Leukocytes coincubated with human sperm trigger classic neutrophil extracellular traps formation, reducing sperm motility

Quercetin Protects Goat Sperm Motility by Inhibiting Neutrophil Extracellular Traps and Maintaining Plasma Membrane and Acrosome Integrity

Enhancing or protecting sperm motility has always been a pivotal approach to improving the ewe pregnancy rate. Sperm motility is highly susceptible to the immune status of the reproductive tract. Neutrophil extracellular traps (NETs) have been demonstrated to capture sperm and impair its motility in human, swine, and goat species. Quercetin is a flavonoid derived from Cuscuta Chinensis Lam., which can protect sperm from oxidative damage. In this study, we investigated whether inflammation decreases sperm motility and tried to clarify the potential protective mechanism of quercetin on goat sperm motility. Sperm-triggered NETs were analyzed by immunofluorescence analysis. Sperm acrosome integrity was detected by using giemsa staining. Quercetin exhibited no cytotoxicity towards sperm and PMNs within the concentration range of 20-80 μM. PMNs impaired both the survival rate and rapid linear motility of sperm, while quercetin significantly enhanced these parameters. PMNs captured sperm through NETs composed of DNA, citrullinated histone 3 (citH3), and neutrophil elastase (NE); however, quercetin effectively inhibited the release of sperm-stimulated NETs. The stimulation of PMNs with sperm resulted in a significant increase in levels of ROS and MDA, which decreased by quercetin. Moreover, PMNs caused integrity violation to both the plasma membrane and acrosome in sperm; this effect was significantly alleviated by quercetin. In conclusion, quercetin effectively ameliorated PMN-reduced sperm motility through the inhibition of NETs and oxidative stress, and preserving sperm plasma membrane and acrosome integrity, thereby providing preliminary insights into the underlying mechanisms and theoretical support for the development of potential sperm protectors.

Transmission electron microscopy reveals the presence of SARS-CoV-2 in human spermatozoa associated with an ETosis-like response

BACKGROUND

Severe acute syndrome coronavirus 2 can invade a variety of tissues, including the testis. Even though this virus is scarcely found in human semen polymerase chain reaction tests, autopsy studies confirm the viral presence in all testicular cell types, including spermatozoa and spermatids.

OBJECTIVE

To investigate whether the severe acute syndrome coronavirus 2 is present inside the spermatozoa of negative polymerase chain reaction-infected men up to 3 months after hospital discharge.

MATERIALS AND METHODS

This cross-sectional study included 13 confirmed moderate-to-severe COVID-19 patients enrolled 30-90 days after the diagnosis. Semen samples were obtained and examined with real-time polymerase chain reaction for RNA detection and by transmission electron microscopy.

RESULTS

In moderate-to-severe clinical scenarios, we identified the severe acute syndrome coronavirus 2 inside spermatozoa in nine of 13 patients up to 90 days after discharge from the hospital. Moreover, some DNA-based extracellular traps were reported in all studied specimens.

DISCUSSION AND CONCLUSION

Although severe acute syndrome coronavirus 2 was not present in the infected men's semen, it was intracellularly present in the spermatozoa till 3 months after hospital discharge. The Electron microscopy (EM) findings also suggest that spermatozoa produce nuclear DNA-based extracellular traps, probably in a cell-free DNA-dependent manner, similar to those previously described in the systemic inflammatory response to COVID-19. In moderate-to-severe cases, the blood-testes barrier grants little defence against different pathogenic viruses, including the severe acute syndrome coronavirus 2. The virus could also use the epididymis as a post-testicular route to bind and fuse to the mature spermatozoon and possibly accomplish the reverse transcription of the single-stranded viral RNA into proviral DNA. These mechanisms can elicit extracellular cell-free DNA formation. The potential implications of our findings for assisted conception must be addressed, and the evolutionary history of DNA-based extracellular traps as preserved ammunition in animals' innate defence might improve our understanding of the severe acute syndrome coronavirus 2 pathophysiology in the testis and spermatozoa.

Progesterone promotes CXCl2-dependent vaginal neutrophil killing by activating cervical resident macrophage-neutrophil crosstalk

Vaginal infections in women of reproductive age represent a clinical dilemma with significant socioeconomic implications. The current understanding of mucosal immunity failure during early pathogenic invasions that allows the pathogen to grow and thrive is far from complete. Neutrophils infiltrate most tissues following circadian patterns as part of normal repair, regulation of microbiota, or immune surveillance and become more numerous after infection. Neutrophils are responsible for maintaining vaginal immunity. Specific to the vagina, neutrophils continuously infiltrate at high levels, although during ovulation, they retreat to avoid sperm damage and permit reproduction. Here we show that, after ovulation, progesterone promotes resident vaginal macrophage-neutrophil crosstalk by upregulating Yolk sac early fetal organs (FOLR2+) macrophage CXCl2 expression, in a TNFA-patrolling monocyte-derived macrophage-mediated (CX3CR1hiMHCIIhi-mediated) manner, to activate the neutrophils' capacity to eliminate sex-transmitted and opportunistic microorganisms. Indeed, progesterone plays an essential role in conciliating the balance between the commensal microbiota, sperm, and the threat of pathogens because progesterone not only promotes a flurry of neutrophils but also increases neutrophilic fury to restore immunity after ovulation to thwart pathogenic invasion after intercourse. Therefore, modest progesterone dysregulations could lead to a suboptimal neutrophilic response, resulting in insufficient mucosal defense and recurrent unresolved infections.

Cytotoxic Oxidative Stress Effects of Neutrophil Extracellular Traps' Components on Cattle Spermatozoa

Bovine spermatozoa are highly susceptible to oxidative stress (OS), and it is known to affect their cellular functions. The main leukocyte producers of reactive oxygen species (ROS) in mammalian semen are polymorphonuclear neutrophils (PMN). PMN activation can result in the formation of neutrophil extracellular traps (NETs), which have been shown to affect the motility and function of spermatozoa. However, OS effects on bull spermatozoa derived from individual NETs components have not been investigated. The hypothesis of this study was that specific NETs components might generate OS on bull spermatozoa. Bovine sperm cells were incubated with five NETs-associated molecules, including 30 μg/mL histone 2A (H2A), neutrophil elastase (NE), 1 μg/mL myeloperoxidase (MPO), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), for a time course ranging from 15 to 240 min. Fluorescence microscopy was used to evaluate the coincubation of bovine PMN and sperm cells. Within 15 min, H2A, NE, and LL-37 caused membrane disruption, while MPO and Cat-G caused OS on bull spermatozoa after 1 h of coincubation. NET formation was observed within 15 min of coincubation in co-cultures of bovine PMN/sperm cells. This study is the first to report on the role of cytotoxic OS effects caused by NETs-derived components in bovine sperm in vitro.

