Role of cytokines and proto-oncogenes in sperm cell function: relevance to immunologic infertility

Surfactant protein D regulates murine testicular immune milieu and sperm functions

PROBLEM

Surfactant protein D (SP-D), a pattern recognition protein that regulates inflammation and immune homoeostasis, is expressed by testicular germ cells under the influence of testosterone. This study investigates the role of SP-D in testicular immune privilege and sperm functions.

METHOD OF STUDY

Testicular levels of cytokines and immunoregulatory molecules were evaluated in lipopolysaccharide (LPS)-challenged SP-D gene knockout mice (SP-D^-/- ). Further, sperm functions were assessed by computer-assisted sperm analyser (CASA) and in vitro capacitation. The effect of a recombinant fragment of human SP-D (rhSP-D) on LPS-induced testicular inflammation and sperm motility was assessed in wild-type (WT) mice.

RESULT

Endogenous absence of SP-D led to significantly increased testicular levels of immunosuppressive molecules, viz. serpina3, TGF-β1 and IL-10, and reduced levels of immune cell activation markers, CD86, IL-2 and ITGAX. These compensatory mechanisms resulted in markedly blunted levels of TNF-α, IL-12p40, MIP-1α, G-CSF and IL-6 in response to LPS challenge. Notably, exogenous supplementation of rhSP-D salvaged the WT mice from LPS-induced pro-inflammatory immune response and impairment of sperm motility by upregulating the levels of TGF-β1 and IL-10.

CONCLUSION

The study highlights the involvement of SP-D in maintenance of testicular immune privilege and its indirect contribution to male fertility.

Inhibition of in vitro gamete adhesion and in vivo fertility in mice by immunization with a synthetic peptide

PROBLEM

To evaluate the contraceptive ability of a synthetic peptide in in vitro and in vivo fertility in the mouse.

METHOD OF STUDY

A synthetic peptide segment: GELRERAPGQGTNG (SP) was used to immunize female B6CF1 (C57BL/6 x BALB/c) mice. A peptide with an amino acid sequence QQPLSIQQHERG (p2control) was used as control. Anti-SP and anti-p2control antisera were used to evaluate sperm function inhibition in vitro. Fertility of immunized mice was determined by microscopic evaluation of the number and state of preimplantation embryos (8-16 cell stage).

RESULTS

In the mouse, anti-SP antisera recognized surface antigens in the acrosome region of mature and capacitated sperm. Anti-SP antisera inhibited in vitro sperm binding to zona pellucida. In vivo, immune response against SP in Freund's adjuvant resulted in a significant increase (P < 0.01) in the number of dead embryos and eggs (a mean of 66%, in contrast with < 25% in control mice). Fertility inhibition in vivo and in vitro was not observed when the p2control peptide was used in the immunizations.

CONCLUSIONS

These results would suggest that the SP sequence is involved in gamete adhesion, and an antifertility vaccine against the SP peptide segment could be feasible.

Infliximab may reverse the toxic effects induced by tumor necrosis factor alpha in human spermatozoa: an in vitro model

OBJECTIVE

To examine the toxic effects of tumor necrosis factor alpha (TNF-alpha) on ejaculated spermatozoa and evaluate the ability of infliximab to reverse these effects.

DESIGN

Prospective controlled study.

SETTING

Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Thirty-one healthy sperm donors.

INTERVENTION(S)

Exposure of human spermatozoa to varying concentrations of TNF-alpha (100, 300, 400, 500 pg/mL, and 2.5 microg/mL) and infliximab (400 microg/mL).

MAIN OUTCOME MEASURE(S)

Sperm motility, functional integrity of plasma membrane, and DNA fragmentation.

RESULT(S)

Spermatozoa quality declined following incubation with TNF-alpha in a dose-dependent and time-dependent manner. Sperm motility and membrane integrity were higher in the samples incubated with TNF-alpha plus infliximab than in the samples treated with TNF-alpha only. These parameters improved significantly and were comparable with both controls and sperm incubated with infliximab alone. Similarly, the percentage of spermatozoa with DNA fragmentation improved significantly following incubation with TNF-alpha plus infliximab and again was comparable with both controls and sperm incubated with infliximab alone.

CONCLUSION(S)

Spermatozoa may be exposed to abnormal levels of TNF-alpha in the male reproductive tract or during their passage into the female reproductive tract (in cases of endometriosis). Exposing spermatozoa to pathological concentrations of TNF-alpha can result in significant loss of their functional and genomic integrity. Infliximab could potentially be used to help treat female infertility caused by endometriosis in those with elevated levels of TNF-alpha in their peritoneal fluid.

