Activity of testis angiotensin converting enzyme (ACE) in ejaculated human spermatozoa

Insights into crucial molecules and protein channels involved in pig sperm cryopreservation

Cryopreservation is the most efficient procedure for long-term preservation of mammalian sperm; however, its use is not currently dominant for boar sperm before its use for artificial insemination. In fact, freezing and thawing have an extensive detrimental effect on sperm function and lead to impaired fertility. The present work summarises the basis of the structural and functional impact of cryopreservation on pig sperm that have been extensively studied in recent decades, as well as the molecular alterations in sperm that are related to this damage. The wide variety of mechanisms underlying the consequences of alterations in expression levels and structural modifications of sperm proteins with diverse functions is detailed. Moreover, the use of cryotolerance biomarkers as predictors of the potential resilience of a sperm sample to the cryopreservation process is also discussed. Regarding the proteins that have been identified to be relevant during the cryopreservation process, they are classified according to the functions they carry out in sperm, including antioxidant function, plasma membrane protection, sperm motility regulation, chromatin structure, metabolism and mitochondrial function, heat-shock response, premature capacitation and sperm-oocyte binding and fusion. Special reference is made to the relevance of sperm membrane channels, as their function is crucial for boar sperm to withstand osmotic shock during cryopreservation. Finally, potential aims for future research on cryodamage and cryotolerance are proposed, which might be crucial to minimise the side-effects of cryopreservation and to make it a more advantageous strategy for boar sperm preservation.

Testicular ACE regulates sperm metabolism and fertilization through the transcription factor PPARγ

Testis angiotensin-converting enzyme (tACE) plays a critical role in male fertility, but the mechanism is unknown. By using ACE C-domain KO (CKO) mice which lack tACE activity, we found that ATP in CKO sperm was 9.4-fold lower than WT sperm. Similarly, an ACE inhibitor (ACEi) reduced ATP production in mouse sperm by 72%. Metabolic profiling showed that tACE inactivation severely affects oxidative metabolism with decreases in several Krebs cycle intermediates including citric acid, cis-aconitic acid, NAD, α-ketoglutaric acid, succinate, and L-malic acid. We found that sperms lacking tACE activity displayed lower levels of oxidative enzymes (CISY, ODO1, MDHM, QCR2, SDHA, FUMH, CPT2, and ATPA) leading to a decreased mitochondrial respiration rate. The reduced energy production in CKO sperms leads to defects in their physiological functions including motility, acrosine activity, and fertilization in vitro and in vivo. Male mice treated with ACEi show severe impairment in reproductive capacity when mated with female mice. In contrast, an angiotensin II receptor blocker (ARB) had no effect. CKO sperms express significantly less peroxisome proliferators-activated receptor gamma (PPARγ) transcription factor, and its blockade eliminates the functional differences between CKO and WT sperms, indicating PPARγ might mediate the effects of tACE on sperm metabolism. Finally, in a cohort of human volunteers, in vitro treatment with the ramipril or a PPARγ inhibitor reduced ATP production in human sperm and hence its motility and acrosine activity. These findings may have clinical significance since millions of people take ACEi daily, including men who are reproductively active.

Quantitative proteomics profiling of spermatozoa and seminal plasma reveals proteins associated with semen quality in Bos indicus bulls

Cattle breeding approaches are an evolving field of research in veterinary science. Certain factors such as Ejaculate Rejection Rate (ERR) pose a limitation to such approaches. In this regard, we sought to investigate the spermatozoa and seminal plasma proteome of Hallikar bulls with low (n = 3) and high (n = 3) ERR. Through the Tandem mass spectrometry approach, we identified a total of 2409 proteins, in which 828 proteins were common in both the semen components, whereas 375 and 378 proteins were unique to spermatozoa and seminal plasma respectively. Tandem mass tags (TMT) based protein quantification resulted in 75 spermatozoal, and 42 seminal plasma proteins being differentially regulated between high and low ERR bulls. Proteins such as SPADH2, TIMP-2, and PLA2G7 which are negative regulators of motility were upregulated in the seminal plasma of high ERR bulls. Proteins such as OAZ3, GPx4, and GSTM3 whose upregulation leads to reduced motility were upregulated in the spermatozoa of high ERR bulls. Caltrin and ADM proteins that enhance sperm motility were downregulated in the seminal plasma of high ERR bulls. The regulation of ACE, a negative regulator of sperm motility was upregulated in both the spermatozoa and seminal plasma of high ERR bulls. SIGNIFICANCE: The saying "Bull is more than half of the herd" signifies the importance of bull in the genetic improvement of the herd. Traditionally used semen quality tests will provide limited information about the potential fertility of bulls. The proteomics approach is a promising omics technology to understand the factors involved in male fertility. The present study identified the spermatozoal and seminal plasma proteins that are differentially regulated between high and low ERR bulls. Sperm motility-associated proteins are differentially regulated. This study if improved further, can be used to develop markers associated with semen quality which is useful for the selection of bulls.

