Expression of a common secretory granule specific protein as a marker for the extracellular organelles (prostasomes) in human semen

A comprehensive study to delineate the role of an extracellular vesicle-associated microRNA-29a in chronic methamphetamine use disorder

Extracellular vesicles (EVs), which express a repertoire of cargo molecules (cf. proteins, microRNA, lipids, etc.), have been garnering a prominent role in the modulation of several cellular processes. Here, using both non-human primate and rodent model systems, we provide evidence that brain-derived EV (BDE) miRNA, miR-29a-3p (mir-29a), is significantly increased during chronic methamphetamine (MA) exposure. Further, miR-29a levels show significant increase both with drug-seeking and reinstatement in a rat MA self-administration model. We also show that EV-associated miR-29a is enriched in EV pool comprising of small EVs and exomeres and further plays a critical role in MA-induced inflammation and synaptodendritic damage. Furthermore, treatment with the anti-inflammatory drug ibudilast (AV411), which is known to reduce MA relapse, decreased the expression of miR-29a and subsequently attenuated inflammation and rescued synaptodendritic injury. Finally, using plasma from MUD subjects, we provide translational evidence that EV-miR29a could potentially serve as a biomarker to detect neuronal damage in humans diagnosed with MA use disorder (MUD). In summary, our work suggests that EV-associated miR-29a-3p plays a crucial role in MUD and might be used as a potential blood-based biomarker for detecting chronic inflammation and synaptic damage.

Effects on prostate cancer cells of targeting RNA polymerase III

RNA polymerase (pol) III occurs in two forms, containing either the POLR3G subunit or the related paralogue POLR3GL. Whereas POLR3GL is ubiquitous, POLR3G is enriched in undifferentiated cells. Depletion of POLR3G selectively triggers proliferative arrest and differentiation of prostate cancer cells, responses not elicited when POLR3GL is depleted. A small molecule pol III inhibitor can cause POLR3G depletion, induce similar differentiation and suppress proliferation and viability of cancer cells. This response involves control of the fate-determining factor NANOG by small RNAs derived from Alu short interspersed nuclear elements. Tumour initiating activity in vivo can be reduced by transient exposure to the pol III inhibitor. Untransformed prostate cells appear less sensitive than cancer cells to pol III depletion or inhibition, raising the possibility of a therapeutic window.

Prostasomes: Their Characterisation: Implications for Human Reproduction: Prostasomes and Human Reproduction

The prostate is a principal accessory genital gland that is vital for normal fertility. Epithelial cells lining the prostate acini release in a defined fashion (exocytosis) organellar nanosized structures named prostasomes. They are involved in the protection of sperm cells against immune response in the female reproductive tract by modulating the complement system and by inhibiting monocyte and neutrophil phagocytosis and lymphocyte proliferation. The immunomodulatory function most probably involves small non-coding RNAs present in prostasomes. Prostasomes have also been proposed to regulate the timing of sperm cell capacitation and induction of the acrosome reaction, since they are rich in various transferable bioactive molecules (e.g. receptors and enzymes) that promote the fertilising ability of sperm cells. Antigenicity of sperm cells has been well documented and implicated in involuntary immunological infertility of human couples, and antisperm antibodies (ASA) occur in several body fluids. The propensity of sperm cells to carry attached prostasomes suggests that they are a new category of sperm antigens. Circulating human ASA recognise prostasomes, and among 12 identified prostasomal antigens, prolactin- inducible protein (95 %) and clusterin (85 %) were immunodominant at the expense of the other 10 that were sporadically occurring.

Exosomes: Implications in HIV-1 Pathogenesis

Exosomes are membranous nanovesicles of endocytic origin that carry host and pathogen derived genomic, proteomic, and lipid cargos. Exosomes are secreted by most cell types into the extracellular milieu and are subsequently internalized by recipient cells. Upon internalization, exosomes condition recipient cells by donating their cargos and/or activating various signal transduction pathways, consequently regulating physiological and pathophysiological processes. The role of exosomes in viral pathogenesis, especially human immunodeficiency virus type 1 [HIV-1] is beginning to unravel. Recent research reports suggest that exosomes from various sources play important but different roles in the pathogenesis of HIV-1. From these reports, it appears that the source of exosomes is the defining factor for the exosomal effect on HIV-1. In this review, we will describe how HIV-1 infection is modulated by exosomes and in turn how exosomes are targeted by HIV-1 factors. Finally, we will discuss potentially emerging therapeutic options based on exosomal cargos that may have promise in preventing HIV-1 transmission.