Role of tyrosine phosphorylation in sperm capacitation / acrosome reaction

Capacitation is an important physiological pre-requisite before the sperm cell can acrosome react and fertilize the oocyte. Recent reports from several laboratories have amply documented that the protein phosphorylation especially at tyrosine residues is one of the most important events that occur during capacitation. In this article, we have reviewed the data from our and other laboratories, and have constructed a heuristic model for the mechanisms and molecules involved in capacitation/acrosome reaction.

Role of genitourinary inflammation in infertility: synergistic effect of lipopolysaccharide and interferon-gamma on human spermatozoa

Pro-inflammatory cytokines are elevated in the semen of patients with genitourinary inflammation (GUI). Whether this increase in cytokines in GUI patients plays any critical role in male factor infertility is not clear. The present study investigated the in vitro effects of two important pro-inflammatory cytokines, lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), on sperm motility, viability, membrane integrity and motion parameters. Washed spermatozoa from healthy donors were incubated with LPS (0.1 mg/mL) or IFN-gamma (0.1 mg/mL) alone or in combination. Sperm motility, viability, membrane integrity and computer-assisted motion were evaluated at various time intervals (0, 30, 60 and 180 min) after treatment. Sperm membrane integrity was analysed using the hypo-osmotic swelling test (HOST). LPS and IFN-gamma individually did not alter sperm viability or motility, but their combination showed a significant time-dependent decrease (p < 0.05) in sperm motility, viability and membrane integrity. Sperm motion parameters (straight-line velocity, curvilinear velocity, mean linearity, or amplitude of lateral head displacement) were not affected by LPS or IFN-gamma at the concentrations used in this study. These data suggest that the combination of LPS and IFN-gamma is detrimental to human spermatozoa and may contribute to male factor infertility in patients with chronic GUI.

Expression of alpha and gamma interferon receptors in the sperm cell

The present study was conducted to examine whether or not the sperm cell has the expression of receptors for interferon (IFN) -alpha and -gamma. This was investigated using specific antibodies. Antibody to IFN-alpha receptor reacted with the acrosomal and tail regions of the murine sperm cell in the indirect immunofluorescence technique (IFT) and immunoscanning electron microscopic procedure (ISEP). In the immunoprecipitation and Western blot procedures, this antibody specifically recognized a protein band of approximately 100 kD, which corresponds to the molecular weight of IFN-alpha receptor present in other cell types. Antibody to IFN-gamma receptor specifically reacted with the posterior head, midpiece, and tail regions of sperm cell in IFT and ISEP, and recognized a band of approximately 85 kD in the immunoprecipitation and Western blot procedures, corresponding to the IFN-alpha receptor. Similar bands of approximately 100 kD and approximately 85 kD molecular identities were also detected in the testes extracts and sperm extracts of other mammalian species namely human, rabbit, and pig, the species tested. These findings indicate that the mammalian sperm cell has expression of IFN-alpha and IFN-gamma receptors, which seem to develop during spermatogenesis in the testes. These findings may have implications in male infertility and antisperm contraceptive vaccine development.

Seminal immune response in infertile men with leukocytospermia: effect on antioxidant activity

OBJECTIVE

To investigate the incidence of leukocytospermia and relation to T helper cytokines, tumor necrosis factor alpha (TNFalpha) and interleukin-4 (IL-4), antisperm antibodies and antioxidant activity.

DESIGN

Semen samples from 176 infertile men and 24 fertile controls were investigated.

METHODOLOGY

The protocol included tubal patency test, hysterosalpingography and laparoscopy and dye test and ovulation through mid-luteal phase progesterone for the wives. The husbands had semen analysis, cytomorphology evaluation and semen culture. Seminal TNFalpha and IL-4, antisperm antibodies, total antioxidant activity, superoxide dismutase and zinc were determined.

RESULTS

Leukocytospermia occurred in 44.3% of the infertile men compared to 12.5% of the fertile men (P<0.01). Thirty-six (20.5%) men had pathogenic bacterial organisms which constituted 46.2% of those with leukocytospermia. Sperm parameters were worse with leukocytospermia in terms of sperm count (P<0.01), total motility progressive motility (P<0.01), morphology, asthenozoospermia, sperm membrane integrity and antisperm antibodies. TNFalpha and IL-4 had an inverse relationship; the expression of TNFalpha was higher with leukocytospermia and bacteriospermia (P<0.001), while IL-4 was higher in fertile controls (P<0.005). Incidence of antisperm antibodies was higher with leukocytospermia. Total antioxidant activity, superoxide dismutase and zinc were lower with leukocytospermia.

