Lipocalin type prostaglandin D-synthase: which role in male fertility?

Integrative Assessment of Seminal Plasma Biomarkers: A Narrative Review Bridging the Gap between Infertility Research and Clinical Practice

Infertility represents a significant global health challenge impacting millions of couples worldwide. Approximately half of all infertile couples exhibit compromised semen quality, indicative of diminished male fertility. While the diagnosis of male infertility traditionally relies on semen analysis, its limitations in providing a comprehensive assessment of male reproductive health have spurred efforts to identify novel biomarkers. Seminal plasma, a complex fluid containing proteins, lipids, and metabolites, has emerged as a rich source of such indicators. Reproduction depends heavily on seminal plasma, the primary transporter of chemicals from male reproductive glands. It provides a non-invasive sample for urogenital diagnostics and has demonstrated potential in the identification of biomarkers linked to illnesses of the male reproductive system. The abundance of seminal proteins has enabled a deeper understanding of their biological functions, origins, and differential expression in various conditions associated with male infertility, including azoospermia, asthenozoospermia, oligozoospermia, teratozoospermia, among others. The true prevalence of male infertility is understated due to the limitations of the current diagnostic techniques. This review critically evaluates the current landscape of seminal plasma biomarkers and their utility in assessing male infertility. Βy bridging the gap between research and clinical practice, the integrative assessment of seminal plasma biomarkers offers a multimodal approach to comprehensively evaluate male infertility.

Arachidonic Acid Pathways and Male Fertility: A Systematic Review

Arachidonic acid (AA) is a polyunsaturated fatty acid that is involved in male fertility. Human seminal fluid contains different prostaglandins: PGE (PGE₁ and PGE₂), PGF_2α, and their specific 19-hydroxy derivatives, 18,19-dehydro derivatives of PGE₁ and PGE₂. The objective of this study is to synthesize the available literature of in vivo animal studies and human clinical trials on the association between the AA pathway and male fertility. PGE is significantly decreased in the semen of infertile men, suggesting the potential for exploitation of PGE agonists to improve male fertility. Indeed, ibuprofen can affect male fertility by promoting alterations in sperm function and standard semen parameters. The results showed that targeting the AA pathways could be an attractive strategy for the treatment of male fertility.

Influence of Risk Factors for Male Infertility on Sperm Protein Composition

Male infertility is a common health problem that can be influenced by a host of lifestyle risk factors such as environment, nutrition, smoking, stress, and endocrine disruptors. These effects have been largely demonstrated on sperm parameters (e.g., motility, numeration, vitality, DNA integrity). In addition, several studies showed the deregulation of sperm proteins in relation to some of these factors. This review inventories the literature related to the identification of sperm proteins showing abundance variations in response to the four risk factors for male infertility that are the most investigated in this context: obesity, diabetes, tobacco smoking, and exposure to bisphenol-A (BPA). First, we provide an overview of the techniques used to identify deregulated proteins. Then, we summarise the main results obtained in the different studies and provide a compiled list of deregulated proteins in relation to each risk factor. Gene ontology analysis of these deregulated proteins shows that oxidative stress and immune and inflammatory responses are common mechanisms involved in sperm alterations encountered in relation to the risk factors.

Protein markers of spermatogenesis and their potential use in the management of azoospermia

INTRODUCTION

Azoospermia, absence of sperm in the ejaculate is classified as obstructive (OA) and non-obstructive azoospermia (NOA). In OA, sperm are produced, but due to physical obstruction in the male reproductive tract, they are not released in the ejaculate. NOA, on the other hand, is defined as the absence of sperm in the ejaculate due to testicular dysfunction. In NOA, spermatogenesis is frequently preserved in specific sites, and proteomics studies have been employed in order to identify men with preserved spermatogenesis.

AREAS COVERED

Differential protein expression in patients with male infertility is an indicator of impaired spermatogenesis. Here, we reviewed proteins with a potential role as biomarkers of spermatogenesis that could help in the management of non-obstructive and obstructive azoospermia. The following keywords were used for bibliographic research: seminal plasma, proteomics, male infertility, nonobstructive, obstructive, azoospermia, oligospermia.

EXPERT OPINION

Biopsy is an invasive and potentially harmful technique for detecting spermatogenesis in men with OA and NOA. Seminal plasma proteins are highly promising as biomarkers for spermatogenesis. Current literature presents a number of potential candidate biomarkers for determining preserved spermatogenesis.