Implications of testicular ACE2 and the renin-angiotensin system for SARS-CoV-2 on testis function

Although many studies have focused on SARS-CoV-2 infection in the lungs, comparatively little is known about the potential effects of the virus on male fertility. SARS-CoV-2 infection of target cells requires the presence of furin, angiotensin-converting enzyme 2 (ACE2) receptors, and transmembrane protease serine 2 (TMPRSS2). Thus, cells in the body that express these proteins might be highly susceptible to viral entry and downstream effects. Currently, reports regarding the expression of the viral entry proteins in the testes are conflicting; however, other members of the SARS-CoV family of viruses - such as SARS-CoV - have been suspected to cause testicular dysfunction and/or orchitis. SARS-CoV-2, which displays many similarities to SARS-CoV, could potentially cause similar adverse effects. Commonalities between SARS family members, taken in combination with sparse reports of testicular discomfort and altered hormone levels in patients with SARS-CoV-2, might indicate possible testicular dysfunction. Thus, SARS-CoV-2 infection has the potential for effects on testis somatic and germline cells and experimental approaches might be required to help identify potential short-term and long-term effects of SARS-CoV-2 on male fertility.

Localization and Distribution of Testicular Angiotensin I Converting Enzyme (ACE) in Neck and Mid-Piece of Spermatozoa from Infertile Men in Relation to Sperm Motility

Testicular angiotensin converting enzyme (ACE) is known to play an essential role in the male reproduction and fertility. Data about tACE in cases of male infertility are quite scarce, and in this respect we aimed to study localization and distribution of tACE protein in the neck and mid-piece of spermatozoa from pathological samples in relation to sperm motility. The enzyme expression during capacitation and acrosome reaction was quantitatively assessed. In human ejaculated spermatozoa tACE is localized on sperm plasma membrane of the head, the neck and mid-piece of the tail. The immunoreactivity becomes stronger in capacitated spermatozoa followed by a decrease in acrosome reacted sperm. In different cases of semen pathology (oligozoospermia, asthenozoospermia and teratozoospermia) fluorescent signals in the neck and mid-piece are in punctate manner whereas in normozoospermia they were uniformly distributed. The expression area of tACE the neck and mid-piece was decreased in ejaculated and capacitated sperm from pathological semen samples compared to normospermia. Significant positive correlation was established between tACE area and progressive sperm motility, whereas with immotile sperm the correlation was negative. Our data suggest that proper distribution of tACE in the neck and mid-piece is required for normal sperm motility that could be used as a novel biomarker for male infertility.

Physiological implications of COVID-19 in reproduction: angiotensin-converting enzyme 2 a key player

The COVID-19 outbreak, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), was first identified in China, and it has quickly become a global threat to public health due to its rapid rate of transmission and fatalities. Angiotensin-converting enzyme 2 (ACE2) has been identified as a receptor that mediates the entry of SARS-CoV-2 into human cells, as in the case of severe acute respiratory syndrome coronavirus (SARS-CoV). Several studies have reported that ACE2 expression is higher in Leydig, Sertoli and seminiferous ductal cells of males, as well as in ovarian follicle cells of females, suggesting possible potential pathogenicity of the coronavirus in the reproductive system. Higher ACE2 expression in the human placenta and reports of vertical transmission of SARS-CoV-2 among clinical cases have increased the relevance of further studies in this area. This review focuses on the interaction between SARS-CoV-2 and the ACE2 receptor and speculates on the mechanistic interplay in association with male and female reproductive physiology. In addition, based on the available literature, we discuss the alleged sex differences in terms of the infectivity of SARS-CoV-2, which is claimed greater among males, and further explore the physiological role of ACE2 and 17β-oestradiol for the same.

Predicted gene 31453 (Gm31453) and the gene encoding carboxypeptidase A5 (Cpa5) are not essential for spermatogenesis and male fertility in the mouse

Numerous long non-coding (lnc) RNAs are highly enriched or exclusively expressed in the mammalian testis, even in spermatids. Spermatid perinuclear RNA-binding protein (STRBP) can bind many RNAs, and loss of STRBP impairs male fertility. However, the functions of lncRNAs interacting with STRBP are unknown. In this study, the roles of one STRBP-interacting lncRNA, namely predicted gene 31453 (Gm31453), and its potential target gene encoding carboxypeptidase A5 (Cpa5) in spermatogenesis were determined using gene-knockout (KO) mice. Gm31453 and Cpa5 are located adjacent to each other on the same chromosome and are highly expressed in the testis. Gm31453 and Cpa5 are primarily expressed from secondary spermatocytes to elongated spermatids, implying their involvement in spermiogenesis. Although deletion of Gm31453 disturbed the expression of both its target and interacting gene, as indicated by decreased Cpa5 and increased Strbp mRNA levels, both Gm31453- and Cpa5-KO mice showed normal spermatogenesis and fertility, and had no detectable abnormalities in terms of testicular and epididymal development, sperm production morphology or motility, pregnancy rate or litter size. Thus, Gm31453 and Cpa5 are dispensable for spermatogenesis and male fertility in mice. Their involvement in spermatogenesis may be a fine-tuning role, regulating gene expression at the molecular level.