Effects of Reactive Oxygen and Nitrogen Species on Male Fertility

Significance: In recent decades, male fertility has been severely reduced worldwide. The causes underlying this decline are multifactorial, and include, among others, genetic alterations, changes in the microbiome, and the impact of environmental pollutants. Such factors can dysregulate the physiological levels of reactive species of oxygen (ROS) and nitrogen (RNS) in the patient, generating oxidative and nitrosative stress that impairs fertility. Recent Advances: Recent studies have delved into other factors involved in the dysregulation of ROS and RNS levels, such as diet, obesity, persistent infections, environmental pollutants, and gut microbiota, thus leading to new strategies to solve male fertility problems, such as consuming prebiotics to regulate gut flora or treating psychological conditions. Critical Issues: The pathways where ROS or RNS may be involved as modulators are still under investigation. Moreover, the extent to which treatments can rescue male infertility as well as whether they may have side effects remains, in most cases, to be elucidated. For example, it is known that prescription of antioxidants to treat nitrosative stress can alter sperm chromatin condensation, which makes DNA more exposed to ROS and RNS, and may thus affect fertilization and early embryo development. Future Directions: The involvement of extracellular vesicles, which might play a crucial role in cell communication during spermatogenesis and epididymal maturation, and the relevance of other factors such as sperm epigenetic signatures should be envisaged in the future.

Effect of different sperm populations on neutrophils extracellular traps (NETs) formation in cattle

In cattle, clinical and subclinical inflammation in the bovine female reproductive tract (FRT) significantly reduces fertility. PMN participate in this FRT-associated inflammation by eliminating pathogens by eliciting various defense mechanisms, with the release of neutrophil extracellular traps NETs) being the latest process discovered. Consistently, human-, bovine- and porcine-derived spermatozoa induce release of NETs in exposed PMN of the same species origin, and thereby decreasing sperm motility through NETs-mediated entrapment. The release of NETs in the presence of different sperm sub-populations is evaluated in this work. Cryopreserved bovine sperm were selected and different sperm populations were used: viable sperm, sperm with oxidative stress, capacitated sperm, and sperm with loss of viability. Isolated PMN of dairy cows were co-incubated with these sperm populations for 4 h. Neutrophil elastase (NE) and DNA were detected by fluorescence microscopy analysis. It was noted that exposed bovine PMN released NETs in the presence of sperm. Moreover, sperm-triggered NETosis resulted different phenotypes of NETs, i. e. spread NETs (sprNETs), diffused NETs (diffNETs) and aggregated NETs (aggNETs). Viable/motile spermatozoa induced a higher proportion of NETotic cells at 15, 60 and 120 min in comparison to controls. In conclusion, all bovine sperm populations in co-culture with PMN generated NETs extrusion while viable sperm activated NETotic cells to a greater extent. With this being an early event in the activation of bovine PMN.

Immune Regulation of Seminal Plasma on the Endometrial Microenvironment: Physiological and Pathological Conditions

Seminal plasma (SP) accounts for more than 90% of semen volume. It induces inflammation, regulates immune tolerance, and facilitates embryonic development and implantation in the female reproductive tract. In the physiological state, SP promotes endometrial decidualization and causes changes in immune cells such as macrophages, natural killer cells, regulatory T cells, and dendritic cells. This leads to the secretion of cytokines and chemokines and also results in the alteration of miRNA profiles and the expression of genes related to endometrial tolerance and angiogenesis. Together, these changes modulate the endometrial immune microenvironment and contribute to implantation and pregnancy. However, in pathological situations, abnormal alterations in SP due to advanced age or poor diet in men can interfere with a woman's immune adaptation to pregnancy, negatively affecting embryo implantation and even the health of the offspring. Uterine pathologies such as endometriosis and endometritis can cause the endometrium to respond negatively to SP, which can further contribute to pathological progress and interfere with conception. The research on the mechanism of SP in the endometrium is conducive to the development of new targets for intervention to improve reproductive outcomes and may also provide new ideas for semen-assisted treatment of clinical infertility.

Sperm induce macrophage extracellular trap formation via phagocytosis-dependent mechanism

Infertility is a public health concern worldwide. Asthenozoospermia is a common cause of male infertility and is characterized by decreased motility. Sperm motility ensures that sperm migrate to complete fertilization. Macrophages are an essential component of innate immunity in the female reproductive tract. Macrophage extracellular traps are induced by various microorganisms to capture and mediate the clearance of microorganisms. The relationship between sperm and macrophage extracellular traps is unclear. The human monocyte leukemia (THP-1) cells differentiated by phorbol myristate acetate (PMA) are widely used as surrogate of human macrophages. This study investigated sperm-induced macrophage extracellular trap formation and clarified some of the mechanisms affecting macrophage extracellular trap production. Sperm-induced macrophage extracellular traps were visualized and components of macrophage extracellular traps were identified by immunofluorescence analyses and scanning electron microscopy. By inhibiting macrophage extracellular trap production and macrophage phagocytosis, the relationship between macrophage phagocytosis and macrophage extracellular trap production was analyzed. Sperm could trigger PMA-differentiated THP-1 macrophages to produce extracellular traps. Sperm-triggered macrophage extracellular traps are dependent on phagocytosis and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Sperm from asthenozoospermia donors are more likely to be phagocytosed by macrophages than sperm from healthy donors, which induce more macrophage extracellular trap release. These data confirm the phenomenon and partial mechanism of sperm-induced macrophage extracellular trap formation in vitro. These may partly provide evidence to explain the mechanisms of clearing abnormally morphological or hypomotile sperm in the female reproductive tract and the rationale for the decreased probability of successful fertilization in asthenozoospermia.

Immune responses in the uterine mucosa: clues for vaccine development in pigs

The immune system in the upper reproductive tract (URT) protects against sexually transmitted pathogens, while at the same time providing immune tolerance responses against allogenic sperm and the developing fetus. The uterine environment is also responsive to hormonal variations during the estrus cycle, although the most likely timing of exposure to pathogens is during estrus and breeding when the cervix is semi-permissive. The goal for intrauterine immunization would be to induce local or systemic immunity and/or to promote colostral/lactogenic immunity that will passively protect suckling offspring. The developing fetus is not the vaccine target. This minireview article focuses on the immune response induced in the pig uterus (uterine body and uterine horns) with some comparative references to other livestock species, mice, and humans.

Mitochondrial Dynamics as Potential Modulators of Hormonal Therapy Effectiveness in Males

Worldwide the incidence of andrological diseases is rising every year and, together with it, also the interest in them is increasing due to their strict association with disorders of the reproductive system, including impairment of male fertility, alterations of male hormones production, and/or sexual function. Prevention and early diagnosis of andrological dysfunctions have long been neglected, with the consequent increase in the incidence and prevalence of diseases otherwise easy to prevent and treat if diagnosed early. In this review, we report the latest evidence of the effect of andrological alterations on fertility potential in both young and adult patients, with a focus on the link between gonadotropins' mechanism of action and mitochondria. Indeed, mitochondria are highly dynamic cellular organelles that undergo rapid morphological adaptations, conditioning a multitude of aspects, including their size, shape, number, transport, cellular distribution, and, consequently, their function. Since the first step of steroidogenesis takes place in these organelles, we consider that mitochondria dynamics might have a possible role in a plethora of signaling cascades, including testosterone production. In addition, we also hypothesize a central role of mitochondria fission boost on the decreased response to the commonly administrated hormonal therapy used to treat urological disease in pediatric and adolescent patients as well as infertile adults.