CONCLUSION

Leukocytospermia impairs sperm function through reduced antioxidant activity and enhanced T helper 1 modulation.

Potential contraceptive use of epididymal proteins: immunization of male rats with epididymal protein DE inhibits sperm fusion ability

Rat epididymal protein DE associates with the sperm surface during maturation and participates in sperm-egg fusion. Immunization of male rats with DE raised specific antibodies and produced a significant reduction in the animals' fertility. The present study focused on determining the in vivo mechanism involved in fertility inhibition. Wistar males were injected with DE, and antibody levels and animal fertility were evaluated. Results revealed an association between the two parameters, since animals with absorbance values lower than 0.5 in ELISA presented high fertility rates (66%, 100%) while those with absorbance values higher than 0.5 exhibited the lowest fertility rates (0%, 33%). Histological studies showed no evidence of orchitis, epididymitis, or vasitis in DE-immunized animals. ELISA results revealed the presence of anti-DE antibodies in epididymal and vas deferential fluids. Indirect immunofluorescence and ELISA experiments indicated that these antibodies would not interfere with the synthesis or secretion of DE or with its association with the sperm surface. Finally, while epididymal sperm recovered from DE-immunized animals presented no changes in motility, viability, or ability to undergo capacitation and acrosome reaction, they exhibited a significant decrease in their ability to fuse with zona-free eggs, with no effect on their ability to bind to the oolemma. Together these results indicate that immunization of male rats with epididymal protein DE specifically interferes with the sperm fertilizing ability, supporting the use of epididymal proteins for contraceptive vaccine development.

T-helper 2 type cytokine and soluble interleukin-2 receptor levels in seminal plasma of infertile men

PROBLEM

The role of cell-mediated immunity (CMI) in unexplained male infertility and impaired sperm function has been explored.

METHOD OF STUDY

The presence of cytokines, namely, interleukin-4 (IL-4), interleukin-6 (IL-6), and the soluble interleukin-2 receptor (SIL-2R), was investigated in seminal plasma of 18 fertile and 20 infertile subjects, using specific enzyme-linked immunoadsorbent assays.

RESULTS

IL-4 was not detected. SIL-2R was detected, but the concentration difference between the fertile and infertile group was not significant. IL-6 was detected with significantly higher levels in the infertile group compared to the fertile group. IL-6 levels in seminal plasma correlated positively with leukocyte count and negatively with sperm count, motility, and morphology.

CONCLUSIONS

These findings show: a) a lack of IL-4 in seminal plasma; b) similar SIL-2R levels in fertile and infertile seminal plasma; c) increased IL-6 secretion in seminal plasma of infertile subjects; and d) specific correlations of IL-6 with the main semen parameters.

Expression of tumor necrosis factor-alpha and its receptors type I and type II in human oocytes

The present study was conducted to examine the expression of tumor necrosis factor-alpha (TNF-alpha) and its receptors (types I and II, designated TNFR-I and TNFR-II, respectively) in human oocytes and cumulus cells at the mRNA and protein levels. mRNA expression was investigated using a reverse transcriptase-polymerase chain reaction (PCR)/Southern hybridization procedure. DNA-free RNA was isolated from the oocytes/cumulus cells, reverse-transcribed, and PCR-amplified using specific oligonucleotide primers based upon genomic/cDNA sequences. The expected bands of 303 bp and 513 bp were observed in oocytes and cumulus cells using primers based on genomic/cDNA sequences of TNF-alpha and TNFR-II, respectively, that hybridized with specific cDNA probes in Southern blot hybridization procedure. The expected band of 368 bp was not observed in oocytes and cumulus cells using primers based on the TNFR-I cDNA sequence. Similar results were observed for expression at the protein level, as seen by the immunoreactivity of the specific antibodies with the paraformaldehyde-fixed oocytes and cumulus cells in the indirect immunofluorescence technique (IFT). These results indicate that human oocytes and cumulus cells express TNF-alpha and its receptor type II (TNFR-II), and not type I (TNFR-I), both at the mRNA and protein levels. These findings provide further evidence and substantiate the proposed physiologic role of TNF-alpha in ovarian function, and may lead to clinical applications in in vitro fertilization programs and in diagnosis and treatment of infertility in women, especially in cases attributed to ovarian dysfunction.