Reduced semen quality in patients with testicular cancer seminoma is associated with alterations in the expression of sperm proteins

Testicular cancer seminoma is one of the most common types of cancer among men of reproductive age. Patients with this condition usually present reduced semen quality, even before initiating cancer therapy. However, the underlying mechanisms by which testicular cancer seminoma affects male fertility are largely unknown. The aim of this study was to investigate alterations in the sperm proteome of men with seminoma undergoing sperm banking before starting cancer therapy, in comparison to healthy proven fertile men (control group). A routine semen analysis was conducted before cryopreservation of the samples (n = 15 per group). Men with seminoma showed a decrease in sperm motility (P = 0.019), total motile count (P = 0.001), concentration (P = 0.003), and total sperm count (P = 0.001). Quantitative proteomic analysis identified 393 differentially expressed proteins between the study groups. Ten proteins involved in spermatogenesis, sperm function, binding of sperm to the oocyte, and fertilization were selected for validation by western blot. We confirmed the underexpression of heat shock-related 70 kDa protein 2 (P = 0.041), ubiquinol-cytochrome C reductase core protein 2 (P = 0.026), and testis-specific sodium/potassium-transporting ATPase subunit alpha-4 (P = 0.016), as well as the overexpression of angiotensin I converting enzyme (P = 0.005) in the seminoma group. The altered expression levels of these proteins are associated with spermatogenesis dysfunction, reduced sperm kinematics and motility, failure in capacitation and fertilization. The findings of this study may explain the decrease in the fertilizing ability of men with seminoma before starting cancer therapy.

Regulation of Male Fertility by the Renin-Angiotensin System

The renin-angiotensin system (RAS) is a peptidic system known mainly for its roles in the maintenance of blood pressure and electrolyte and fluid homeostasis. However, several tissues and cells have been described to possess an intrinsic RAS that acts locally through different paracrine and autocrine mechanisms. In the male reproductive system, several components of this system have been observed in various organs and tissues, such as the testes, spermatozoa and seminal fluid. Some functions attributed to this local RAS are maintenance of seminal plasma electrolytes, regulation of steroidogenesis and spermatogenesis, and sperm functions. However, their specific actions in these locations are not fully understood. Therefore, a deep knowledge of the functions of the RAS at both the testicular and seminal levels could clarify its roles in male infertility and sperm physiology, and the different RAS elements could be used to design tools enabling the diagnosis and/or treatment of male infertility.

Human sperm testicular angiotensin-converting enzyme helps determine human embryo quality

Angiotensin-converting enzyme functions in the male reproductive system, but the extent of its function in reproduction is not fully understood. The primary objective of this work was to investigate the relationship between the testicular isoform of angiotensin-converting enzyme present in human spermatozoa and semen parameters, human embryo quality, and assisted reproduction success. A total of 81 semen samples and 635 embryos from couples undergoing oocyte donation cycles at the IVI Bilbao Clinic were analyzed. Semen parameters, embryos quality, and blastocyst development were examined according to the World Health Organization standards and the Spanish Association of Reproduction Biology Studies criteria. The percentage of testicular angiotensin-converting enzyme-positive spermatozoa and the number of molecules per spermatozoon were analyzed by flow cytometry. Both parameters were inversely correlated with human sperm motility. Higher percentages of testicular angiotensin-converting enzyme-positive spermatozoa together with fewer enzyme molecules per spermatozoon were positively correlated with better embryo quality and development. Our results suggest that embryos with a higher implantation potential come from semen samples with higher percentages of testicular angiotensin-converting enzyme-positive cells and fewer enzyme molecules per spermatozoon. Based on these findings, we propose that testicular angiotensin-converting enzyme could be used to aid embryologists in selecting better semen samples for obtaining high-quality blastocysts during in vitro fertilization procedures.

Association Between Polymorphisms in the Angiotensin-Converting Enzyme Gene and Non-Obstructive Azoospermia in the Chinese Han Population from Northeast China

Background

Genetic defects are commonly observed in infertile males, although the majority of cases remain idiopathic. In recent years, the relationship between single-nucleotide polymorphisms (SNPs) and male infertility has received increasing attention. The objective of this study was to explore the relationship between non-obstructive azoospermia (NOA) and single-nucleotide polymorphisms in the angiotensin-converting enzyme gene (ACE) using ligase detection reaction (LDR)–PCR.