Vaginal neutrophil infiltration is contingent on ovarian cycle phase and independent of pathogen infection

The mucosa of the female reproductive tract must reconcile the presence of commensal microbiota and the transit of exogenous spermatozoa with the elimination of sexually transmitted pathogens. In the vagina, neutrophils are the principal cellular arm of innate immunity and constitute the first line of protection in response to infections or injury. Neutrophils are absent from the vaginal lumen during the ovulatory phase, probably to allow sperm to fertilize; however, the mechanisms that regulate neutrophil influx to the vagina in response to aggressions remain controversial. We have used mouse inseminations and infections of Neisseria gonorrhoeae, Candida albicans, Trichomonas vaginalis, and HSV-2 models. We demonstrate that neutrophil infiltration of the vaginal mucosa is distinctively contingent on the ovarian cycle phase and independent of the sperm and pathogen challenge, probably to prevent sperm from being attacked by neutrophils. Neutrophils extravasation is a multi-step cascade of events, which includes their adhesion through selectins (E, P and L) and integrins of the endothelial cells. We have discovered that cervical endothelial cells expressed selectin-E (SELE, CD62E) to favor neutrophils recruitment and estradiol down-regulated SELE expression during ovulation, which impaired neutrophil transendothelial migration and orchestrated sperm tolerance. Progesterone up-regulated SELE to restore surveillance after ovulation.

Interaction of sperm cells with the female reproductive tract in cattle: Focus on neutrophil extracellular trap formation

After insemination of cows, either naturally or artificially, the deposition of semen into the vagina or uterus results in an immune reaction which is based on polymorphonuclear neutrophil activity. Sperm must be resistant to immune system actions of the female for an adequate time to allow fertilization to occur. Neutrophils, however, either directly phagocytize sperm through cell-cell attachment or entrap sperm cells in neutrophil extracellular traps (NETs), structures consisting of neutrophil nuclear DNA and associated proteins. In this review article, the interaction of neutrophils and sperm cells in t cattle will be described, with a special focus on the formation of neutrophil extracellular traps (NETs).

High Presence of NETotic Cells and Neutrophil Extracellular Traps in Vaginal Discharges of Women with Vaginitis: An Exploratory Study

Infectious vaginitis is a microbiological syndrome of great importance in public health that affects millions of women worldwide. However, no studies have explored the phenomenon of the production of the neutrophil extracellular traps (NETs) that are released into the female reproductive tract in these pathologies. This study aimed to determine the presence of NETosis in vaginal discharges of women with bacterial vaginosis, candidiasis, and trichomoniasis by characterizing NETs. Extracellular DNA with neutrophil elastase and citrullinated histones was identified to confirm the NET components (n = 10). The concentration, phenotypes of NETs, and number of NETotic cells were determined. The results showed an increase in NETotic cells in women with Candida albicans (CA) and Trichomonas vaginalis (TV) and an increase in NETs in TV-induced vaginitis. Samples of CA- and TV-infected women showed different NET phenotypes (diffNETs, sprNETs, and aggNETs); diffNETs were found in high concentrations in samples with CA and were increased in three types of NETs in TV infections. Samples with intermediate microbiota and bacterial vaginosis showed increased NETotic cells while the intermediate microbiota presented a higher concentration of NETs. Therefore, alterations in the microbiota and the presence of fungal and parasitic infections are important stimuli for the activation and induction of NETosis, and their cytotoxic effects could enhance tissue damage.

Bacteriospermia - A formidable player in male subfertility

Bacterial colonization of male reproductive tissues, cells, and fluids, and the subsequent impact of bacteria on the sperm architecture, activity, and fertilizing potential, has recently gained increased attention from the medical and scientific community. Current evidence strongly emphasizes the fact that the presence of bacteria in semen may have dire consequences on the resulting male fertility. Nevertheless, the molecular basis underlying bacteriospermia-associated suboptimal semen quality is sophisticated, multifactorial, and still needs further understanding. Bacterial adhesion and subsequent sperm agglutination and immobilization represent the most direct pathway of sperm-bacterial interactions. Furthermore, the release of bacterial toxins and leukocytic infiltration, associated with a massive outburst of reactive oxygen species, have been repeatedly associated with sperm dysfunction in bacteria-infested semen. This review serves as a summary of the present knowledge on bacteriospermia-associated male subfertility. Furthermore, we strived to outline the currently available methods for assessing bacterial profiles in semen and to outline the most promising strategies for the prevention and/or management of bacteriospermia in practice.

Adverse Effects of Single Neutrophil Extracellular Trap-Derived Components on Bovine Sperm Function

Neutrophil extracellular traps (NETs) play a key role in fertilisation by eliminating microorganisms and entrapping spermatozoa in the female reproductive tract (FRT). The deleterious effects of NETs on spermatozoa have been previously described; however, individual exposure to NET-derived components in bull spermatozoa has not been explored. The aim of this study was to evaluate the effects of the main NET-derived proteins, histone 2A (H2A), neutrophil elastase (ELA), myeloperoxidase (MPO), pentraxin 3 (PTX), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), at concentrations of 1, 10, and 30 μg/mL, on sperm parameters. Sperm were selected and incubated with different NET-derived proteins for 4 h. Membrane and acrosome integrity, lipoperoxidation, and membrane phospholipid disorders were also evaluated. Bovine polymorphonuclear neutrophil (PMN)/sperm co-cultures were evaluated by scanning electron microscopy and immunofluorescence. All NET-derived proteins/enzymes resulted in a reduction in membrane integrity, acrosome integrity, and lipoperoxidation at a concentration of 30 μg/mL. Bovine PMN/sperm co-cultures showed marked NET formation in the second hour. In conclusion, all NET-derived proteins/enzymes exerted cytotoxic effects on bull sperm, and this effect should be considered in future investigations on the uterine microenvironment and the advancement of spermatozoa in the FRT.

Addition of Reduced Glutathione (GSH) to Freezing Medium Reduces Intracellular ROS Levels in Donkey Sperm

In donkeys, the use of frozen-thawed sperm for artificial insemination (AI) leads to low fertility rates. Furthermore, donkey sperm produce a large amount of reactive oxygen species (ROS), and post-AI inflammation induces the formation of neutrophil extracellular traps (NETosis), which further generates many more ROS. These high ROS levels may induce lipid peroxidation in the sperm plasma membrane, thus affecting its integrity. Enzymatic and non-enzymatic antioxidants, mainly found in the seminal plasma (SP), are responsible for maintaining the redox balance. However, this fluid is removed prior to cryopreservation, thereby exposing sperm cells to further oxidative stress. The exogenous addition of antioxidants to the freezing medium can reduce the detrimental effects caused by ROS generation. Therefore, the aim of this study was to evaluate how the addition of different reduced glutathione (GSH) concentrations (control, 2 mM, 4 mM, 6 mM, 8 mM, and 10 mM) to fresh sperm affect their cryotolerance. Total and progressive motility, kinematic parameters and motile sperm subpopulations were significantly (p < 0.05) different from the control in treatments containing 8 mM and 10 mM GSH, but not at lower concentrations. Plasma and acrosome membrane integrity, mitochondrial membrane potential (MMP) and intracellular superoxide levels (O₂⁻) were not affected (p > 0.05) by any GSH concentration. Interestingly, however, the addition of 8 mM or 10 mM GSH reduced (p < 0.05) the percentages of viable sperm with high overall ROS levels compared to the control. In conclusion, frozen-thawed donkey sperm are able to tolerate high GSH concentrations, which differs from what has been observed in other species. This antioxidant capacity suggests that ROS could be important during post-AI and that the impact of using exogenous antioxidants like GSH to improve the sperm resilience to freeze-thawing is limited in this species.