Effects of products of activated immune cells and recombinant cytokines on spontaneous and ionophore-induced acrosome reaction

PROBLEM

The purpose of this study was to examine whether the products of activated immune cells influence spontaneous and ionophore-induced sperm acrosome reaction.

METHOD

The spontaneous and ionophore-induced acrosome reaction were evaluated by staining with fluorescein isothiocyanate (FITC) Pisum sativam agglutinin after incubation in capacitating media supplemented with either supernatants from Con-A activated leukocyte cultures or human recombinant (r) IL-1 beta, TNF-alpha, and INF-gamma.

RESULTS

The supernatants from Con A-activated peripheral blood leukocyte cultures at 1:1 and 1:10 dilution significantly increased the rate of spontaneous acrosome reaction (P < 0.001 and P < 0.01). Along with displayed abnormally elevated levels of spontaneous acrosome loss, sperm cells showed an insufficient ability to undergo acrosome reaction in response to the ionophore treatment. Recombinant IL-1 beta at increasing concentrations from 30 to 3 x 10(4) U/ml did not have an effect on spontaneous and ionophore-induced acrosome reaction. In contrast, spermatozoa that underwent capacitation in media with 7 x 10(3), 7 x 10(4), and 7 x 10(5) U/ml of rINF-gamma showed a significant increase in spontaneous and induced acrosome reaction compared to the control (P < 0.001). Recombinant TNF-alpha at concentrations of 3.5 x 10(3) U/ml and 3.5 x 10(4) U/ml significantly inhibited ionophore-induced acrosome reaction (P < 0.001). Both rINF-gamma and rTNF-alpha together revealed an effect on the acrosome reaction similar to Con-A generated supernatants (1:1 and 1:10 dilution) only at the highest concentrations.

CONCLUSIONS

Some cases of infertility may result from a defective acrosome reaction (premature acrosome loss or insufficient acrosome response to the stimulants) caused by products of activated lymphocytes and macrophages that are released into the male and female reproductive tracts.

Protein tyrosine phosphorylation and signal transduction during capacitation-acrosome reaction and zona pellucida binding in human sperm

During capacitation and acrosome reaction of human sperm, 7-14 proteins are phosphorylated, and two of these proteins (95 and 51 kD) are phosphorylated at tyrosine resides. The sperm proteins that bind ZP3 in humans have molecular identities of 95, 63, 51 (FA-1 antigen), and 14-18 kD, respectively. Three of these molecules, 95-, 51-, and 14-18-kD proteins, undergo tyrosine phosphorylation, and 51 kD (FA-1 antigen) also undergoes autophosphorylation. Many of the sperm proteins that participate in ZP binding are also involved in capacitation/acrosome reaction. These findings indicate a vital role of protein tyrosine phosphorylation and tyrosine receptor kinases in sperm capacitation, acrosome reaction, and ZP binding. Since tyrosine phosphorylation is the primary, or even exclusive, indication of signal transduction, it would appear that a signal transduction pathway is involved in these processes. However, the exact mechanism requires further study.

Interleukins-6 and -8 levels in sera and cervical mucus of fertile, idiopathic infertile, and immunoinfertile women: implication in infertility

PROBLEM

The purpose of this study was to investigate the levels of interleukin-6 and -8 (IL-6 and IL-8) in sera and cervical mucus of infertile (idiopathic and immunoinfertile) women and to compare the levels with those in age-matched normally cycling fertile women.

METHODS

Levels of IL-6 and IL-8 were measured in the sera and cervical mucus of fertile and infertile women by the enzyme-linked immunosorbent assay (ELISA). A non-parametric Mann-Whitney test was used to evaluate significance between the means. Linear regression analysis of IL-6 and IL-8 concentrations in serum versus cervical mucus and with antisperm antibody titers was performed by condition as well as all groups together. P < 0.05 was considered significant.

RESULTS

Both IL-6 and IL-8 were detected in sera and cervical mucus of fertile as well as infertile groups. Although serum levels of IL-6 and IL-8 were significantly different between fertile and infertile groups, the differences were more pronounced in the cervical mucus samples. Cervical mucus of idiopathic and immunoinfertile women demonstrated significantly (P = 0.002 to < 0.0001) greater concentrations of IL-6 and IL-8 compared to fertile controls. In general, there was no significant correlation between the serum and cervical mucus IL-6 and IL-8 levels, whether analyzed by condition or all groups together.

