Presence of membrane and soluble forms of Fas ligand and of matrilysin (MMP-7) activity in normal and abnormal human semen

Expression of proapoptotic receptors Fas/Fas-L on sperm cells and levels of their soluble forms in seminal fluid from patients with varicocele

Varicocele is a condition in which the pampiniform venous plexus in the scrotum dilates abnormally during puberty, affecting testicular growth and semen parameters, and is thought to be a major cause of male infertility. The findings of researches on the presence of the Fas system in sperm are controversial. As the main triggers of apoptosis in the semen of patients with varicocele, in this study, we examined the expression of Fas/Fas-L on sperm cells and also the levels of their soluble forms in seminal plasma. Semen samples were taken from 45 patients with varicocele (study group) and 45 healthy subjects without varicocele (control group) after 3-5 days of ejaculatory abstinence. Flow cytometry was used to examine the expression of Fas and Fas ligand (Fas-L) on Sperm cells. Furthermore, soluble Fas (sFas) and soluble Fas-Ligand (sFas-L) levels in the seminal fluid were determined using an ELISA (enzyme-linked immunosorbent assay). The presence of Fas and Fas-L proteins on the sperm ejaculation surface was not found in the patients with varicocele or the control groups. However, in the case group (3.32 ± 0.31 ng/mL), sFas seminal concentrations were slightly lower than in the control group (5.50 ± 0.36 ng/mL) (p < 0.001). In varicocele patients, there was a strong negative association between seminal sFas and sperm motility. Apoptosis effects through this system on key sperm parameters were not found based on our findings. In varicocele, a reduction in sperm count and motility does not seem to be due to Fas-related mechanisms, but rather to other mechanisms.

Restraint stress of male mice induces apoptosis in spermatozoa and spermatogenic cells: role of the FasL/Fas system†

The mechanisms by which psychological stress impairs semen quality are largely unknown. By using a restraint-stressed mouse model, we studied the role of the FasL/Fas system in psychological stress-induced apoptosis of spermatozoa and spermatogenic cells. Male mice were restrained for 48 h before examination for sperm fertilizing potential and for apoptosis and FasL/Fas expression in spermatozoa, spermatogenetic cells/seminiferous tubules, and caudae epididymides. The results showed that the male restraint reduced motility, fertilization rates, and mitochondrial membrane potential while increasing apoptosis and Fas expression in spermatozoa. Restraint also facilitated apoptosis and FasL/Fas expression in spermatogenic cells/seminiferous tubules and caudae epididymides. The restraint-induced apoptosis in spermatozoa and spermatogenic cells was significantly ameliorated in gld mice that harbor a loss-of-function mutation in FasL. However, incubation with FasL did not affect sperm motility and apoptosis, while incubation with tumor necrosis factor (TNF)-α did. The epididymis of the gld mice produced significantly less TNF-α and TNF-related apoptosis-inducing ligand (TRAIL) than that of wild-type mice did after male restraint. Thus, the results confirmed that the FasL/Fas system played an important role in the psychological stress-induced apoptosis of spermatozoa and spermatogenic cells and that FasL triggered sperm apoptosis in epididymis dependently through promoting TNF-α and TRAIL secretion.

Semen levels of matrix metalloproteinase (MMP) and tissue inhibitor of metallorproteinases (TIMP) protein families members in men with high and low sperm DNA fragmentation

Matrix Metalloproteinases (MMPs) and their regulators – Tissue Inhibitors of Matrix Metalloproteinases (TIMPs) – participate in extracellular matrix remodeling, fibrosis, and semen liquefaction, as well as to inflammatory activity. Seminal plasma has been shown to contain MMPs (MMP-2 and MMP-9) and TIMPs (TIMP-1 and TIMP-2). Also, a link between MMPs gene expression and excessive reactive oxygen species (ROS) has been established. In semen, ROS are associated with altered sperm function and increased DNA fragmentation. In this study, it is hypothesized that seminal MMPs and TIMPs levels are associated with sperm DNA fragmentation due to the fact that MMPs have been associated with semen quality. We also hypothesized that these proteins could predict DNA fragmentation status in sperm. Therefore, this study set out to verify if sperm DNA fragmentation levels relate to seminal levels of members of the MMP and TIMP protein families. The High sperm DNA fragmentation group presented lower seminal plasma levels of MMP-2, MMP-7, TIMP-1, TIMP-2 and TIMP-4 when compared to Low sperm DNA fragmentation group. Also, samples in the high sperm DNA fragmentation group presented higher acrosome integrity and lower mitochondrial activity levels when compared to low sperm DNA fragmentation samples. In the logistic regression analysis, MMP-2, MMP-7, and TIMP-4 classified samples as low and high sperm DNA fragmentation, with an overall model fit of 74.5%. Results from this study may demonstrate a specific inflammatory mechanism in samples with high sperm DNA fragmentation. This, in turn, can lead to the development of new studies regarding this mechanism and, in the future, create an opportunity to treat these patients for sperm DNA fragmentation by treating inflammatory seminal activity.