Mycophenolic acid-induced replication arrest, differentiation markers and cell death of androgen-independent prostate cancer cells DU145

Inosine 5'-monophosphate dehydrogenase inhibitors including mycophenolic acid (MPA) are effective inducers of terminal differentiation in a variety of distinct human tumor cell types. Here, we report that MPA also induces such a differentiation in the androgen-independent prostate cancer derived cell line DU145. MPA evoked replication arrest and accumulation of the DU145 cells in the S-phase of the cell cycle. The inhibitor also induced the expression of CD55, clusterin, granulophysin, glucose-regulated protein 78, vasoactive intestinal polypeptide and prostate-specific transglutaminase, which are differentiation markers associated with the phenotype of normal prostate cells. We suggest that inosine 5'-monophosphate dehydrogenase inhibitors, which are already used for the treatment of other diseases, may be used as potential differentiation therapy drugs to control prostate cancer.

Prostasomes--their effects on human male reproduction and fertility

The prostate is a glandular male accessory sex organ vital for normal fertility. It provides the prostatic component of seminal plasma which nourishes and protects sperm following ejaculation. Prostasomes are small (40-500 nm) membrane-bound vesicles produced by epithelial cells lining the prostate acini and are a component of prostatic secretions. Although the existence of these particles has been known for many years, their full function and relevance to reproductive health are largely unknown. Proteomic studies have shown a wide range of proteins (enzymes, structural proteins and novel, unannotated proteins) present in or on the surface of prostasomes providing them with a diverse nature. Interestingly prostasomes are able to fuse with sperm, this event and the associated transfer of proteins lies at the heart of many of their proposed functions. Sperm motility is increased by the presence of prostasomes and their fusion prevents premature acrosome reactions. Prostasomes have been shown to aid protection of sperm within the female reproductive tract because of immunosuppressive, antioxidant and antibacterial properties. Clinically these functions imply a role for prostasomes in male factor infertility. However, the very functions that promote fertility may have negative connotations in later life; recent work has suggested that prostasomes are involved in prostate cancer. Clearly more work is needed to clarify the role of these novel particles and their impact on men's health.

Differentiation of human prostate cancer PC-3 cells induced by inhibitors of inosine 5'-monophosphate dehydrogenase

To establish a system to study differentiation therapy drugs, we used the androgen-independent human prostate PC-3 tumor cell line as a target and mycophenolic acid (MPA), tiazofurin, or ribavirin, which are inhibitors of IMP dehydrogenase, as inducers. These inhibitors evoked replication arrest, caused an increase in cell size, and triggered vacuolization of the cytoplasm. By Northern and Western blotting and immunostaining, we demonstrated MPA-induced expression of 12 proteins reported to reside in prostasomes, organelles released by secretory luminal prostate cells. Additional MPA-induced proteins were identified by two-dimensional gel electrophoresis. Among these was keratin 17, a prostate cell differentiation marker. By Northern blotting, we also demonstrated the constitutive expression of keratins 8 and 18 and induced expression of keratin 19, three other prostate cell differentiation markers. In addition, we established that cells were committed to differentiate after the 2nd day of MPA treatment using guanosine, which can abrogate the effects of MPA. Based on the expression patterns of prostasomal proteins and keratins and the presence of tentative secretory vacuoles, we hypothesize that IMP dehydrogenase inhibitors induce androgen-independent PC-3 cells to mature into cells with a phenotype that resembles normal prostate luminal cells, but at their intermediate state of differentiation.

Effect of Prostatein, the Major Protein Produced by the Rat Ventral Prostate, on Phagocytic Cell Functions

PROBLEM

To determine whether prostatein, the major protein produced and secreted into the seminal fluid by the rat ventral prostate has any effect on the phagocytic cell functions in vitro.

METHOD OF STUDY

Analysis was done by determining if purified prostatein added to cells obtained from the peritoneal cavity has any effect on their phagocytic and intracellular killing capacity. Also, we analyzed the effect of prostatein on the production of oxygen and nitrogen intermediates, measuring these metabolites by Nitroblue tetrazolium assay and by the Griess reaction respectively.

RESULTS

Prostatein possess the ability to inhibit in vitro the phagocytic and killing properties of peritoneal rat leukocytes in a dose-dependent manner. The addition of a polyclonal antiserum against prostatein specifically blocks this inhibitory effect. Moreover, prostatein inhibits the production of oxygen and nitrogen intermediates by these cells.