Comparison of the uterine inflammatory response to frozen-thawed sperm from high and low fertility bulls

Some bulls with apparently normal semen quality yield unacceptably low pregnancy rates. We hypothesised that a differential uterine immunological response to sperm from high and low fertility bulls may contribute to these differences. The experimental model used was heifer follicular phase uterine explants incubated with frozen-thawed sperm from high and low fertility bulls (3-5 replicates per experiment). Inflammatory gene expression of IL1A, IL1B, IL6, TNFA and CXCL8 were assessed by qPCR and IL1-β and IL-8 were quantified in explant supernatants by ELISA. Neutrophil binding affinity to sperm from high and low fertility bulls was also assessed. There was a significant up-regulation of IL1A, IL1B and TNFA from frozen-thawed sperm, irrespective of fertility status, compared to the unstimulated control. This response was confirmed at the protein level, with an increase of IL-1β and IL-8 protein concentrations by 5 and 2.7 fold, respectively (P < 0.05). Although no significant differences in the inflammatory response at the gene or protein level were evident between high and low fertility bulls, more sperm from low compared to high fertility bulls bound to neutrophils (P < 0.05). Using bulls of unknown fertility, cauda epididymal sperm (CES) plus seminal plasma (SP) upregulated IL6 (P < 0.05) but there was no upregulation of any inflammatory gene expression for CES alone. Overall, this ex vivo study demonstrated an upregulation of inflammatory gene expression in the uterus in response to frozen-thawed bull sperm. While there was no difference between sperm from high and low fertility bulls, there was a greater binding affinity of low fertility sperm by neutrophils.

Extracellular Reactive Oxygen Species (ROS) Production in Fresh Donkey Sperm Exposed to Reductive Stress, Oxidative Stress and NETosis

Jenny shows a large endometrial reaction after semen influx to the uterus with a large amount of polymorphonuclear neutrophils (PMN) migrating into the uterine lumen. PMN act as a sperm selection mechanism through phagocytosis and NETosis (DNA extrudes and, together with proteins, trap spermatozoa). While a reduced percentage of spermatozoa are phagocytosed by PMN, most are found to be attached to neutrophil extracellular traps (NETs). This selection process together with sperm metabolism produces a large amount of reactive oxygen species (ROS) that influence the reproductive success. The present study aimed to determine the extracellular ROS production in both sperm and PMN. With this purpose, (1) donkey sperm were exposed to reductive and oxidative stresses, through adding different concentrations of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂), respectively; and (2) PMN were subjected to NETosis in the presence of the whole semen, sperm, seminal plasma (SP) or other activators such as formyl-methionyl-leucyl-phenylalanine (FMLP). Extracellular ROS production (measured as H₂O₂ levels) was determined with the Amplex^® Red Hydrogen Peroxide/Peroxidase Assay Kit. Donkey sperm showed more resilience to oxidative stress than to the reductive one, and GSH treatments led to greater H₂O₂ extracellular production. Moreover, not only did SP appear to be the main inducer of NETosis in PMN, but it was also able to maintain the extracellular H₂O₂ levels produced by sperm and NETosis.

Bovine sperm samples induce different NET phenotypes in a NADPH oxidase-, PAD4-, and Ca++-dependent process†

Deposition of sperm during artificial insemination in the bovine female reproductive tract results in early host innate immune reactions of polymorphonuclear neutrophils (PMNs). Furthermore, sperm-mediated neutrophil extracellular trap (NET) formation (NETosis) was recently reported to occur in different mammalian species, including humans. We, here, investigated the interactions of bovine PMN with different semen-derived samples and analyzed in more depth molecular aspects of this effector mechanism. Overall, confrontation of PMN with sperm/cell preparation (SCP) resulted in a rapid and dose-dependent NET formation leading to effective spermatozoa entrapment. Thereby, spermatozoa induced different phenotypes of NETs. Immunostaining analyses revealed the presence of histones (H3), neutrophil elastase (NE), and pentraxin (PTX) in sperm-triggered NET structures. Fresh SCP strongly induced NETosis than frozen-thawed ones. The level of NETosis was not related to spermatozoa viability. SCP as well as purified sperm cells (SCs) and supernatant (SN) induce NETosis, although the reaction in SC was lower. Enhanced levels of oxygen consumption and proton leak in PMN revealed sperm SNs but not purified SCs as PMN activators. Functional inhibition experiments revealed sperm-triggered NETosis as an NADPH oxidase- and peptidylarginine deiminase 4-dependent process and proved to be dependent on intra- and extracellular Ca++ influxes while myeloperoxidase activity and as ERK1/2- and PI3K-related signaling pathways did not seem to play a pivotal role in this effector mechanism. From these findings, we speculate that sperm-derived NETosis might also occur in vivo during artificial insemination and might therefore play a role related to reduced fertility.

Intra-nasal administration of sperm head turns neutrophil into reparative mode after PGE1- and/or Ang II receptor-mediated phagocytosis followed by expression of sperm head's coding RNA

Having played homeostatic role, the immune system maintains the integrity of the body. Such a characteristic makes immune system as an attractive candidate for resolution of inflammatory disease followed by tissue repair. As first responder cells, neutrophils direct immune response playing key role in tissue remodeling. Previous studies revealed that sperm attracts neutrophils and promotes uterine remodeling suitable for fetus growth. Accordingly, sperm and more efficiently sperm head had remodeling effects on damaged brain in Alzheimer's disease (AD) model. To further reveal the mechanism, two kinds of in vivo study, including kinetic study and inhibition of neutrophil phagocytosis on AD model, as well as in vitro study using co-culture of neutrophil and sperm head were performed. Kinetic study revealed that sperm head recruited neutrophil to nasal mucosa similar to that of uterus and sperm head-phagocytizing neutrophils acquired new activation status comparing to control. In vitro study also demonstrated that sperm head-phagocytizing neutrophils acquire new activation status and express coding RNAs of sperm head. Accordingly, inhibition of neutrophil phagocytic activity abrogated therapeutic effects of sperm head. Neutrophils activation status is important in the fate of inflammatory process. Modulation but not suppression of neutrophils helps remodeling and repair of damaged tissue. Sperm head is an intelligent cell and not just a simple particle to remove by phagocytosis but instead can program neutrophils and consequently immune response into reparative mode after phagocytosis.

Myeloperoxidase inhibitor AZD5904 enhances human sperm function in vitro

STUDY QUESTION

Does AZD5904, a myeloperoxidase inhibitor (MPOi), have any effect on human sperm function in vitro?

SUMMARY ANSWER

AZD5904 improves sperm function in an in vitro model of oxidative stress (OS) and potentially offers a novel treatment approach for male infertility.

WHAT IS KNOWN ALREADY

Male infertility is an underlying or contributory cause in half of all couples experiencing difficulties conceiving, yet there is currently no effective treatment or cure. OS is a common pathology in a significant proportion of infertile men. It can negatively affect sperm motility and the ability to fertilize a mature oocyte, as well as DNA integrity, and therefore represents an attractive target for therapeutic intervention.

STUDY DESIGN, SIZE, DURATION

This study included population-based samples from men (23-50 years) attending Ninewells Assisted Conception Unit, Dundee for diagnostic semen analysis, July 2017-September 2018. Semen samples (n = 47) from 45 patients were used.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Neutrophils activated using zymosan were incubated with prepared human spermatozoa for 2 h (T2) and 24 h (T24) to create an in vitro model of OS. Parallel samples were co-incubated with AZD5904, an MPOi, to examine its effects. Sperm motility was assessed by computer-assisted sperm analysis at T2 and T24. Functional motility was assessed by sperm penetration assay. Statistical analysis was performed using GraphPad Prism.