In vivo treatments with fulvestrant and anastrozole differentially affect gene expression in the rat efferent ductules

Estrogen plays a key role in maintaining the morphology and function of the efferent ductules. We previously demonstrated that the antiestrogen fulvestrant markedly affected gene expression in the rat efferent ductules. The mechanism of fulvestrant action to modulate gene expression may involve not only the blockade of ESR1 and ESR2 estrogen receptors, but also the activation of ESR1 and ESR2 when the receptors are tethered to AP-1 or SP1 transcription factors, or the activation of the G protein-coupled estrogen receptor 1. We therefore compared the effects of two strategies to interfere with estrogen action in the rat efferent ductules: treatment with fulvestrant or with the aromatase inhibitor anastrozole. Whereas fulvestrant markedly increased Mmp7 and Spp1, and reduced Nptx1 mRNA levels, no changes were observed with anastrozole. Fulvestrant caused changes in epithelial morphology that were not seen with anastrozole. Fulvestrant shifted MMP7 immunolocalization in the epithelial cells from the supranuclear to the apical region; this effect was less pronounced with anastrozole. In vitro studies of (35)S-methionine incorporation showed that protein release was increased, whereas tissue protein content in the efferent ductules of fulvestrant-treated rats was decreased. Although fulvestrant markedly affected gene expression, no changes were observed on AP-1 and SP1 DNA-binding activity. The blockade of ESRs seems to be the major reason explaining the differences between both treatments. At least some of the effects of fulvestrant appear to result from compensatory mechanisms activated by the dramatic changes caused by ESR1 blockade.

Locally produced relaxin may affect testis and vas deferens function in rats

We have previously shown that the rat testis and vas deferens contain high levels of the relaxin receptor, RXFP1. The present study was undertaken to determine the expression of relaxin in these tissues, and the effect of exogenous relaxin on Sertoli cell proliferation and on the mRNA levels of some proteins that may contribute to epithelial secretion and tissue reorganization in the vas deferens. Relaxin mRNA levels in testis and vas deferens were much lower than in the prostate. Sertoli cells seem to be an important source of relaxin mRNA in testis. Relaxin immunoreactivity was detected in the seminiferous epithelium but not in the interstitial compartment. The relaxin precursor was expressed in the vas deferens, and relaxin immunoreactivity was detected in apical cells of the vas deferens. Castration, but not treatment with the anti-estrogen ICI 182,780, dramatically reduced relaxin mRNA levels in the prostate and vas deferens, and this effect was prevented by testosterone.Rxfp1mRNA levels in the vas deferens and prostate were not affected by castration or treatment with ICI 182,780. Exogenous relaxin increased the incorporation of3H-thymidine in cultured Sertoli cells, and treatment of the vas deferens with 100 ng/ml relaxin increased the mRNA levels for the cystic fibrosis chloride channel (cystic fibrosis transmembrane regulator) about three times, and doubled mRNA levels for the inducible form of nitric oxide synthase and metalloproteinase 7. These results suggest that locally produced relaxin acts as an autocrine or paracrine agent in the testis and vas deferens to affect spermatogenesis and seminal fluid composition.

Peculiar subcellular localization of Fas antigen in human and mouse spermatozoa

The highly polarized structure and function of mammalian spermatozoa dictate that these cells compartmentalize specific metabolic and signaling pathways to regions where they are needed. Fas was initially identified as membrane receptor for pro-apoptotic signals, has been recently recognized as a molecule with pleiotropic functions. In this article, we provide evidence of a peculiar Fas localization: it is closely associated to the perinucleus, mainly at the level of the inner acrosomal membrane, as well as in the inner compartment of mitochondria. Immunoelectron microscopy and Western blot analysis indicated that intracellular Fas was associated with mitochondria in mouse epididymal spermatozoa. Accordingly, also in human ejaculated sperm, immunofluorescence analysis showed Fas localized in the middle piece of sperm flagellum where mitochondria are grouped. The potential functional implications of these findings are discussed.