CONCLUSION

Regulation of the production of reactive oxygen species in the reproductive tract is extremely necessary to avoid their deleterious effects on the sperm motility and the fertilization process. We propose that prostatein, a protein supplied by an accessory gland like prostate, can inhibit the macrophage function, showing an important antioxidant effect.

Identification of rat prostatic steroid binding protein (PSBP) as an immunosuppressive factor

Prostatic steroid binding protein (PSBP) is the major protein produced ( approximately 20% of the total cytosolic protein) and secreted into the seminal fluid by the rat ventral prostate but its physiological function has not been elucidated yet. Since PSBP is secreted into the seminal fluid (which is itself a potent immunosuppressor) and has strong homology with uteroglobin (which possess an important anti-inflammatory function) our aim was to determine what effect, if any, PSBP would have on the immune system. With that purpose in mind we performed mononuclear cell cultures in the presence or absence of purified PSBP and analysed the effect of this protein on different functional parameters. PSBP inhibits the mitogen-induced proliferation of normal rat spleen mononuclear cells (MNC) specifically and in a dose-dependent manner. It reduces the production of IL-2 and the expression of its receptor (analysed by flow cytometry) which are important events for lymphocyte proliferation. Also, PSBP was able to inhibit OVA-specific proliferation of lymph node cells from previously primed animals. The immunosuppressive effect of PSBP is not due to an inherent toxic effect to the cells, since the cell viability was kept intact at the different times of culture studied. We also analysed the effect of rat PSBP on mitogen-induced proliferation of mouse spleen and human blood MNC. The proliferation was strongly abolished in a dose-dependent and non-species specific fashion. Moreover, PSBP strongly inhibits the human mixed lymphocyte reaction. Taken together, the present data support evidence for a new type of function for PSBP. We report that PSBP is a potent immunosuppressor factor and we describe its effect on the immune function in vitro. Here, we discuss the possible implications of these findings in the protection of sperm from immunologic damage in the feminine reproductive tract.

Fatty acid pattern of human prostasome lipid

Prostasomes are organelles of prostatic origin found in human semen. Their average diameter is about 150 nm and they appear as a lipoprotein membrane surrounding less organized material. Their lipid composition is peculiar, having much cholesterol and sphingomyelin. On the other hand, many of their proteins possess catalytic activity and are involved in the immune response. In previous work, we have shown that prostasomes may fuse to sperm at slightly acidic pH values, thereby modifying the composition of the sperm plasma membrane. In this paper, we examine the fatty acid pattern of prostasome lipid and find that it is completely different from that of sperm membrane lipid. Polyunsaturated phosphatidylcholines, common in sperm membrane, are rare in prostasome. Therefore, the fusion between prostasomes and sperm should stabilize sperm plasma membrane by enriching it in cholesterol, sphingomyelin, and saturated glycerophospholipid. This would prevent the untimely occurrence of the acrosome reaction.

Expression and enzymic activity of ecto 5'-nucleotidase in the human male genital tract

Human 5'-nucleotidase (5'-NT, EC 3.1.3.5) is an enzyme that hydrolyzes nucleotides such as AMP or IMP (inosine 5'-monophosphate) into inorganic phosphate and the respective nucleoside. It has been suggested that the enzyme acts as a scavenger of injured cell or membrane components or as a supplier of adenosine. We have purified to homogeneity human 5'-NT, a 69-kDa glycoprotein containing a glycosylphosphatidylinositol anchor, present in human seminal fluid. With use of a polyclonal rabbit antiserum against the protein, a strong immunoreaction was detected in prostatic epithelium, exceeding that in placental syncytiotrophoblast and amnion cells. A slightly less intense immunoreaction was present in some cells of seminal vesicle epithelium and in vesicular intraluminal secretion. In the epididymis, only the apical cell portion and particularly the stereocilia of the epididymal principal cells, as well as clusters of small nonciliated cells in the efferent ductules, were immunoreactive. In the testis, no immunoreactive cells at all were detected, and likewise no clear-cut signal was observed in testicular and epididymal spermatozoa. The immunohistochemical results were coincident with Western blots prepared from homogenates of the respective tissues. Reverse transcription-polymerase chain reaction studies were performed with primers derived from the sequence of human placental ecto 5'-NT. Using human placenta as a reference tissue, positive results were obtained in the epididymis, seminal vesicle, and prostate, but not in the testis. On Northern blots, we determined the size of the mRNA at 2.4 kilobases. The relatively strong expression of 5'-NT in the human male accessory sex glands points to a potential regulatory role of the enzyme during posttesticular modification of the sperm surface.