"Emerging role of Novel Seminal Plasma Bio-markers in Male Infertility: A Review"

Male infertility has emerged as an important cause of infertility worldwide. There are many factors affecting male fertility and research is going on to know impact of various factors on sperm functions. Semen analysis is gold standard diagnostic test for male infertility, but it is crude method for estimation of male infertility as seminal composition gets affected by environmental factors, infections, other pathologies, hence, results of semen analysis either becomes normal/ambiguous, leading to failure of diagnosis and delayed treatment. Hence, with need of newer, better tests for assessing male factor infertility, seminal plasma is being tested for biomarkers. Seminal plasma is considered gold mine for male fertility as it contains molecules from male reproductive glands which play important role in sperm function. Study of seminal plasma molecules can give an idea about sperm concentration, motility, morphology and cause of infertility and can serve as biomarkers for male infertility. Present review briefs on some of these novel seminal plasma biomarkers which may play significant role in male fertility and can be used in future for better identification, assessment of infertile males.

METHODOLOGY

Literature from 1985 to 2019 was searched from various databases including PUBMED, SCOPUS, Google Scholar on seminal plasma biomarkers using keywords: "seminal plasma protein biomarkers", "novel seminal plasma markers and male infertility", "hormones in seminal plasma and male infertility", "oxidative stress and male infertility", "Reactive Oxygen Species and sperm DNA", "immunoinfertility".

INCLUSION CRITERIA

All full length original or review articles or abstracts on seminal plasma markers and male infertility published in English language in various peer-reviewed journals were considered.

EXCLUSION CRITERIA

Articles published in languages other than English were excluded from the study.

RESULTS

Seminal plasma is a big reservoir of molecules derived from the various male reproductive glands which can be used as potential biomarkers of male fertility.

CONCLUSION

Hence, seminal plasma biomarkers can be used in future for better assessment of male factor infertility, its causes and may play an important role in management of male factor infertility.

Gene and protein expression in the reproductive tract of Brazilian Somalis rams

Brazilian Somalis is a locally-adapted breed of rams raised in tropical climate and native pastures. The present study was conducted to evaluate gene expression and proteome of the reproductive tract of such rams. Samples were collected from testes, epididymides, seminal vesicles and bulbourethral glands of four rams. Expression of clusterin (CLU), osteopontin (OPN) and prostaglandin D2 synthase (PGDS) genes were evaluated in all samples by real-time PCR. Shotgun proteomic analysis was performed using samples from the head, corpus and cauda epididymides and from all other structures as well. Gene ontology terms and protein interactions were obtained from UniProtKB databases and MetaCore v.6.8 platform. CLU trasncripts were detected in the testes, epididymides, seminal vesicles and bulbourethral glands of the Somalis rams. The initial region and body of the epididymis had the greatest CLU expression. OPN mRNA was localized in all tissues of the ram reproductive tract. PGDS mRNA was detected in the testes and epididymides. Lable-free mass spectrometry allowed the identification of 137 proteins in all samples. Proteins of the epididymis head mainly participate in cellular processes and response to stimulus, participating in catalityc activity and binding. Proteins of epididymis body acted as regulatory proteins and in cellular processes, with binding and catalytic activity. Cauda epididymis molecules were associated with cellular processes and regulation, with binding function and catalytic activity as well. Testis proteins were mainly linked to cell processes and response to stimuli, and had catalytic function. Seminal vesicle proteins were involved in regulation and mainly with binding functions. Most bulbourethral gland proteins participated in cellular processes. The present study is the first to evaluate the proteome and gene expressions in the reproductive tract of Brazilian Somalis rams. Such pieces of information bring significant cointribution for the understanding of the reproductive physiology of locally-adapted livestock.

Multiple roles of the prostaglandin D2 signaling pathway in reproduction

Prostaglandins signaling molecules are involved in numerous physiological processes. They are produced by several enzyme-limited reactions upon fatty acids, which are catalyzed by two cyclooxygenases and prostaglandin synthases. In particular, the prostaglandins E2(PGE2), D2(PGD2), and F2(PGF2α) have been shown to be involved in female reproductive mechanisms. Furthermore, widespread expression of lipocalin- and hematopoietic-PGD2synthases in the male reproductive tract supports the purported roles of PGD2in the development of both embryonic and adult testes, sperm maturation, and spermatogenesis. In this review, we summarize the putative roles of PGD2signaling and the roles of both PGD2synthases in testicular formation and function. We review the data reporting the involvement of PGD2signaling in the differentiation of Sertoli and germ cells of the embryonic testis. Furthermore, we discuss the roles of lipocalin-PGD2synthase in steroidogenesis and spermatogenesis, in terms of lipid molecule transport and PGD2production. Finally, we discuss the hypothesis that PGD2signaling may be affected in certain reproductive diseases, such as infertility, cryptorchidism, and testicular cancer.

Investigation of galectin-3 function in the reproductive tract by identification of binding ligands in human seminal plasma

PROBLEM

Galectin-3 is a β-galactoside binding protein with immunomodulatory properties and exerts its extracellular functions via interactions with glycoconjugate ligands. Therefore, to elucidate the function of galectin-3, binding ligands in human seminal plasma were investigated.