CONCLUSIONS

Elevated levels of IL-6 and IL-8 in cervical mucus of infertile groups may play a role in etiology of idiopathic and immunologic infertility. These findings suggest that the measurements of cytokines (especially IL-6 and IL-8) in cervical mucus may provide a tool for specific diagnosis and possibly treatment of infertility, especially idiopathic infertility.

Disintegration of human spermatozoal membranes in seminal plasma decreases the binding capacity of integrins

The in vitro binding capacity of spermatozoal integrins to matrix components after disintegration of sperm membranes was evaluated. The percentage of spermatozoa with functionally-relevant integrins was determined before and after devitalization of spermatozoa, which were resuspended in seminal plasma or in culture medium. The devitalization was performed by cryoshock or by incubation of spermatozoa with triton X-100 in a concentration ranging from 0.01 to 1.0%. The spermatozoal integrins were detected by the binding of anti-integrin antibodies and flow cytometry and the functional activity was monitored by the binding of the spermatozoa to the matrix components in a cell attachment assay. The seminal plasma decreased the binding of anti-integrin antibodies to the spermatozoal surface and the binding of spermatozoa to ligands and matrix components. respectively. In contrast, the expression of fibronectin and laminin on spermatozoa was increased. Not all spermatozoa, which expressed integrins on their surface bound to the ligands in the cell attachment assay. These results suggest that the detectable integrins only partially exert functional relevance. It can be concluded that the spermatozoa with fragile plasma membranes are more prone to functional inactivation of their integrins by the seminal plasma.

Levels of interferon-gamma and tumor necrosis factor-alpha in sera and cervical mucus of fertile and infertile women: implication in infertility

Concentrations of two immune cytokines, namely interferon-gamma (INF-gamma) and tumor necrosis factor-alpha (TNF-alpha), were determined in the sera and cervical mucus samples of fertile (n = 16), idiopathic infertile (n = 44), and immunoinfertile women (n = 45) to investigate their role, if any, in female infertility. Sera of idiopathic infertile women demonstrated significantly (P < 0.0001) higher levels of INF-gamma compared to those in fertile controls, whether expressed as pg/ml or pg/mg serum protein. Similarly, sera of immunoinfertile women demonstrated significantly (P = 0.0008) higher levels of INF-gamma compared to fertile controls and idiopathic infertile women. Cervical mucus of idiopathic infertile women also demonstrated significantly (P < 0.0001) higher concentrations of INF-gamma compared to those in fertile controls. Cervical mucus of immunoinfertile women demonstrated significantly (P < 0.0001) higher concentrations of INF-gamma compared to those in fertile controls and idiopathic infertile women. INF-gamma levels in serum did not significantly (P > 0.05) correlate (r = 0.12-0.43) with the concentrations in cervical mucus, when all the three groups were compared together. However, when the serum levels were compared with the cervical mucus concentrations by condition, only the idiopathic infertile group showed a significant (P = 0.005) correlation (r = 0.70). Serum levels of TNF-alpha did not differ significantly (P > 0.05) among three groups of women. Cervical mucus concentrations of TNF-alpha, however, varied among groups with levels being significantly (P = 0.04) higher-in idiopathic infertile women compared with fertile controls and in immunoinfertile women significantly (P = 0.0007) higher than in fertile controls as well as idiopathic infertile women. TNF-alpha levels in serum correlated (r = 0.65) significantly (P < 0.001) with the concentrations in cervical mucus when all the three groups were compared together or individually by infertility condition. These findings suggest the involvement of cytokines in infertility, and thus may have potential applications in diagnosis and treatment of female infertility.