MAIN RESULTS AND THE ROLE OF CHANCE

There was no significant difference in total or progressive sperm motility between any treatment and control groups at T2 or T24. Nonetheless, significant positive effects on sperm function were observed with AZD5904, with 16/45 (35.6%) samples (with both normal and abnormal baseline semen analysis characteristics) displaying a ≥20% increase in sperm penetrated through viscous media (P < 0.003).

LIMITATIONS, REASONS FOR CAUTION

This was an in vitro study.

WIDER IMPLICATIONS OF THE FINDINGS

Treatment with AZD5904 resulted in significant increased sperm penetration in one of three samples treated, which is likely to represent improvement in sperm function required for fertilization. We are now planning a clinical trial to validate these results and hope that this could represent a new treatment for male infertility.

STUDY FUNDING/COMPETING INTEREST(S)

AZD5904 was shared through the AstraZeneca Open Innovation program. The study was funded by AstraZeneca and sponsored by the University of Dundee. Additional funding was provided by Chief Scientist Office/NHS Research Scotland (S.J.M.d.S.). A.W. and H.J.S. are both full time employees of AstraZeneca. A.W. and H.J.S. are inventors on a patent filed by AstraZeneca titled MPOi for use in medicine which includes MPOi for use in the treatment of male infertility (WO 2019/016074 Al). S.J.M.d.S. is Associate Editor of Human Reproduction and Editorial Board member of Reproduction & Fertility. C.L.R.B. is Editor of RBMO and has received lecturing fees from Merck and Ferring and is on the Scientific Advisory Panel for Ohana BioSciences. C.L.R.B. was chair of the World Health Organization Expert Synthesis Group on Diagnosis of Male infertility (2012-2016). C.L.R.B. has a patent WO2013054111 A1 issued. The other authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Swine spermatozoa trigger aggregated neutrophil extracellular traps leading to adverse effects on sperm function

In pigs, the number of PMN in uterus lumen increases within few hours after natural or artificial AI resulting in early PMN-derived innate immune reactions. Sperm-NETs formation was recently reported to occur in various mammalian species. Aim of this study was to investigate direct interactions of boar spermatozoa with swine PMN, the release of sperm-mediated NETs, and to assess NET-derived effects on sperm functionality. Sperm-triggered NETs were visualized by SEM- and immunofluorescence analyses. Sperm-mediated NETosis was confirmed by presence of extruded DNA with global histones and NE. Largest sizes of sperm-mediated aggNETs were detected after 5 h thereby resulting in effective massive sperm entrapment. The number of aggNETs increased from 3 h onwards. Kinetic studies of swine sperm-mediated NETosis showed to be a time-dependent cellular process. In addition, number of NETs-entrapped spermatozoa increased at 3 h of exposure whilst few free spermatozoa were detected after 3 h. Anchored NETs also increased from 3 h onwards. The cytotoxicity of NETs was confirmed by diminution of the total motility and the progressive motility. Spermatozoa membrane integrity and function loss exposed to NETs was confirmed from 3 h. Experiments revealed NETs-derived damaging effects on swine spermatozoa in membrane integrity, motility and functionality. We hypothesize that swine sperm-triggered aggNETs might play a critical role in reduced fertility potential in swine reproductive technique. Thus, aggNETs formation needs to be considered in future studies about uterine environment as well as advance of sperm in the porcine female reproductive tract.

Seminal plasma, and not sperm, induces time and concentration-dependent neutrophil extracellular trap release in donkeys

BACKGROUND

In several mammalian species, acute endometritis driven by the recruitment of polymorphonuclear cells (PMN) occurs in response to semen. These PMNs release DNA to form neutrophil extracellular traps (NETs) in cattle, horse and human, leading to sperm entrapment. While there is no evidence of this phenomenon occurring in donkeys, artificial insemination (AI) with frozen-thawed semen, which results in very poor pregnancy rates, leads to a large PMN recruitment to the uterus.

OBJECTIVES

To investigate whether donkey semen can trigger NET release (NETosis) and if excessive NETosis occurs in response to frozen-thawed semen.

STUDY DESIGN

In vitro experiments.

METHODS

Jenny PMNs were exposed to jackass fresh or frozen-thawed semen, isolated sperm or seminal plasma (SP), over the course of three experiments. NET formation in response to different treatments was assessed through manual quantification of stained slides. A one-way analysis of variance (ANOVA), followed by a post hoc Sidak test, was carried out to determine statistical significance.

RESULTS

NET release occurred in a semen concentration- and incubation-time-dependent manner. Surprisingly, frozen-thawed donkey sperm did not increase NETosis rate in comparison with the control (23 ± 2.5% vs. 31 ± 3.7%; P > .05), whereas fresh semen exposure did (78 ± 5.7% vs. 26 ± 3.2%, P < .01). NETosis increased in the presence of SP, regardless of the presence or absence of sperm, in comparison with the control in both fresh (84 ± 5.2% and 77 ± 5.0% vs. 12 ± 2.7%, respectively; P < .01) and frozen (95 ± 2.2% and 94 ± 2.9% vs. 14 ± 3.8%, respectively; P < .01) samples. Moreover, exposure of PMN to viable and motile sperm, in the absence of SP, did not increase NETosis rates (P > .05).

CONCLUSIONS

Donkey SP, and not sperm-intrinsic factors, is able to trigger NETosis in both time- and semen concentration-dependent manner. The physiological relevance of such response against semen in the donkey remains to be elucidated.

Vaginal neutrophils eliminate sperm by trogocytosis

STUDY QUESTION

What is the vaginal polymorphonuclear (PMN) spermicidal mechanism to reduce the excess of sperm?

SUMMARY ANSWER

We show that PMNs are very efficient at killing sperm by a trogocytosis-dependent spermicidal activity independent of neutrophil extracellular traps (NETs).

WHAT IS KNOWN ALREADY

Trogocytosis has been described as an active membrane exchange between immune cells with a regulatory purpose. Recently, trogocytosis has been reported as a mechanism which PMNs use to kill tumour cells or Trichomonas vaginalis.

STUDY DESIGN, SIZE, DURATION

We used in vivo murine models and human ex vivo sperm and PMNs to investigate the early PMN-sperm response.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We set up a live/dead sperm detection system in the presence of PMNs to investigate in vivo and ex vivo PMN-spermicidal activity by confocal microscopy, flow cytometry and computer-assisted sperm analysis (SCA).

MAIN RESULTS AND THE ROLE OF CHANCE

We revealed that PMNs are highly efficient at killing sperm by way of a NETs-independent, contact-dependent and serine proteases-dependent engulfment mechanism. PMNs 'bite' sperm and quickly reduce sperm motility (within 5 min) and viability (within 20 min) after contact.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This study was conducted using murine models and healthy human blood PMNs; whether it is relevant to human vaginal PMNs or to cases of infertility is unknown.

WIDER IMPLICATIONS OF THE FINDINGS

Vaginal PMNs attack and immobilize excess sperm in the vagina by trogocytosis because sperm are exogenous and may carry pathogens. Furthermore, this mechanism of sperm regulation has low mucosal impact and avoids an exacerbated inflammatory response that could lead to mucosal damage or infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work was partially supported by Ministry of Economy and Competitiveness ISCIII-FIS grants, PI16/00050, and PI19/00078, co-financed by ERDF (FEDER) Funds from the European Commission, 'A way of making Europe' and IiSGM intramural grant II-PI-MRC-2017. M.R. holds a Miguel Servet II contract (CPII14/00009). M.C.L. holds IiSGM intramural contract. There are no competing interests.