METHOD OF STUDY

Galectin-3 binding proteins were isolated from seminal plasma by affinity chromatography, and candidate ligands were identified by MS/MS. Biochemical methods were used to characterize the ability of galectin-3 to bind its ligands.

RESULTS

Identified galectin-3 ligands included CD13, MUC6, PAP, PSA, and ZAG. 1D and 2D electrophoretic analysis of seminal plasma demonstrated that CD13, PAP, PSA, and ZAG immunoreactivity co-migrated with galectin-3-reactive protein bands and spots at expected molecular weights and pIs. Inhibition assays indicated that CD13, PSA, PAP, and ZAG interact with galectin-3 in a protein-carbohydrate manner.

CONCLUSION

The galectin-3 binding ligands identified in this study indicate multiple roles for galectin-3 in the reproductive and immunological functions of seminal plasma.

Characteristic of PGDS potential regulation role on spermatogenesis in the Chinese mitten crab Eriocheir sinensis

Prostaglandin D synthase (PGDS) catalyzes the isomerization of PGH2 to produce PGD2 in the presence of sulfhydryl compounds. In this study, a full length PGDS gene comprising 1250 nucleotides from the Chinese mitten crab Eriocheir sinensis (Es-PGDS) was characterized, with a 615 bp open reading frame encoding 204 amino acid residues. Its deduced peptide has high homology with other species' PGDS protein. The Es-PGDS mRNA expression was tissue-related, with the highest expression observed in the hepatopancreas, accessory sex gland, testis and ovaries. We also detected the different stages of tissue expression and the enzyme activity for Es-PGDS in the testis and male crab hepatopancreas. The different expression patterns and its corresponding enzyme activity level indicated that PGDS is involving in the regulation of reproductive action during the period of rapid development in E. sinensis. Furthermore our research could arouse a heat debate on the PGDS reproductive function in invertebrate and further study will be needed to determine the molecular mechanism(s) linking PGDS functions to spermatogenesis and ontogenesis if this gene is to be exploited as a molecular biomarker in further studies of development.

Characteristics of selected seminal plasma proteins and their application in the improvement of the reproductive processes in mammals

Understanding the biochemical processes associated with ovum fertilization and knowledge about the structure and function of individual substances participating in these processes is crucial for the development of biotechnological methods to improve reproduction of animals and humans. Among many components of seminal plasma, proteins and peptides play a specific role in regulation of the fertilization process, particularly through their ability to bind various types of ligands such as polysaccharides, lipids and ions. Heparin-binding proteins regulate capacitation and acrosome reaction processes. Affinity of plasma proteins to mannans of the fallopian tube epithelium facilitates formation of spermatozoa reservoirs in the female reproductive tract. Ability to bind phosphorylcholine is one of the conditions for the coating of the seminal plasma proteins on the sperm membrane and also determines the formation of oligomeric forms of certain proteins. Zinc binding by seminal plasma proteins regulates sperm chromatin condensation state. It also affects motility of these cells and acrosome reaction. The interspecies analysis indicates significant structural and functional similarities, especially for the proteins with low molecular weight. Fertility associated proteins (FAPs) have been determined in the bull, stallion, boar, ram and dog. The contents of these proteins correlate with the indicators of the fertilizing abilities of sperm. In humans, several seminal plasma proteins were found which serve as diagnostic markers of spermatogenesis, seminiferous epithelium state, and azoospermia. To determine the semen ability for preservation, measurement of some seminal plasma protein content may also be used. Addition of specific plasma proteins to a spermatozoa solution undergoing the process of preservation may be used to retain the features of the cells responsible for efficient fertilization.

Isolation of lipocalin-type protein from rainbow trout seminal plasma and its localisation in the reproductive system

The lipocalin protein family is a large and diverse group of small extracellular proteins characterised by their ability to bind hydrophobic molecules. In the present study, we describe the isolation procedure for rainbow trout seminal plasma protein, characterised by a moderate migration rate during polyacrylamide gel electrophoresis, providing information regarding its basic features and immunohistochemical localisation. This protein was identified as a lipocalin-type protein (LTP). The molecular mass of LTP was found to be 18 848 Da and it was found to lack any carbohydrate components. Only a few Salmoniformes contain LTP in their seminal plasma. The abundance of LTP in the Sertoli and Leydig cells of the testes of the rainbow trout, as well as in secretory cells of the efferent duct, suggests that this protein is specific for rainbow trout milt, where it acts as a lipophilic carrier protein. Moreover, the specific localisation of LTP in the flagella of the spermatozoa suggests a role for LTP in sperm motility. Further experiments are necessary to identify the endogenous ligands for LTP in rainbow trout seminal plasma and to characterise the binding properties of this protein.