Effects of synthetic thymosin-alpha 1 and its analogs on fertilizability of human sperm: search for a biologically active, stable epitope

Thymosin-alpha 1 (T alpha 1) and six T alpha 1 analogs were synthesized to study structure-function relationships and to search for the biologically active and stable epitope(s) that would have clinical application in the treatment of male infertility. Four of these analogs were prepared by modification/substitution of N- and C-terminal amino acids of T alpha 1 peptide, and the other two analogs were fragments having only N-16 amino acids (N-terminal) or C-14 amino acids (C-terminal), respectively, of the T alpha 1 peptide. T alpha 1 and these six analogs were tested for their effects on human sperm penetration rates in the sperm penetration assay (SPA). T alpha 1 significantly (p < .0001) increased the penetration rates in SPA, with the strongest enhancing effect at 0.5 microgram/100 microL concentration. Of the six analogs tested only two, T alpha 1-Gly-NH2 and T alpha 1-C14, retained the enhancing effects in SPA. None of the analogs decreased the penetration rates or affected sperm motility compared to control. The enhancing activity resides primarily in an epitope, the C-terminal 14 amino acids of T alpha 1. However, for maximal effect both N- and C-terminal amino acids (serine and asparagine, respectively) have to be intact and unmodified. The T alpha 1-Gly-NH2 analog that had its C-terminal protected was as potent as the intact T alpha 1 peptide. T alpha 1 and this analog may have clinical applications in treatment of male-factor-mediated infertility.

Enhanced levels of colony stimulating factor-1 (CSF-1) in sera and seminal plasma of antisperm antibody-positive infertile men

This investigation was carried out to examine the levels of CSF-1 in sera and seminal plasma of fertile, immunoinfertile, and male factor-infertile men in order to study the role of CSF-1 in human infertility. Sera, sperm, and seminal plasma were analyzed for antisperm antibodies by the sperm immobilization technique, tray agglutination technique, and immunobead binding technique. Sperm motility and fertilizing capacity were analyzed by sperm motion analysis and sperm penetration assay, respectively. CSF-1 concentration was estimated by the competitive radioimmunoassay. CSF-1 was detected in sera of both fertile and immunoinfertile men (mean +/- SD; fertile men: 52.9 +/- 10.3 pg/mg protein; immunoinfertile: 58.2 +/- 19.5 pg/mg protein; p > .05). CSF-1 was also detected in the seminal plasma of fertile, immunoinfertile, and male factor-infertile men (mean +/- SD; normal fertile men: 1.7 +/- 3.5 ng/mg; immunoinfertile men: 10.9 +/- 15.6 ng/mg; male factor-infertile men: 0.85 +/- 0.25 ng/mg). The levels of CSF-1 were highest in the immunoinfertile men, followed by those in fertile and male factor-infertile men. The average level in immunoinfertile men was significantly different from the average level in fertile or male factor-infertile men (p < .0001). Interestingly, the concentrations of CSF-1 per milliliter of seminal plasma was in general approximately 5 times greater than those in serum. These findings indicate that elevated seminal plasma CSF-1 concentration is correlated with male infertility.

The biologic significance of white blood cells in semen

OBJECTIVE

To analyze the data available on the biologic significance of white blood cells (WBC) in semen of infertility patients.

DATA RESOURCES

The relevant literature was reviewed.

RESULTS

It is not possible to identify reliably WBC by conventional sperm staining techniques. The peroxidase method is sufficient for quantification of granulocytes, but immunocytology is the gold standard for the detection of all WBC populations in semen. Granulocytes are the most prevalent WBC type in semen (50% to 60%), followed by macrophages (20% to 30%) and T-lymphocytes (2% to 5%). The prevalence of leukocytospermia (> 10(6) WBC/mL semen) among male infertility patients is approximately 10% to 20%. There is controversy on the significance of WBC in semen. Whereas some authors did not observe sperm damage in the presence of leukocytospermia, others have found evidence that WBC are significant cofactors of male infertility: [1] seminal WBC numbers were higher in infertility patients than among fertile men; [2] leukocytospermia was associated with decreased sperm numbers and impaired sperm motility; [3] WBC damaged sperm function and hamster ovum penetration in vitro and were important prognostic factors for IVF-ET failure. Because of absence of clinical symptoms, the origin of WBC is difficult to determine. Normally, most WBC appear to originate from the epididymis because vasectomized men show very few WBC in semen. On the other hand, leukocytospermic samples show low citric acid levels, pointing to asymptomatic prostatitis as a source of WBC in semen. Surprisingly, approximately 80% of leukocytospermic samples are microbiologically negative. In some cases Chlamydia trachomatis might have triggered a persistent inflammatory reaction leading to leukocytospermia. Sperm damage by WBC can be mediated by reactive oxygen species, proteases and cytokines. Furthermore, genital tract inflammation facilitates the formation of sperm antibodies. As seminal plasma has strong anti-inflammatory properties and because there is only short contact between sperm and WBC in prostatitis and seminal vesiculitis, inflammations of the epididymis and testis are likely to have the largest impact on sperm.