Stability of the cytosine methylome during post-testicular sperm maturation in mouse

Beyond the haploid genome, mammalian sperm carry a payload of epigenetic information with the potential to modulate offspring phenotypes. Recent studies show that the small RNA repertoire of sperm is remodeled during post-testicular maturation in the epididymis. Epididymal maturation has also been linked to changes in the sperm methylome, suggesting that the epididymis might play a broader role in shaping the sperm epigenome. Here, we characterize the genome-wide methylation landscape in seven germ cell populations from throughout the male reproductive tract. We find very few changes in the cytosine methylation landscape between testicular germ cell populations and cauda epididymal sperm, demonstrating that the sperm methylome is stable throughout post-testicular maturation. Although our sequencing data suggested that caput epididymal sperm exhibit a highly unusual methylome, follow-up studies revealed that this resulted from contamination of caput sperm by extracellular DNA. Extracellular DNA formed web-like structures that ensnared sperm, and was present only in sperm samples obtained from the caput epididymis and vas deferens of virgin males. Curiously, contaminating extracellular DNA was associated with citrullinated histone H3, potentially resulting from a PAD-driven genome decondensation process. Taken together, our data emphasize the stability of cytosine methylation in mammalian sperm, and identify a surprising, albeit transient, period during which sperm are associated with extracellular DNA.

Semen extender and seminal plasma alter the extent of neutrophil extracellular traps (NET) formation in cattle

During artificial insemination in bovine, the deposition of semen into the uterus results in an immune reaction which is based on polymorphonuclear neutrophils activity, including the formation of neutrophil extracellular traps. The formation of neutrophil extracellular traps as a reaction of neutrophils to spermatozoa was recently described. However, it is not completely clear which components of the semen are responsible for this reaction. The objective of this study was to quantify and compare the formation of neutrophil extracellular traps following in vitro incubation of bovine polymorphonuclear neutrophils with semen and extenders of different origins and conditions. We investigated the interactions between bovine polymorphonuclear neutrophils and different semen extenders, various seminal plasma concentrations from young and old bulls as well as sexed and non-sexed semen and their corresponding extenders. Three different semen extenders from two companies in fresh and frozen-thawed conditions were compared. Fresh semen extenders showed higher neutrophil extracellular traps induction than did frozen-thawed ones. The formation of neutrophil extracellular traps were also dependent on the presence of seminal plasma. We could show that seminal plasma alone, without any sperm cells, induced the reaction and that the addition of at least 1% seminal plasma already resulted in the formation of neutrophil extracellular traps. Furthermore, seminal plasma from young bulls led to significant higher neutrophil extracellular traps induction. No difference between non-sex-sorted and sex-sorted sperm and its extenders was observed. Taken together, different semen extenders as well as the amount and origin of seminal plasma influence neutrophil extracellular traps formation, whereas sex-sorted sperm did not affect the reaction.

Sperm interactions with the female reproductive tract: A key for successful fertilization in mammals

Sperm migration through the female genital tract is not a quiet journey. Uterine contractions quickly operate a drastic selection, leading to a very restrictive number of sperm reaching the top of uterine horns and finally, provided the presence of key molecules on sperm, the oviduct, where fertilization takes place. During hours and sometimes days before fertilization, subpopulations of spermatozoa interact with dynamic and region-specific maternal components, including soluble proteins, extracellular vesicles and epithelial cells lining the lumen of the female tract. Interactions with uterine and oviductal cells play important roles for sperm survival as they modulate the maternal immune response and allow a transient storage before ovulation. The body of work reported here highlights the importance of sperm interactions with proteins originated from both the uterine and oviductal fluids, as well as hormonal signals around the time of ovulation for sperm acquisition of fertilizing competence.

A Higher Abundance of O-Linked Glycans Confers a Selective Advantage to High Fertile Buffalo Spermatozoa for Immune-Evasion From Neutrophils

The glycans on the plasma membrane of cells manifest as the glycocalyx, which serves as an information-rich frontier that is directly in contact with its immediate milieu. The glycoconjugates (GCs) that adorn most of the mammalian cells are also abundant in gametes, especially the spermatozoa where they perform unique reproduction-specific functions e.g., inter-cellular recognition and communication. This study aimed to implicate the sperm glycosylation pattern as one of the factors responsible for low conception rates observed in buffalo bulls. We hypothesized that a differential abundance of glycans exists on the spermatozoa from bulls of contrasting fertilizing abilities endowing them with differential immune evasion abilities. Therefore, we investigated the role of glycan abundance in the phagocytosis and NETosis rates exhibited by female neutrophils (PMNs) upon exposure to such spermatozoa. Our results indicated that the spermatozoa from high fertile (HF) bulls possessed a higher abundance of O-linked glycans e.g., galactosyl (β-1,3)N-acetylgalactosamine and N-linked glycans like [GlcNAc]1-3, N-acetylglucosamine than the low fertile (LF) bull spermatozoa. This differential glycomic endowment appeared to affect the spermiophagy and NETosis rates exhibited by the female neutrophil cells (PMNs). The mean percentage of phagocytizing PMNs was significantly different (P < 0.0001) for HF and LF bulls, 28.44 and 59.59%, respectively. Furthermore, any introduced perturbations in the inherent sperm glycan arrangements promoted phagocytosis by PMNs. For example, after in vitro capacitation the mean phagocytosis rate (MPR) rate in spermatozoa from HF bulls significantly increased to 66.49% (P < 0.01). Likewise, the MPR increased to 70.63% (p < 0.01) after O-glycosidase & α2-3,6,8,9 Neuraminidase A treatment of spermatozoa from HF bulls. Moreover, the percentage of PMNs forming neutrophil extracellular traps (NETs) was significantly higher, 41.47% when exposed to spermatozoa from LF bulls vis-à-vis the spermatozoa from HF bulls, 15.46% (P < 0.0001). This is a pioneer report specifically demonstrating the role of O-linked glycans in the immune responses mounted against spermatozoa. Nevertheless, further studies are warranted to provide the measures to diagnose the sub-fertile phenotype thus preventing the losses incurred by incorrect selection of morphologically normal sperm in the AI/IVF reproduction techniques.

Increase of leucocyte-derived extracellular traps (ETs) in semen samples from human acute epididymitis patients-a pilot study

PURPOSE

To study the effector mechanism against pathogens of polymorphonuclear neutrophils (PMN) and macrophages, called ETosis, involving the release of extracellular traps (ETs) in patients with acute epididymitis. To assess the different ET phenotypes present in semen samples and to identify correlations between ETosis and clinical parameters.

MATERIALS AND METHODS

Samples from patients diagnosed with acute epididymitis were examined and compared with samples from uninfected controls. Biochemical analyses of seminal fluid included determination of peroxidase, α-glucosidase, fructose, and elastase levels. ETosis in semen was determined through presence of citrullinated histones, global histones, and extracellular DNA. Different ETosis phenotypes such as spread ETs, aggregated ETs, and diffuse ETs were identified by co-localisation of extruded DNA with myeloperoxidase and global histones. Anti-CD15⁺ and anti-CD68⁺ antibodies were used to identify different cell lines.