Monoclonal antibodies against human prostasomes

BACKGROUND

The prostasomes are secreted into the gland ducts of the human prostate. At ejaculation, these native prostasomes are expelled with the secretions of the prostate and appear in the seminal plasma as seminal prostasomes, where they facilitate sperm function in various ways. We have designed methods for producing monoclonal anti-prostasome antibodies to be used for immunohistochemistry and sequencing analyses of the prostasomes.

METHODS

The immunogen applied was purified seminal prostasomes placed on small pieces of nitrocellulose membranes (prostasome blots) and deposited into the spleen of mice for immunization. For screening, both seminal and native prostasomes were used.

RESULTS

We obtained antibodies which detected native prostasomes both in prostatic secretions and in paraffin sections of the prostate. The immunostaining demonstrated that all prostate epithelial cells contained prostasomes. They were located in the apical parts of the secretory cells and in the gland ducts, while the nuclei and the corpora amylacea were unstained.

CONCLUSIONS

Using the methods described, monoclonal antibodies against native prostasomes were produced. In addition to their usefulness in structural and functional studies of prostasomes, specific monoclonal antibodies can be used to characterize prostasomes by sequencing analyses.

The role of apocrine released proteins in the post-testicular regulation of human sperm function

A unifying hypothesis is presented postulating an apocrine release of several seminal proteins which mix and reaggregate in seminal fluid, thereby eventually forming particles designated either as "prostasomes", "vesiculosomes" or "seminosomes". The term "aposomes" should be restricted to the blebs released from secretory cells in the rat dorsal prostate and coagulating gland. Three different proteins present in human seminosomes along with the respective antibodies have been used to identify the localization, function and hypothetical interaction with spermatozoa. The proteins were (1) seminal vesicle-derived fibronectin, (2) prostate-derived 5'-nucleotidase and (3) a hitherto unidentified 100 kD membrane protein from epididymis, seminal vesicle and prostate. I. Fibronectin is an extracellular matrix protein which is also secreted from the seminal vesicles participating in the formation of the seminal clot. Immunofluorescence and immunoelectron microscopy revealed a relatively broad distribution pattern of fibronectin immunoreactivity on spermatozoa from different donors. Adding a fibronectin antiserum at a moderate dilution to vital spermatozoa in vitro resulted in a significant increase in sperm motility. Purified plasma fibronectin added at various concentrations to a vital sperm preparation was found to inhibit sperm motility in a dose-dependent manner. Measurement of calcium fluxes in individual sperm in the presence of fibronectin showed a significant increase. These findings point to a possible post-testicular regulatory function of seminal fibronectin. 2.5'-Nucleotidase (5'-NT) is an enzyme that hydrolyzes nucleotides such as AMP or IMP into inorganic phosphate and the respective nucleoside. The highest amount and activity of 5'-nucleotidase was present in glandular cells of the prostate; much less was detected in seminal vesicles and epididymis. On spermatozoa, the enzyme was localized on the outer leaflet of the plasma membrane covering the acrosomal region. Addition of purified enzyme to an in vitro incubation system of spermatozoa had no effect on sperm motility. A slight reduction of overall motility, however, was observed after addition of 5'-NT antibody to the spermatozoa. When 5'-nucleotidase inhibitors and adenosine channel antagonists were added to the sperm incubation system, a clear-cut inhibition of sperm motility occurred in a dose-dependent manner. This result is interpreted as indicating a significant role of ecto-5'-nucleotidase in the regulation of sperm motility. 3. A polyvalent antiserum against native human prostasomes recognized antigens in the range of 10-14 kD and of approximately 100 kD, respectively, in seminal fluid and prostate homogenates. Immunohistochemical studies revealed the presence of respective antigens in the epididymis, seminal vesicles and the prostate. Immunoelectron microscopy of ultracryo-sections showed labeling both of the apical plasma membrane in the prostate, as well as intraluminal secretory particles indicating the apocrine i.e. plasma-membrane bounded release of these particles. The secretory elements are termed "seminosomes". An affinity-purified fraction within the antiserum recognizes a 100 kD protein which is present both in the apical plasma membrane of the male genital glands, but also in the sperm head and principal piece of human spermatozoa. Incubation of spermatozoa with seminosomes and the respective purified antiserum had no effect on sperm motility. This is in contradistinction to former reports on motility increase induced by the so-called prostasomes.