CONCLUSIONS

There is ample evidence that WBC can affect sperm function. Further studies are needed to define cofactors that increase or decrease the risk of sperm damage by WBC.

Fertilization antigen (FA-1) completely blocks human sperm binding to human zona pellucida: FA-1 antigen may be a sperm receptor for zona pellucida in humans

The effects of purified human sperm fertilization antigen-1 (FA-1), affinity-purified monoclonal Fab' antibody to FA-1, and monoclonal Fab' antibody to phosphotyrosine residues on human sperm-zona interaction were investigated. The purified FA-1 antigen completely blocked sperm binding to zona pellucida (P < 0.0001). Also, the monoclonal Fab' antibodies to FA-1 antigen and phosphotyrosine residues significantly (P < 0.05) reduced sperm-zona pellucidae and the antibodies were preincubated with sperm before insemination and not vice versa. These results suggest that the tyrosine phosphorylation especially of FA-1 antigen has an important role in zona pellucida receptor recognition and binding. These findings also suggest that FA-1 antigen may be the sperm receptor involved in zona pellucida binding in humans.

Molecular identities of human sperm proteins that bind human zona pellucida: nature of sperm-zona interaction, tyrosine kinase activity, and involvement of FA-1

The present study was conducted to investigate the molecular identities, nature of interaction, and tyrosine phosphorylation activity of the sperm-zona pellucida binding proteins in humans. Sperm proteins belonging to four major molecular regions, namely 95, 63, 51, and 14-18 kDa, reacted with zona pellucida proteins in the Western blot and immunoprecipitation procedures. In these procedures, zona pellucida protein that reacted strongest with the sperm proteins belonged to the molecular region of 55 kDa (ZP3), besides weakly reacting proteins in the 110-kDa (ZP1/ZP2) and 14-18-kDa molecular regions. The major forces involved in the sperm-zona protein interactions were of hydrophobic and ionic in nature. Three (95, 51, and 14-18 kDa) of the four molecular regions of sperm proteins that bound to the zona pellucida proteins also seem to involve o-phospho-L-tyrosine residues in their interaction, and these proteins demonstrated the presence of phosphotyrosine residues, and the 51-kDa protein also showed autophosphorylating activity in the in vitro kinase assay. The sperm binding zona protein of 55 kDa also demonstrated autophosphorylating activity. Using specific monoclonal antibody to the well characterized sperm-specific glycoprotein, designated FA-1, and the competitive inhibition in the immunoprecipitation procedure, it was found that the 51 kDa protein is indeed FA-1 antigen. Besides elucidating the molecular nature of the sperm-zona interaction, these antigens will find application in the development of a multivalent contraceptive vaccine, and may also help in specific diagnosis and treatment of infertility mediated through defective gamete (sperm or oocyte) function.

Expression and role of c-myc protooncogene in murine preimplantation embryonic development

PURPOSE

The present study was conducted to investigate the expression and possible role of the c-myc protooncogene in preimplantation embryos by using reverse-transcriptase/polymerase chain reaction (RT-PCR) technique and microinjection of synthetic antisense c-myc oligonucleotide probe, respectively. Total RNA was extracted from oocytes and two cell-, four cell-, early morula-, late morula-, early blastocyst-, and late blastocyst-stage embryos, and cDNA was constructed using MMLV reverse transcriptase. Sense primer (P1) and antisense primer (P2) used were based on the c-myc gene sequence bp 1609-1629 and bp 3279-3299, respectively, that span a 1.37-kb intron. PCR-amplified products of cDNA from oocyte-, two cell-, four cell-, early and late morula-, and blastocyst-stage embryos demonstrated the expected 313-bp product in Southern blot hybridization using a c-myc specific DNA probe, with an indication of lower levels in oocytes and early morulae.

RESULTS

Cytoplasmic injection of the antisense c-myc oligonucleotide probe (P2) and not the sense probe (P1) into pronuclear-stage zygotes caused a significant (P = 0.02 to 0.0001) inhibition of development to blastocysts in a concentration-dependent manner, with a maximal inhibition at the first cleavage of zygotes to two cell-stage embryos. There was no effect on the P2 antisense injection on pronucleus formation.

CONCLUSION

These results indicate that the c-myc protooncogene is expressed in preimplantation embryos and may have an essential role in normal embryogenesis in mice.