Effects of the antiestrogen fulvestrant (ICI 182,780) on gene expression of the rat efferent ductules

The efferent ductules express the highest amount of estrogen receptors ESR1 (ERalpha) and ESR2 (ERbeta) within the male reproductive tract. Treatment of rats with the antiestrogen fulvestrant (ICI 182,780) causes inhibition of fluid reabsorption in the efferent ductules, leading to seminiferous tubule atrophy and infertility. To provide a more comprehensive knowledge about the molecular targets for estrogen in the rat efferent ductules, we investigated the effects of ICI 182,780 treatment on gene expression using a microarray approach. Treatment with ICI 182,780 increased or reduced at least 2-fold the expression of 263 and 98 genes, respectively. Not surprisingly, several genes that encode ion channels and macromolecule transporters were affected. Interestingly, treatment with ICI 182,780 markedly altered the expression of genes related to extracellular matrix organization. Matrix metalloproteinase 7 (Mmp7), osteopontin (Spp1), and neuronal pentraxin 1 (Nptx1) were among the most altered genes in this category. Upregulation of Mmp7 and Spp1 and downregulation of Nptx1 were validated by Northern blot. Increase in Mmp7 expression was further confirmed by immunohistochemistry and probably accounted for the decrease in collagen content observed in the efferent ductules of ICI 182,780-treated animals. Downregulation of Nptx1 probably contributed to the extracellular matrix changes and decreased amyloid deposition in the efferent ductules of ICI 182,780-treated animals. Identification of new molecular targets for estrogen action may help elucidate the regulatory role of this hormone in the male reproductive tract.

Expression of Fas and Fas ligand in human testicular germ cell tumours

In the present study, we analysed the expression of Fas ligand (FasL) and its cognate receptor Fas in 14 seminomatous testicular germ cell tumours (TGCT) and six normal testicular tissues obtained following orchiectomy. Tissue samples have been processed to prepare either total RNA or protein extracts or fixed and embedded in paraffin for immunohistochemistry (IHC) experiments. Quantitative RT-PCR experiments demonstrated in TGCT a significant (p < 0.01) increase of the FasL mRNA expression of 21.1 +/- 5.4 fold, with respect to normal tissues. On the contrary, in the same cancer tissues, the levels of Fas mRNA were significantly (p < 0.01) reduced to 0.27 +/- 0.06 fold. These observations were confirmed in western blot experiments showing a significant increase of FasL and a concomitant decrease of Fas proteins in testicular cancer tissues, with respect to normal testis. Moreover, IHC experiments showed a strong FasL immuno-reactivity in six out of eight TGCT samples analysed, while Fas immuno-positivity was found in cancer cells of only two TGCT tissues. In addition, in all tumour samples, infiltrating lymphocytes were Fas positive. However, no correlation could be observed between Fas or FasL mRNA variations and clinical parameters such as patient's age, TNM stage or tumour size. We also compared the serum levels of soluble FasL (sFasL) of 15 patients affected by seminomatous TGCT, of four patients with non-seminomatous TGCT and six age-matched healthy males. No significant differences in sFasL serum level could be identified. In conclusion, our data demonstrated that the majority of seminomas are characterized by an increased expression of FasL and a concomitant reduction of Fas, with respect to human normal testis, and that sFasL serum level is not a tumour marker for patients affected by TGCT.

Relaxin family peptide receptors Rxfp1 and Rxfp2: mapping of the mRNA and protein distribution in the reproductive tract of the male rat

BACKGROUND

Relaxin is the endogenous ligand of the G-protein coupled receptor RXFP1, previously known as LGR7. In humans relaxin can also activate, but with lower affinity, the closely related receptor for the insulin-like peptide from Leydig cells, RXFP2, previously known as LGR8. The lack of relaxin impairs male fertility but the precise distribution and the function of relaxin receptors in the male reproductive tract is not known. We investigated the distribution of Rxfp1 and Rxfp2 in the reproductive tract of the male rat and the function of relaxin in the vas deferens, a tissue with high expression of both receptors.

METHODS

The presence of mRNA for Rxfp1 and Rxfp2 was investigated in testes, cultured Sertoli cells, epididymis, vas deferens, seminal vesicle, prostate, and spermatozoa by RT-PCR and Southern blot. Protein expression in the testis, vas deferens, primary culture of Sertoli cells, and spermatozoa was assessed by immunohistochemistry and immunofluorescence. The role of relaxin in the vas deferens was evaluated by contractility studies and radioimmunoassay of cAMP production. The effect of relaxin on mRNA levels for metalloproteinase-7 was measured by Northern blot.

RESULTS

Transcripts for Rxfp1 and Rxfp2 were present in almost all parts of the male reproductive tract, with high levels in testis and vas deferens. Both receptors were immunolocalized in late stage germ cells but not in mature spermatozoa, although mRNAs for both receptors were also present in mature spermatozoa. Rxfp1 but not Rxfp2 was detected in cultured Sertoli cells. Strong immunostaining for Rxfp1 and Rxfp2 was seen in muscular and epithelial layers of the vas deferens and in arteriolar walls. Relaxin did not affect contractility and cyclic AMP production of the vas deferens, but increased the levels of mRNA for metalloproteinase-7.

CONCLUSION

Rxfp1 and Rxfp2 are widely and similarly distributed throughout the male reproductive tract. Our results suggest that Rxfp1 on spermatids and Sertoli cells may be important in spermatogenesis. Relaxin in the vas deferens does not affect contractility, but may affect vascular compliance and collagen and matrix remodeling.