Immunohistochemistry of prostasomes from human semen

BACKGROUND

To elucidate the origin of so-called "prostasomes" in human semen, a polyvalent rabbit antiserum was produced against a highly purified preparation of these secretory particles.

METHODS

An immunoaffinity selected fraction of the antiserum contained one antibody which in Western blots of prostate extracts showed a 100 kDa band.

RESULTS

Semithin sections processed for immunohistochemistry by using this immunoselected antibody presented a distinct immunoreaction at the apical plasma membrane of secretory cells. The immunoreaction was not organ specific, but was present also in seminal vesicles, epididymis, salivary glands, and kidney. As spermatozoa present in epididymis and seminal vesicles were likewise immunoreactive, a polytopic origin of the respective antigen was concluded.

CONCLUSIONS

Prostatsomes therefore should rather be designated as "seminosomes" which more clearly refers to the composite origin of these particles.

Prostasomes are neuroendocrine-like vesicles in human semen

BACKGROUND

Prostasomes are prostate-derived organelles that exist extracellularly in human seminal plasma.

METHODS

In this study, we have investigated and characterized human prostasomes with regard to their contents of synaptophysin, members of the chromogranin family, and some neuropeptides.

RESULTS

By radioimmunoassay measurement and electron microscopy we show the presence of the neuroendocrine markers chromogranin B, neuropeptide Y, and vasoactive intestinal polypeptide in about equimolar amount in human prostasomes and chromogranin A in about 2% of that amount. To our knowledge, such a high ratio of chromogranin B to chromogranin A has never before been observed. The membrane-bound protein synaptophysin, a well-established immunocytochemical marker for neuroendocrine cells and neurones, was also detected. Hence, we show that synaptophysin could be used as a marker for intact prostasomes.

CONCLUSIONS

The presence of synaptophysin has recently been shown in the serotonincontaining vesicles in platelets. A protein with a similar structure denoted granulophysin has been found in granulocytes and prostasomes. It is suggested that synaptophysin and granulophysin molecules are members of a family of proteins, maybe expressed in all cells that have regulated release of granule content. Our presented data indicate a neurotransmittor function of the prostasomes. The target cells are however not known but could be either the spermatozoa, the epithelial mucous cells of the uterus or tubas or perhaps the ovum.

Soluble CD46 (membrane cofactor protein, MCP) in human reproductive tract fluids

CD46 (membrane cofactor protein, MCP) is a cell surface complement regulatory protein which may have an additional role in human sperm-egg interaction. A soluble form (sCD46) has also been detected in a number of biological fluids, most notably seminal plasma. The present study has employed a monoclonal antibody-based ELISA to assay sCD46 in reproductive tract fluids in normal and pathological conditions. Large amounts of sCD46 were detected in seminal plasma of both fertile and infertile men (combined mean, 4859 ng/ml). Vasectomized men had lower levels (mean, 2421 ng/ml), indicating contributory sources both before and after the vas deferens ligation site. Pre-colostrum also contained relatively high quantities (mean, 445 ng/ml), whereas breast milk (mean, 117 ng/ml), peritoneal fluid (mean, 154 ng/ml) and follicular fluid (mean, 107 ng/ml), as well as uterine (mean, 208 ng/ml), umbilical (mean, 166 ng/ml) and peripheral (mean, 206 ng/ml) blood plasma, had sCD46 levels within a comparable range. Amniotic fluid had low sCD46 concentrations (mean, 22 ng/ml). In endometriosis, peritoneal fluid levels of sCD46 were significantly raised (mean, 199 mg/ml). These results indicate distinctive fluid compartmentalisation of sCD46 consistent with a biological function in human reproductive tract fluids.

Immunomodulatory effects of extracellular secretory vesicles isolated from bovine semen

We demonstrate that extracellular secretory vesicles isolated from bovine seminal plasma have immunomodulatory properties. They inhibit mitogen induced proliferation of bovine and human peripheral blood lymphocytes in a dose dependent fashion. They also inhibit phagocytosis of latex particles by bovine neutrophils. Phagocytosis of opsonised Staphylococcus aureus however was not affected. Furthermore phorbol ester and chemotactic peptide induced superoxide production was decreased especially when a suboptimal dose of stimulants was used. We suggest that extracellular secretory vesicles may preserve sperm survival in the female reproductive tract.