Single-chain antibody against human lipocalin-type prostaglandin D synthase: construction, expression, purification, and activity assay

An active form of single-chain antibody (ScFv) from murine monoclonal antibody 4A7, which is specific for lipocalin-type prostaglandin D synthase (L-PGDS), was produced in Escherichia coli. The complementary DNA fragments encoding the variable regions of heavy chain (VH) and light chain (VL), which amplified from hybridoma 4A7 producing a monoclonal antibody (IgG1) against L-PGDS, were connected by a (Gly4Ser)3 linker using an assembly polymerase chain reaction. The resultant ScFv were cloned into the vector pGEM and expressed in E. coli as inclusion bodies. The expressed ScFv fusion proteins were purified by Ni2+-nitrilotriacetic acid chromatography. The purity and activity of purified ScFv were confirmed by SDS-PAGE and ELISA. The result revealed that 4A7 ScFv conserved the same characteristics of specific recognition and binding to sperm as the parental 4A7 monoclonal antibody.

Different expression of lipocalin-type prostaglandin D synthase in rat epididymidis

This study was designed to explore the different expression of L-PGDS (lipocalin-type prostaglandin D synthase) in rat epididymidis and to gain further insight into the potential function of L-PGDS in male reproduction. The expression of L-PGDS in rat epididymidis was assessed using real-time quantitative PCR and immunoblotting. The distribution of L-PGDS in rat epididymidis was explored by immunohistochemical methods. The result of immunohistochemistry displayed that L-PGDS was mainly distributed in epididymidis and localized within the cytoplasm and the cilia of the epithelial cells. Real-time quantitative PCR and immunoblotting showed that L-PGDS was strikingly expressed in the caput epididymidis, while a moderate to weak expression was observed in the corpus and cauda epididymidis, the level of mRNA was 0.52+/-0.02 in the caput, 0.48+/-0.03 in the corpus and 0.32+/-0.01 in the cauda epididymidis, the level of protein expression in caput, corpus and the cauda groups was 1, 0.89+/-0.03 and 0.62+/-0.01, which suggested that L-PGDS may play certain kind of role during the process of the spermatozoa maturation.

Relationship between lipocalin-type prostaglandin D synthase and α-glucosidase in azoospermia seminal plasma

BACKGROUND

[corrected] To determine the correlation of lipocalin-type prostaglandin D synthase (L-PGDS) and alpha-glucosidase in semen.

METHODS

We analyzed 68 seminal plasmas for lipocalin-type prostaglandin D synthase (L-PGDS) and alpha-glucosidase, L-PGDS was analyzed by ELISA. The semen donors were categorized in 3 groups: normal, obstructive and non-obstructive azoospermia. We then evaluated their correlation.

RESULTS

The difference of L-PGDS concentration (P<0.001) and alpha-glucosidase activity (P<0.001) among the 3 clinical groups was statistically significant. Correlation between L-PGDS concentration and alpha-glucosidase was also statistically significant. L-PGDS concentration correlated positively with alpha-glucosidase activity (r=0.882).

CONCLUSIONS

L-PGDS in seminal plasma, like alpha-glucosidase, suggests an obstruction of the seminal ducts and may be a potential marker that may aid in the differential diagnosis of obstructive and non-obstructive azoospermia.

Expression and Regulation of Lipocalin-Type Prostaglandin D Synthase in Rat Testis and Epididymis1

Lipocalin-type prostaglandin D synthase (L-PGDS), a bifunctional protein, is expressed in the male reproductive organs of many species. However, the expression and regulation of L-PGDS in rat are still uncertain. The present study investigated the regionalization and regulation of L-PGDS expression in rat testis and epididymis by in situ hybridization and immunohistochemistry under the conditions of sexual maturation, castration, and ethylene dimethane sulfonate (EDS) treatments. In sexually mature rats, L-PGDS mRNA was weakly expressed only in the testicular peritubular cells, whereas L-PGDS immunostaining was highly detected in the Leydig cells by Day 70 postpartum. During sexual maturation, L-PGDS mRNA expression was highly detected in the caput, corpus, and cauda of the epididymis 70 days after birth. Compared with normal L-PGDS expression in adult epididymis, both L-PGDS mRNA expression and protein immunostaining were significantly reduced in the caput, corpus, and cauda epididymis after castration. Testosterone propionate treatment induced a significant increase of L-PGDS expression in the epididymis of castrated rats. Compared with adult rat epididymis, L-PGDS mRNA and protein expression was down-regulated after EDS treatment. Testosterone propionate treatment could induce an increase of L-PGDS mRNA and protein expression in the epididymis of EDS-treated rats. In conclusion, both castration and EDS treatments caused a significant decrease of L-PGDS expression in the epididymis, whereas testosterone propionate treatment could induce an increase of L-PGDS expression in the epididymis of both castrated and EDS-treated rats, indicating that L-PGDS expression in the rat epididymis can be up-regulated by testosterone.