinone oxidoreductase core subunit S1 (p = 0.01), as well as the overexpression of superoxide dismutase 1 (p = 0.03) and peroxiredoxin 4 (p = 0.04) in spermatozoa of ROS+ group. Our data suggest that fertile men with high ROS levels possess an effective antioxidant defense system that protects sperm proteins, as well as an active proteasomal system for degradation of defective proteins.

The Paternal Contribution to Fetal Tolerance

Recognition of foreign paternal antigens expressed in the semi-allogeneic fetus by maternal immune cells is a requirement for successful pregnancy. However, despite intensive research activity during the last decades, the precise mechanisms contributing to the acceptance of the paternal alloantigens are still puzzling and pregnancy remains a fascinating phenomenon. Moreover, most studies focused on the maternal and fetal contribution to pregnancy success, and relatively little is known about the paternal involvement. In the current review, we address the contribution of paternal-derived factors to fetal-tolerance induction. First, we discuss data suggesting that in both humans and mice, the female body gets prepared for a pregnancy in every cycle, also in regard to male alloantigens delivered at coitus. Then, we provide an overview about factors present in seminal fluid and how these factors influence immune responses in the female reproductive tract. We further discuss ways of paternal alloantigen presentation and identify the immune modulatory properties of seminal fluid-derived factors with a special focus on Treg biology. Finally, we highlight the therapeutic potential of seminal fluid in different clinical applications.

Antisperm antibodies and fertility association

OBJECTIVE

To evaluate the relation between antisperm antibodies (ASA) and human fertility by reviewing the scientific literature of the last 45 years.

METHODS

We carried out a review of scientific literature about antisperm antibodies and infertility published in spanish or english in databases as Pubmed, Medline, Scielo, some books and another gray literature include information related to this review and that is published in the last 45 years.

SUMMARY OF EVIDENCE

Infertile couples suffer infertility by immunological mechanisms mainly by the presence of antisperm antibodies ASA in blood, semen or cervicovaginal secretions; the formation of ASA in men and women may be associated with disturbance in immunomodulatory mechanisms that result in functional impairment of sperm and thus its inability to fertilize the oocyte.

CONCLUSION

Immunological infertility caused by ASA is the result of interference of these antibodies in various stages of fertilization process, inhibiting the ability of interaction between sperm and oocyte.

Factor H in porcine seminal plasma protects sperm against complement attack in genital tracts

We found that factor H (FH) exists in porcine seminal plasma. Purified FH strongly inhibited serum alternative pathway complement activation against lipopolysaccharide. The molecular weight, pI, and heparin-binding activity of the purified protein were different from those of purified FH from porcine serum. The complement regulatory activity of seminal plasma FH was approximately 2-fold stronger than that of serum FH. Treatment of purified serum FH with sialidase and N-glycosidase F gave almost the same results as those of seminal plasma FH. The deletion of sialic acid from the carbohydrate chains of both FHs contributed to heparin-binding and complement regulatory activities. Results of reverse transcriptase-PCR, Western blot analysis, and immunohistochemistry showed that seminal plasma FH is mainly secreted from epithelial cells of the seminal vesicle in male genital tracts. FH was also detected in the outer acrosomal region of ejaculated sperm by immunofluorescence staining, and found that the purified FH from the sperm membrane has the same complement regulatory activity as that of seminal plasma FH. The ejaculated sperm possessing FH in the outer acrosomal region considerably evaded complement attack. We also found that there is strong complement activity in fluids from female genital tract ducts. These findings indicate that FH bound to the outer acrosomal region and soluble FH play important roles in protecting sperm against complement attack in male and female genital tracts.

Sperm-zona pellucida interaction and immunological infertility

Immune reactions against gametes appear to be physiologically important for the maintenance of homeostasis in reproduction. In contrast, aberration of the immune homeostasis might give rise to 'immunological infertility'. Antisperm antibodies cause infertility by blocking fertilization. The mechanism can be explained as inhibiting the acrosome reaction of sperm by their blocking effect on capacitation through inhibiting an increase of fluidity of the sperm membrane. Autoantibodies against zona pellucida also cause infertility by blocking sperm-zona pellucida interaction, though the definitive mechanism has not been elucidated. Pretreatment of spermatozoa with D-mannnose completely inhibited sperm penetration through, but not binding to, the zona pellucida. Furthermore, very rapid kinetics between sperm extracts and D-mannnose by a BIAcore apparatus suggest that a D-mannose ligand of the sperm surface is easy to bind to and dissociate from a D-mannose residue in the sperm receptor site on the zona pellucida. Thus, D-mannnose on the human zona pellucida might be an essential molecule acting as a second sperm receptor, through which sperm penetrate into the zona pellucida. Because these antibodies appear to not cause any deleterious clinical symptoms, sperm and zona pellucida antigens are promising candidates in the development of an immunocontraceptive. (Reprod Med Biol 2006; 5: 95-104).

Sperm-zona pellucida interaction and immunological infertility

Immune reactions against gametes appear to be physiologically important for the maintenance of homeostasis in reproduction. In contrast, aberration of the immune homeostasis might give rise to 'immunological infertility'. Antisperm antibodies cause infertility by blocking fertilization. The mechanism can be explained as inhibiting the acrosome reaction of sperm by their blocking effect on capacitation through inhibiting an increase of fluidity of the sperm membrane. Autoantibodies against zona pellucida also cause infertility by blocking sperm-zona pellucida interaction, though the definitive mechanism has not been elucidated. Pretreatment of spermatozoa with D-mannnose completely inhibited sperm penetration through, but not binding to, the zona pellucida. Furthermore, very rapid kinetics between sperm extracts and D-mannnose by a BIAcore apparatus suggest that a D-mannose ligand of the sperm surface is easy to bind to and dissociate from a D-mannose residue in the sperm receptor site on the zona pellucida. Thus, D-mannnose on the human zona pellucida might be an essential molecule acting as a second sperm receptor, through which sperm penetrate into the zona pellucida. Because these antibodies appear to not cause any deleterious clinical symptoms, sperm and zona pellucida antigens are promising candidates in the development of an immunocontraceptive. (Reprod Med Biol 2006; 5: 95-104).