Material/Methods

A retrospective study was performed and we screened 4 ACE SNPs (rs4316, rs4331, rs4343, and rs4362) in 121 NOA cases and 256 control subjects by LDR–PCR. The relationship between SNPs and NOA was analyzed.

Results

ACE SNPs were in Hardy-Weinberg equilibrium (P=0.089 for rs4331, P=0.089 for rs4343, P=0.089 for rs4316, and P=0.381 for rs4362). The allelic and genotypic frequencies of the 4 SNPs were not significantly different between cases and controls (P=0.123 for rs4331, P=0.123 for rs4343, P=0.123 for rs4316, and P=0.179 for rs4362). Haplotype analysis showed the existence of 3 haplotypes, TGAC, CAGT, and TGAT, which showed statistical significance of 0.889, 0.889, and 0.781, respectively, between cases and controls.

Conclusions

No significant association was found between ACE SNPs rs4316, rs4331, rs4343, or rs4362 and NOA in the Chinese Han population of Northeast China.

Alterations of Spermatozoa Proteomic Profile in Men with Hodgkin's Disease Prior to Cancer Therapy

Purpose

Hodgkin's disease (HD) is a type of cancer affecting men in the reproductive age with potential consequences on their fertility status. This study aims to analyze sperm parameters, alterations in proteomic profiles and validate selected protein biomarkers of spermatozoa in men with HD undergoing sperm banking before cancer therapy.

Materials and Methods

Semen analysis was carried out in healthy fertile donors (control, n=42), and patients diagnosed with HD (patients, n=38) before cancer therapy. We compared proteomic profiles of spermatozoa from donors (n=3) and patients (n=3) using LTQ-Orbitrap Elite hybrid MS system.

Results

A total of 1,169 proteins were identified by global proteomic in both groups. The ingenuity pathway analysis revealed that differentially expressed proteins involved in capacitation, acrosome reaction, binding of sperm to the zona pellucida, sperm motility, regulation of sperm DNA damage, and apoptosis were significantly downregulated in HD patients. Validation of proteins implicated in sperm fertility potential by Western Blot demonstrated that peroxiredoxin 2 (PRDX 2) was underexpressed (p=0.015), and transferrin (p=0.045) and SERPIN A5 (p=0.010) protein levels were overexpressed in spermatozoa of men with HD.

Conclusions

Findings of this study indicates that the key proteins involved in sperm fertility potential are significantly altered in men with HD, which provides substantial explanation for the observed low sperm quality in HD subjects prior to cancer therapy. Furthermore, our results suggest PRDX 2, transferrin and SERPIN A5 as possible candidate proteins for assessing sperm quality in HD patients prior to cancer therapy.

Seminal plasma proteins as markers of sperm fertility

During ejaculation and deposition in the female genital tract, spermatozoa are exposed to seminal plasma, a mix of secretions primarily from the accessory sex glands. Proteins, which make up the largest contribution to seminal plasma by weight, have been the focus of much interest, in particular the identification of specific proteins both in the plasma and/or found bound to the sperm surface post ejaculation. Global proteomic studies of seminal plasma originating from a range of species over the last 15 years have revealed their hitherto unknown diversity and complexity. Seminal plasma is generally known to aid sperm survival and fertility in a range of species and studies have begun to reveal its link with sperm function and identification, as markers of fertility. This review summarises recent data on proteins found on the sperm surface that originate from seminal plasma and have subsequently been shown to correlate with fertility, with a focus on the pig.

Proteomic analysis of sperm proteins in infertile men with high levels of reactive oxygen species

Oxidative stress is a significant risk factor for male infertility. A pro-oxidant testicular environment may alter the expression profile of functional sperm proteins and result in poor sperm quality. Patients and donors were divided into ROS (-) and ROS (+) groups. Using computational studies, and data mining of available literature on spermatozoa, oxidative stress and proteomics, we identified three core regulatory proteins angiotensin-converting enzyme (ACE), heat-shock protein (Hsp70) family A member 2 (HSPA2) and ribosomal protein subunit 27A (RPS27A) and seven interlink proteins NOS2, SUMO2, UBL4A, FBXO25, MAP3K3, APP and UBC. HSPA2 was validated by Western Blot, while the localisation of ACE, RPS27A, MAP3K3 and APP was identified by immunocytochemistry. The obtained results showed that HSPA2 was 1.2 (ROS+) and 2.1 (ROS-) fold downregulated in spermatozoa from patients with high levels of reactive oxygen species (ROS). ACE and APP were localised in the post-acrosomal region of spermatozoa, whereas RPS27A and MAP3K3 were localised either in the tail or sperm neck area. Our data show that these proteins may play a role in ROS-induced male infertility.