RESULTS

Revealed a high number of ETs compared with the control group. The mean number of CD15⁺PMN and CD68⁺ macrophages was higher in the acute epididymitis group. ETosis increase in ejaculates correlated with clinical parameters such as enhancement of elastase concentrations and diminution of fructose in the semen.

CONCLUSIONS

This work shows for the first time the presence of ETs and their components in semen from patients with acute epididymitis. The presence of infections is an important factor for induction of ETs in semen. Furthermore, the presence of ETosis in ejaculates is suggestive of developing infectious processes and might possibly have a diagnostic value.

Multilevel approach to male fertility by machine learning highlights a hidden link between haematological and spermatogenetic cells

BACKGROUND

Male infertility represents a complex clinical condition requiring an accurate multilevel assessment, in which machine learning technology, combining large data series in non-linear and highly interactive ways, could be innovatively applied.

METHODS

A longitudinal, observational, retrospective, big data study was carried out, applying for the first time the ML in the context of male infertility. A large database including all semen samples collected between 2010 and 2016 was generated, together with blood biochemical examinations, environmental temperature and air pollutants exposure. First, the database was analysed with principal component analysis and multivariable linear regression analyses. Second, classification analyses were performed, in which patients were a priori classified according to semen parameters. Third, machine learning algorithms were applied in a training phase (80% of the entire database) and in a tuning phase (20% of the data set). Finally, conventional statistical analyses were applied considering semen parameters and those other variables extracted during machine learning.

RESULTS

The final database included 4239 patients, aggregating semen analyses, blood and environmental parameters. Classification analyses were able to recognize oligozoospermic, teratozoospermic, asthenozoospermic and patients with altered semen parameters (0.58 accuracy, 0.58 sensitivity and 0.57 specificity). Machine learning algorithms detected three haematological variables, that is lymphocytes number, erythrocyte distribution and mean globular volume, significantly related to semen parameters (0.69 accuracy, 0.78 sensitivity and 0.41 specificity).

CONCLUSION

This is the first machine learning application to male fertility, detecting potential mathematical algorithms able to describe patients' semen characteristics changes. In this setting, a possible hidden link between testicular and haematopoietic tissues was suggested, according to their similar proliferative properties.

FSH for the Treatment of Male Infertility

Follicle-stimulating hormone (FSH) supports spermatogenesis acting via its receptor (FSHR), which activates trophic effects in gonadal Sertoli cells. These pathways are targeted by hormonal drugs used for clinical treatment of infertile men, mainly belonging to sub-groups defined as hypogonadotropic hypogonadism or idiopathic infertility. While, in the first case, fertility may be efficiently restored by specific treatments, such as pulsatile gonadotropin releasing hormone (GnRH) or choriogonadotropin (hCG) alone or in combination with FSH, less is known about the efficacy of FSH in supporting the treatment of male idiopathic infertility. This review focuses on the role of FSH in the clinical approach to male reproduction, addressing the state-of-the-art from the little data available and discussing the pharmacological evidence. New compounds, such as allosteric ligands, dually active, chimeric gonadotropins and immunoglobulins, may represent interesting avenues for future personalized, pharmacological approaches to male infertility.

Antiphospholipid syndrome and infertility

Antiphospholipid syndrome is a systemic autoimmune disease associated with obstetric complications along with vascular events affecting multiple organ systems in patients having positive titers of antiphospholipid antibodies. Eight to 20% of infertility cases have an unknown cause, part of which could be due to antiphospholipid syndrome. Although still debatable, many studies have addressed the relation between reproductive failure and antiphospholipid antibodies through the relation between antiphospholipid antibodies and unexplained infertility as well as the effect of antiphospholipid antibodies on the outcome of in vitro fertilization–embryo transfer. Few studies and cases have associated the presence of antiphospholipid antibodies with male infertility, describing morphofunctional penile abnormalities and testicular infarction. There are not enough data to support the routine practice of testing antiphospholipid antibodies in patients with infertility.

Determination of leucocyte extracellular traps (ETs) in seminal fluid (ex vivo) in infertile patients-A pilot study

Leucocytospermia has been associated with loss of sperm function. Extracellular traps (ETs) of leucocytes are produced during innate immune response. ETs can be activated by spermatozoa in contact with polymorphonuclear (in vitro), inducing sperm entrapment and decrease motility. In this pilot study, we describe the results of ETosis ex vivo, in seminal fluid (SF) smear of infertile patients, associating ETs with leucocytospermia and bacteriospermia. In 21 infertile patients, semen parameters (WHO, 2010), microbiological study, leucocytospermia and presence of ETs in SF were determined. Leucocytes (CD45, CD15 and CD68) were evaluated by immunostaining in SF smears. Indirect immunofluorescence (global histone and H4-citrullinated 3) and scanning electron microscopy (SEM) were used to determine ETs morphology. In 28.6% of patients presented leucocytospermia without bacteriospermia, all of them presented a large number of ETs in the SF smears examined. About 76.6% of the patients without leucocytospermia were positive for ETs. Samples with leucocytospermia have a higher number of ETs and would be related to the amount of leucocytes in the SF. The morphological predominant ETs were diffuse (diffETs) and spread (sprETs). The formation of ETs indicates leucocyte activation in semen, and it was observed that ETosis does not depend exclusively on the presence of bacterial contamination.

Monocyte-derived extracellular trap (MET) formation induces aggregation and affects motility of human spermatozoa in vitro

The presence of bacteria and/or leukocytes can alter semen quality resulting in low sperm quality and infertility. Inflammation or infection increases the numbers of PMN or macrophages/monocytes in male genital tract. Release of extracellular traps (ETs) by leukocytes has been recognized as a novel mechanism of early host innate immunity, in response to invasive pathogens. This is the first work that evaluated the mechanism of triggered ETs in monocytes co-incubated with spermatozoa or bacteria and the effect on sperm function. Selected spermatozoa and human monocytes isolated from peripheral blood were obtained by healthy donors. Two experimental models were developed, one aseptic (non-infectious) incubating spermatozoa and monocytes, and septic models (infectious) incubating spermatozoa with monocytes and uropathogenic Escherichia coli (E. coli). ETs of monocytes (METs) (DNA, global histone and citrullinated histones) were visualized by scanning electron microscopy (SEM) and immunofluorescence analyses. Progressive motility was performed at 0, 10, 30, 60, and 180 min after co-incubation with CASA system. SEM- and immunofluorescence-analyses revealed human spermatozoa alone or in the presence of E. coli as strong inducers METs. In aseptic model, the motility decreased to 65.2 ± 3.5% at 10 min of incubation and 29.3 ± 3.3% at 30 min (p < 0.001). In septic model, motility decreased to 44.5 ± 5.9% (10 min) and 12.7 ± 2.2% (30 min) (p < 0.001). MET-derived small spermatozoa aggregations were observed in both models. METs might physically block spermatozoa and decrease motility after a brief contact. This may impair male fertility, especially in patients with genital tract infections or chronic inflammation. Abbreviations: PMN: polymorphonuclear; ETs: extracellular traps; E. coli: Escherichia coli; METs: ETs of monocytes; SEM: scanning electron microscopy; NE: neutrophil elastase; MPO: myeloperoxidase; MAGI: male accessory gland infection; PBMC: peripheral blood mononuclear cells; RT: room temperature; CFU: colony forming units; CASA: computer-aided sperm analysis; H4Cit3: histone H4 citrullinated 3.