Complement and complement regulators in the male reproductive system

Spermatozoa are almost unique among cells in that they must survive transplantation into a foreign host in order to perform their physiological role. The biggest hurdle to overcome is innate immune defence that will target the invaders in the female genital tract. Complement is a major player in innate immunity and is present in the female genital tract. Spermatozoa must therefore evade complement attack if they are to reach their goal. Complement evasion is achieved by the presence of complement regulators both in seminal plasma and on the spermatozoa. Here we discuss the parts played by complement and complement regulators in permitting spermatozoa to survive long enough to reach the oocyte, in clearance of the excess spermatozoa that have outlived their usefulness and in aiding activation of spermatozoa to engage the oocyte. In particular, we focus on the unique distribution patterns of complement regulators on spermatozoa, patterns that strongly suggest roles in spermatozoal development and oocyte binding. An understanding of these roles will inform studies of their contribution to fertility and infertility in man.

Asthenozoospermia: analysis of a large population

Spermatozoa travel a long distance to meet and fertilize the oocyte, so sperm motility is a requisite for normal fertilization. Asthenozoospermia, or low sperm motility, is a common cause of human male infertility. This is a retrospective study (1992-1999) to document the prevalence of this pathology in infertile men and to clarify the probable factors associated to its etiology. The prevalence was 18.71% for asthenozoospermia and 63.13% for asthenozoospermia associated with oligo- and/or teratozoo-spermia; thus, 81.84% of the studied samples had altered motility. Leukocytospermia, the ratio of germ cells/sperm, anti-sperm antibodies, consistency, biochemical markers of accessory sex glands, and sperm response after swim-up were studied in normospermic (N), asthenozoospermic (A), and combined asthenozoospermic (C) samples. No significant difference was found in the frequency of leukocytospermia among groups. The rate of germ cells/(spermatozoa + germ cells) between C and N (p < .01) and C and A (p < .01) was statistically different, while no difference was found on comparing N and A. MAR-test over 40% was found in 6% of the A samples and 7.6% of the C, while no positive values were observed in the N group. The percentage of hyperviscous samples was higher in the low sperm motility samples than in the normal group. Data on concentration of the biochemical markers seem to be decreased in asthenozoospermia. Pure and combined asthenozoo-spermia showed different behavior in sperm recovery after swim-up. Two different asthenozoospermias could be defined: the pure one where sperm environment is involved (immunological factor, hyperviscosity, and secretory gland function) and the combined, where the testis is comprised.

Alterations of branching and differential expression of sialic acid on alpha-1-acid glycoprotein in human seminal plasma

BACKGROUND

The degree of branching and types of fucosylation of glycans on alpha(1)-acid glycoprotein (AGP) have been found to be associated with alpha(1)-acid glycoprotein concentrations in human seminal plasma. The glycosylation pattern of alpha(1)-acid glycoprotein in seminal plasma obtained from men living in infertile couples can undergo alterations in relation to sperm analysis and/or alpha(1)-acid glycoprotein concentrations.

METHODS

The glycosylation of alpha(1)-acid glycoprotein was studied upon the reactivity with specific lectins by crossed affinity immunoelectrophoresis (concanavalin A), and by glycoprotein lectin immunosorbent assay (Maackia amurensis and Sambucus nigra lectins), as well as high pH anion-exchange chromatography with pulsed amperometric detection.

RESULTS

Nonsignificant differences in alpha(1)-acid glycoprotein glycan branching and degree of its sialylation were observed among the AGP derived from seminal plasmas in relation to spermiogram and sperm morphology. However, significant concentration-dependent differences were found in extent of branching and type of sialylation.

CONCLUSIONS

The presence in seminal plasma of high concentrations of aberrantly glycosylated AGP molecules might be indicative for a chronic inflammatory condition in the reproductive tract, and can be used as additional tool to subdivide the seminal plasmas of men living in infertile couples.

High level of alpha1-acid glycoprotein in human seminal plasma is associated with high branching and expression of Lewis(a) groups on its glycans: supporting evidence for a prostatic origin

BACKGROUND

Changes in concentration of seminal plasma alpha(1)-acid glycoprotein (AGP) have been studied in detail before. However, the source of high levels of AGP as well as the glycosylation of seminal plasma AGP has not been elucidated yet.

METHODS

The glycosylation of AGP was studied by crossed affinity immunoelectrophoresis using fucose-specific lectins and immunostaining. Glycan structure and monosaccharide analyses were performed by high pH anion exchange chromatography with pulsed amperometric detection. Fucosyltransferases were analyzed for activity and their substrate specificity was determined.

RESULTS

Two types of fucosylation were detected; Lewis(x) and Lewis(a). Lewis(a) groups were only present on AGP of individuals with a high concentration and were completely absent when the AGP concentration in seminal plasma was low. Lewis(a) expression coincides with a higher degree of branching of the glycans and a relative increased alpha4-fucosyltransferase activity. The molecular weight of all seminal plasma AGP was slightly higher than of blood plasma AGP (approx. 47 vs. 41-43 kDa).

CONCLUSIONS

The results indicate that AGP in seminal fluid most likely originates from the prostate and that it is either alpha3- or alpha4-fucosylated.