Effects of Dietary Selenium Supplementation on Seminiferous Tubules and SelW, GPx4, LHCGR, and ACE Expression in Chicken Testis

We investigated the effects of dietary selenium (Se) supplementation on the development of chicken testis and the expression of selenoprotein W (SelW), glutathione peroxidase4 (GPx4), luteinizing hormone/choriogonadotropin receptor (LHCGR), and angiotensin converting enzyme (ACE). Sixty roosters were assigned randomly into the control group fed with a basic diet (containing 0.3 mg Se/kg) and the experimental group fed with a diet (containing 0.6 mg Se/kg). The testes were collected individually at age of 6, 9, and 12 weeks. Se was supplemented in chicken feed for 15 days before sampling. The results indicated that dietary Se affected the number of cells in the seminiferous tubules and viability of Sertoli cells in vitro culture. SelW and GPx4 expression in the testes increased significantly in the experimental group compared to that in the control group. LHCGR expression in the testes increased significantly in the experimental group after 12 weeks compared to that in the control group. In contrast, ACE expression was inhibited in the experimental group compared to that in the control group. These results suggest that dietary supplementation with Se improved development of the seminiferous tubules at the cellular level and that SelW, GPx4, LHCGR, and ACE are involved.

Angiotensin II regulation of angiotensin-converting enzymes in spontaneously hypertensive rat primary astrocyte cultures

Angiotensin (Ang) II plays a critical role in cardiovascular and blood pressure regulation. Ang II is produced by angiotensin-converting enzyme (ACE) and it interacts with the Ang AT1 receptor to cause much of its well-known cardiovascular effects. Ang-(1-7) is another active peptide produced by the rennin-angiotensin system. This peptide is produced from Ang I or Ang II by the catalytic activity of ACE2. Ang-(1-7) interacts with the Mas receptor to counteract many of the effects of Ang II. Thus, the ACE2/Ang-(1-7)/Mas axis acts opposite of the ACE/Ang II/AT1 axis. In this study we investigated how Ang II regulates the key enzymes of these axes, ACE and its homolog ACE2, and determined whether they are dysregulated in the hypertensive condition. Brainstem and cerebellum astrocytes isolated from the spontaneously hypertensive rat (SHR) were used in these studies. Ang II effect on the enzymes' mRNA and protein levels was measured using quantitative PCR and western blotting techniques, respectively. Results from this study showed that Ang II up-regulated ACE protein levels, but down-regulated ACE mRNA levels in brainstem and cerebellum astrocytes in both models. Ang II also reduced ACE2 mRNA expression in SHR and Wistar astrocytes isolated from both brain regions. Ang II effects on ACE2 protein were biphasic. In SHR astrocytes, Ang II-mediated ACE2 protein initially increased then decreased at later time points. In contrast, in Wistar astrocytes, Ang II initially decreased ACE2 protein expression, but up-regulated the protein at later time points. The findings of these studies suggest that Ang II has a differential effect on ACE and ACE2 expression. Furthermore, in the SHR model there may be alteration in the ACE/ACE2 balance in a manner that favors increased Ang II generation and decreased Ang-(1-7) production contributing to the hypertensive phenotype observed in this model. The levels of angiotensin (Ang) II depend on the actions of angiotensin-converting enzyme (ACE) and ACE2. We showed in astrocytes isolated from the SHRs that Ang II differentially affects ACE and ACE2 expression. There may be an alteration in the ACE/ACE2 balance favoring Ang II generation. This imbalance may contribute to the hypertensive phenotype observed in this SHR model.

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.

Human sperm devoid of germinal angiotensin-converting enzyme is responsible for total fertilization failure and lower fertilization rates by conventional in vitro fertilization

In conventional in vitro fertilization (IVF), complete failure of fertilization occurs in 5% to 15% of treatments. Although the causes may be unclear, sperm defects appear to be the major contributor. However, a convincing test is not yet available that can predict the risk of fertilization failure. In this study, we found that germinal angiotensin-converting enzyme (gACE) (also called testicular ACE) was undetectable in sperm from patients who had total fertilization failure (TFF) and lower fertilization rates (LFRs) by IVF based on Western blot and indirect immunofluorescence analyses. Additionally, almost all of the patients without gACE on sperm (23 of 25) manifested a TT genotype of the rs4316 single-nucleotide polymorphism of ACE. Overall, our results indicate that the absence of gACE expression is responsible for TFF and LFRs by IVF. The rs4316 polymorphism of ACE might be associated with infertility in those patients. We conclude that sperm lacking gACE may be recognized before commencing IVF and that the patients may be directed instead to consider intracytoplasmic sperm injection.