Simultaneous and Positively Correlated NET Formation and Autophagy in Besnoitia besnoiti Tachyzoite-Exposed Bovine Polymorphonuclear Neutrophils

Given that B. besnoiti tachyzoites infect host endothelial cells of vessels in vivo, they become potential targets for professional phagocytes [e.g., polymorphonuclear neutrophils (PMN)] when in search for adequate host cells or in case of host cell lysis. It was recently reported that B. besnoiti-tachyzoites can efficiently be trapped by neutrophil extracellular traps (NETs) released by bovine PMN. So far, the potential role of autophagy in parasite-triggered NET formation is unclear. Thus, we here analyzed autophagosome formation and activation of AMP-activated protein kinase α (AMPKα) in potentially NET-forming innate leukocytes being exposed to B. besnoiti tachyzoites. Blood was collected from healthy adult dairy cows, and bovine PMN were isolated via density gradient centrifugation. Scanning electron microscopy confirmed PMN to undergo NET formation upon contact with B. besnoiti tachyzoites. Nuclear area expansion (NAE) analysis and cell-free and anchored NETs quantification were performed in B. besnoiti-induced NET formation. Interestingly, tachyzoites of B. besnoiti additionally induced LC3B-related autophagosome formation in parallel to NET formation in bovine PMN. Notably, both rapamycin- and wortmannin-treatments failed to influence B. besnoiti-triggered NET formation and autophagosome formation. Also, isolated NETs fail to induce autophagy suggesting independence between both cellular processes. Finally, enhanced phosphorylation of AMP activated kinase α (AMPKα), a key regulator molecule of autophagy, was observed within the first minutes of interaction in tachyzoite-exposed PMN thereby emphasizing that B. besnoiti-triggered NET formation indeed occurs in parallel to autophagy.

Sperm success and immunity

The moment of the fertilization of an egg by a spermatozoon-the point of "sperm success"-is a key milestone in the biology of sexually reproducing species and is a fundamental requirement for offspring production. Fertilization also represents the culmination of a suite of sexually selected processes in both sexes and is commonly used as a landmark to measure reproductive success. Sperm success is heavily dependent upon interactions with other key aspects of male and female biology, with the immune system among the most important. The immune system is vital to maintaining health in both sexes; however, immune reactions can also have antagonistic effects on sperm success. The effects of immunity on sperm success are diverse, and may include trade-offs in the male between investment in the production or protection of sperm, as well as more direct, hostile, immune responses to sperm within the female, and potentially the male, reproductive tract. Here, we review current understanding of where the biology of immunity and sperm meet, and identify the gaps in our knowledge.

The role of neutrophil activation in determining the outcome of pregnancy and modulation by hormones and/or cytokines

Neutrophils are often exclusively considered as a first-line innate immune defence, able to rapidly kill or trap pathogens and causing in case of over-activation tissue damage. In the female reproductive tract, however, the presence and activity of neutrophils seems to be tightly regulated. Major players in orchestrating this regulation are cyclical steroid sex hormones present during the menstrual cycle and pregnancy. This review describes the role of sex hormones in regulating directly or indirectly the functionality of neutrophils, the role of neutrophils during fertilization and pregnancy and in controlling viral, fungal and bacterial infection. This review also discusses the consequence of overt neutrophil activation in pregnancy pathologies.

Pinniped- and Cetacean-Derived ETosis Contributes to Combating Emerging Apicomplexan Parasites (Toxoplasma gondii, Neospora caninum) Circulating in Marine Environments

Leukocytes play a major role in combating infections either by phagocytosis, release of antimicrobial granules, or extracellular trap (ET) formation. ET formation is preceded by a certain leukocyte cell death form, known as ETosis, an evolutionarily conserved mechanism of the innate immune system also observed in marine mammals. Besides several biomolecules and microbial stimuli, marine mammal ETosis is also trigged by various terrestrial protozoa and metazoa, considered nowadays as neozoan parasites, which are circulating in oceans worldwide and causing critical emerging marine diseases. Recent studies demonstrated that pinniped- and cetacean-derived polymorphonuclear neutrophils (PMNs) and monocytes are able to form different phenotypes of ET structures composed of nuclear DNA, histones, and cytoplasmic peptides/proteases against terrestrial apicomplexan parasites, e.g., Toxoplasma gondii and Neospora caninum. Detailed molecular analyses and functional studies proved that marine mammal PMNs and monocytes cast ETs in a similar way as terrestrial mammals, entrapping and immobilizing T. gondii and N. caninum tachyzoites. Pinniped- and cetacean leukocytes induce vital and suicidal ETosis, with highly reliant actions of nicotinamide adenine dinucleotide phosphate oxidase (NOX), generation of reactive oxygen species (ROS), and combined mechanisms of myeloperoxidase (MPO), neutrophil elastase (NE), and DNA citrullination via peptidylarginine deiminase IV (PAD4).This scoping review intends to summarize the knowledge on emerging protozoans in the marine environment and secondly to review limited data about ETosis mechanisms in marine mammalian species.

Estradiol impairs epithelial CXCL1 gradient in the cervix to delay neutrophil transepithelial migration during insemination

Female reproductive mucosa must allow allogenic sperm survival whereas at the same time, avoid pathogen infection. To preserve sperm from neutrophil attack, neutrophils disappear from the vagina during the ovulatory phase (high estradiol); although the mechanisms that regulate neutrophil influx to the vagina during insemination remain controversial. We investigated the sex hormone regulation of the neutrophil migration through the cervix during insemination and revealed that ovulatory estradiol dose fades the CXCL1 epithelial expression in the ectocervix and fornix; hence, retarding neutrophil migration and retaining them in the epithelium. These mechanisms spare sperm from neutrophil attack to preserve reproduction, but might compromise immunity. However, luteal progesterone dose promotes the CXCL1 gradient expression to restore neutrophil migration, to eliminate sperm and prevent sperm associated pathogen dissemination. Surprisingly, these mechanisms are hormone dependent and independent of the insemination. Thus, sex hormones orchestrate tolerance and immunity in the vaginal lumen by regulating neutrophil transepithelial migration in the fornix and ectocervix.

An autoregressive logistic model to predict the reciprocal effects of oviductal fluid components on in vitro spermophagy by neutrophils in cattle

After intercourse/insemination, large numbers of sperm are deposited in the female reproductive tract (FRT), triggering a massive recruitment of neutrophils (PMNs) into the FRT, possibly to eliminate excessive sperm via phagocytosis. Some bovine oviductal fluid components (BOFCs) have been shown to regulate in vitro sperm phagocytosis (spermophagy) by PMNs. The modeling approach-based logistic regression (LR) and autoregressive logistic regression (ALR) can be used to predict the behavior of complex biological systems. We, first, compared the LR and ALR models using in vitro data to find which of them provides a better prediction of in vitro spermophagy in bovine. Then, the best model was used to identify and classify the reciprocal effects of BOFCs in regulating spermophagy. The ALR model was calibrated using an iterative procedure with a dynamical search direction. The superoxide production data were used to illustrate the accuracy in validating logit model-based ALR and LR. The ALR model was more accurate than the LR model. Based on in vitro data, the ALR predicted that the regulation of spermophagy by PMNs in bovine oviduct is more sensitive to alpha-1 acid glycoprotein (AGP), PGE2, bovine serum albumin (BSA), and to the combination of AGP or BSA with other BOFCs.