Identification of differentially expressed proteins in fresh and frozen–thawed boar spermatozoa by iTRAQ-coupled 2D LC–MS/MS

Cryodamage is a major problem in semen cryopreservation, causing changes in the levels of proteins that influence the function and motility of spermatozoa. In this study, protein samples prepared from fresh and frozen–thawed boar spermatozoa were compared using the isobaric tags for relative and absolute quantification (iTRAQ) labeling technique coupled to 2D LC–MS/MS analysis. A total of 41 differentially expressed proteins were identified and quantified, including 35 proteins that were present at higher levels and six proteins that were present at lower levels in frozen–thawed spermatozoa by at least a mean of 1.79-fold (P<0.05). On classifying into ten distinct categories using bioinformatic analysis, most of the 41 differentially expressed proteins were found to be closely relevant to sperm premature capacitation, adhesions, energy supply, and sperm–oocyte binding and fusion. The expression of four of these proteins, SOD1, TPI1, ODF2, and AKAP3, was verified by western blot analysis. We propose that alterations in these identified proteins affect the quality of cryopreserved semen and ultimately lower its fertilizing capacity. This is the first study to compare protein levels in fresh and frozen–thawed spermatozoa using the iTRAQ technology. Our preliminary results provide an overview of the molecular mechanisms of cryodamage in frozen–thawed spermatozoa and theoretical guidance to improve the cryopreservation of boar semen.

Angiotensin-converting enzymes play a dominant role in fertility

According to the World Health Organization, infertility, associated with metabolic syndrome, has become a global issue with a 10%-20% incidence worldwide. An accumulating body of evidence has shown that the renin-angiotensin system is involved in the fertility problems observed in some populations. Moreover, alterations in the expression of angiotensin-converting enzyme-1, angiotensin-converting enzyme-2, and angiotensin-converting enzyme-3 might be one of the most important mechanisms underlying both female and male infertility. However, as a pseudogene in humans, further studies are needed to explore whether the abnormal angiotensin-converting enzyme-3 gene could result in the problems of human reproduction. In this review, the relationship between angiotensin-converting enzymes and fertile ability is summarized, and a new procedure for the treatment of infertility is discussed.

In Vitro fertilization failure of normozoospermic men: search for a lack of testicular isozyme of angiotensin-converting enzyme

Background

Angiotensin converting enzyme (ACE) is a metalloprotease with two isoforms. The somatic isoform is a key component of the renin-angiotensin system; its main function is to hydrolyse angiotensin I into angiotensin II. The germinal or testicular isoform (tACE) located at the plasma membrane of the spermatozoa, plays a crucial role in the spermatozoa-oocyte interaction during in vivo fertilization, in rodents. Disruption of the tACE in mice has revealed that homozygous male tACE−/− sire few pups despite mating normally. Few spermatozoa from these tACE−/− mice are bound to the zona pellucida (ZP) despite normal semen parameters. Based on these findings in mice models, we hypothesized that some infertile men that have the same phenotype as the tACE−/− mice, ie normal semen parameters and a lack of sperm bind to the ZP in vitro, may have a tACE defect.

Methods

Twenty four men participated to this study. The case subjects (n = 10) had normal semen parameters according to the WHO guidelines (WHO 1999) but a total in vitro fertilization failure with absence of sperm fixation to the ZP. The control subjects (n = 14) also had normal semen parameters and a normal fertilization rate ≥65%. We investigated the tACE expression in spermatozoa by Western-Blot and performed a DNA sequencing of the tACE gene.

Results

Three case-subjects and one control-subject had no tACE expression. There were no statistic differences between the two groups. No mutation was detected in the tACE DNA sequence.

Conclusions

Our results didn’t show any involvement of tACE in human fertilization especially in ZP binding.

Angiotensin-converting enzyme inhibitor does not suppress renal angiotensin II levels in angiotensin I-infused rats

Angiotensin II (Ang II) infusion into rats elevates local angiotensin II levels through an AT1 receptor-dependent pathway in the kidney. We examined whether treatment with an angiotensin-converting enzyme (ACE) inhibitor, temocapril, or an AT1-receptor blocker, olmesartan, prevented elevation of Ang II levels in the kidney of angiotensin I (Ang I)-infused rats. Rats were infused with Ang I (100 ng/min) and treated with temocapril (30 mg/kg per day, n = 10) or olmesartan (10 mg/kg per day, n = 9) for 4 weeks. Ang I infusion significantly elevated blood pressure compared with vehicle-infused rats (n = 6). Treatment with temocapril or olmesartan suppressed Ang I-induced hypertension. Temocapril suppressed both plasma and renal ACE activity. Ang I infusion increased Ang II content in the kidney. Interestingly, temocapril failed to reduce the level of Ang II in the kidney, while olmesartan markedly suppressed an increase in renal Ang II levels. These results suggest a limitation of temocapril and a benefit of olmesartan to inhibit the renal renin-angiotensin system and suggest the possible existence of an ACE inhibitor-insensitive pathway that increases Ang II levels in rat kidney.

ACE gene insertion/deletion polymorphism seminal associations in infertile men

PURPOSE

We assessed seminal associations of the ACE gene insertion/deletion polymorphism in infertile men.

MATERIALS AND METHODS

A total of 405 men were investigated, divided into healthy fertile men, and those with asthenozoospermia, asthenoteratozoospermia and oligoasthenoteratozoospermia, respectively. They underwent semen analysis, and assessment of sperm acrosin activity, hypo-osmotic swelling, seminal 8-iso-prostaglandin-F(2α), total antioxidant capacity, α-glucosidase and ACE gene polymorphisms.

RESULT

The ACE insertion/insertion genotype was noted in 182 men, including 76.5% of healthy fertile men, and 47.4%, 39.8% and 17.6% of those with asthenozoospermia, asthenoteratozoospermia and oligoasthenoteratozoospermia, respectively. The ACE insertion/deletion genotype was noted in 133 men, including 13.7% of healthy fertile men, and 42.3%, 27.5% and 47.2% of those with asthenozoospermia, asthenoteratozoospermia and oligoasthenoteratozoospermia, respectively. The ACE deletion/deletion genotype was identified in 90 men, including 9.8% of healthy fertile men, 10.3%, 32.70% and 35.2% of those with asthenozoospermia, asthenoteratozoospermia and oligoasthenoteratozoospermia, respectively. Men with the ACE deletion/deletion and insertion/deletion genotypes showed a significant decrease in sperm count, motility, linear velocity and normal forms, acrosin activity index, hypo-osmotic swelling test and seminal α-glucosidase, and significantly increased seminal 8-iso-prostaglandin-F(2α) than those with the ACE insertion/insertion genotype.

CONCLUSIONS

ACE gene deletion polymorphism is associated with abnormal seminal variables, such that carriers of the ACE deletion/deletion genotype have higher seminal oxidative stress.

A fluorescence-based protocol for quantifying angiotensin-converting enzyme activity

The determination of angiotensin-converting enzyme (ACE) activity represents a useful tool in the study of different health pathologies, such as hypertension. This protocol describes a fluorescent assay for measuring ACE activity in vitro with high precision and sensitivity. The method relies on the ability of ACE to hydrolyse the internally quenched fluorescent substrate o-aminobenzoylglycyl-p-nitro-L-phenylalanyl-L-proline. The generation of the fluorescent product o-aminobenzoylglycine can be continuously monitored, preferably using a microtiter-plate fluorometer, though the use of a conventional cuvette fluorometer would also be possible. The method has important advantages with respect to other assays, because it involves only a one-step reagent, is easy to carry out and allows the analysis of an elevated number of samples in shorter times. It can be completed in one and a half hours. In addition, the fact that all reagents are commercially available allows the rapid introduction of the assay into the laboratory.

Relationship between spermatozoon movement velocity and expression of testicular isoform of angiotensin-converting enzyme on their surface

The expression of testicular isoform of angiotensin-converting enzyme on the surface of human spermatozoa was evaluated by flow cytometry with monoclonal antibodies to epitopes of C-terminal domain of human angiotensin-converting enzyme and the mean path, mean curvilinear and straight-line velocities were determined by computer analysis of spermatozoon movement. A positive correlation between the expression of testicular isoform of angiotensin-converting enzyme on the cell surface and spermatozoon movement velocity was revealed.

Somatic angiotensin converting enzyme in varicocele

The ACE is found as two isozymes in the body. A somatic isozyme found in blood and several other tissues, and a testis-specific isozyme found only in developing spermatids and mature sperm. In this study, we investigated the ACE activity in left spermatic vein blood samples of infertile patients with varicocele and its correlation to spermatologic parameters. The somatic ACE activities were determined in the peripheral and left spermatic vein blood samples from 31 infertile patients who underwent variococelectomy, and 11 fertile control subjects underwent left inguinal herniorraphy. The somatic ACE activity was measured by kinetic spectrophotometric assay. Semen analyses were performed according to WHO guidelines. The mean somatic ACE activities of peripheral and left spermatic veins of the varicocele group were 60.3 +/- 23.0 and 60.2 +/- 23.2 U/L, respectively. In control group, peripheral and left spermatic vein ACE activities were found as 56.8 +/- 17.1 and 56.5 +/- 15.5 U/L, respectively. There was no significant difference between the ACE activity in peripheral and left spermatic vein blood sample from the varicocele and control group. There was no statistically significant correlation between the spermatologic parameters and ACE activities in the spermatic and peripheral vein in both of varicocele and control groups. As a result, it may be suggested that the somatic ACE has no causative role in pathophysiology of varicocele and varicocele related infertility.

Monoclonal antibodies to native mouse angiotensin-converting enzyme (CD143): ACE expression quantification, lung endothelial cell targeting and gene delivery

We demonstrated previously that the monoclonal antibody 9B9 to angiotensin-converting enzyme (ACE), which accumulates very selectively into the rat lung after systemic injection, is a powerful tool for immunotargeting of therapeutic agents or genes to the rat lung vascular bed. Bearing in mind a high research and therapeutic potential of lung targeting via ACE, we obtained a new set of rat monoclonal antibodies to different epitopes of mouse ACE in order to expand this approach to mice. Nine new monoclonal antibodies, recognizing epitopes on the N- and C-domains of catalytically active mouse ACE, were obtained and examined for their efficacy to bind ACE both in vitro and in vivo. This set of monoclonal antibodies was proved to be useful for ACE quantification (by flow cytometry and cell enzyme-linked immunosorbent assay) on the surface of different mouse ACE-expressing cells: endothelial cells, monocytes, macrophages, dendritic cells and spermatozoa. Moreover, gene delivery into mouse ACE-expressing cells using adenoviruses increased 40-fold after redirecting of these viruses to ACE (by coating these viruses with anti-ACE monoclonal antibodies). Radiolabelled (I(125)) monoclonal antibodies specifically accumulated in the mouse lung after systemic injection. Monoclonal antibodies 3G8.17, 4B10.5 and 4B10.17 demonstrated the highest level of lung uptake, 40-50% of injected dose, and high selectivity of lung uptake. Influence of monoclonal antibodies on ACE shedding was negligible, except monoclonal antibody 1D10.11. None of the tested monoclonal antibodies inhibited ACE activity in vitro. In conclusion, a new set of rat monoclonal antibodies to mouse ACE was obtained suitable to study ACE biology in mice and for ACE expression quantification on mouse cells in particular. These monoclonal antibodies also demonstrated highly efficient and selective lung accumulation and thus has the potential for targeting drugs/genes to the pulmonary vasculature in different mouse models of human lung diseases, including numerous knockout models.

Quantitative study of testicular angiotensin-converting enzyme on the surface of human spermatozoa

Expression of testicular angiotensin-converting enzyme on the surface of human spermatozoa was studied by means of flow cytometry with monoclonal antibodies. Expression of testicular angiotensin-converting enzyme on the cell surface depended on functional and morphological characteristics of spermatozoa.

Testicular Isoform of Angiotensin I-Converting Enzyme (ACE, CD143) on the Surface of Human Spermatozoa: Revelation and Quantification Using Monoclonal Antibodies

PROBLEM

The elucidation of the role of angiotensin-converting enzyme (ACE, CD143) in the male fertility has been hampered by the absence of highly specific antibodies to the native testicular isoform (tACE). The quantification of tACE expression on human-ejaculated spermatozoa was performed using a novel panel of monoclonal antibodies (mAbs).

METHOD OF STUDY

The expression of tACE on the surface of live and fixed human spermatozoa was analyzed by flow cytometry and immunocytochemistry using new mAbs to human tACE.

RESULTS

Monoclonal antibodies 1E10 and 4E3 similarly revealed tACE on the surface of live and fixed spermatozoa. The high percentage of tACE-positive spermatozoa (median 81%) was revealed in the swim-up fraction of sperm. Antibody-induced tACE shedding occurs preferentially from live sperm with defective function and/or morphology. Testicular ACE is located on the plasma membrane of the post-acrosomal region, the neck and midpiece of normal spermatozoa, but showed a variable distribution on the defective cells.

CONCLUSIONS

The new mAbs recognizing the C-terminal domain of human ACE are useful tools for quantification of tACE expression on human live and fixed spermatozoa and further adequate analysis of the tACE role in reproduction.

Synthesis and secretion of angiotensin II by the prostate gland in vitro

The renin angiotensin system has been shown to have tissue-related functions that are distinct from its systemic roles. We showed that angiotensin II type 1 (AT1) receptors are present in mammalian sperm, and angiotensin II stimulates sperm motility and capacitation. In addition, angiotensin II is present in human seminal plasma at concentrations higher than found in blood. In testing the possibility that the prostate may be the source of seminal plasma angiotensin II, mRNA coding for angiotensinogen, (pro)renin, and angiotensin-converting enzyme were identified by RT-PCR in rat and human prostate and in prostate LNCaP cells, as well as the angiotensin receptors types 1 and 2 (AT1 and AT2) in human tissues and AT1 in rat. In human tissue, immunocytochemistry showed cellular colocalization of renin with the AT1 receptor in secretory epithelial cells. Confirmation of the capacity of the prostate to secrete angiotensin II was shown by the detection of immunoreactive angiotensin in media removed from rat prostate organ cultures and LNCaP cells. Rat prostate angiotensin secretion was enhanced by dihydrotestosterone, but LNCaP angiotensin was stimulated by estradiol. This stimulation was blocked by tamoxifen. Rat prostate AT1 receptor expression was much greater in prepuberal than in postpuberal rats but was not affected by a low-sodium diet. It was, however, significantly enhanced by captopril pretreatment. These findings all suggest the independence of prostate and systemic renin angiotensin system regulation. The data presented here suggest that the prostate may be a source of the secreted angiotensin II found in seminal plasma.