Involvement of mitochondrial dysfunction in the adverse effect exerted by seminal plasma from men with spinal cord injury on sperm motility

Relationship between male aging and semen quality: a retrospective study on over 2500 men

PURPOSE

We aimed to evaluate whether and to what extent an association exists between male aging and worsening of semen parameters and to determine whether a threshold age can be identified above which the decline in semen quality becomes statistically significant.

METHODS

2612 men (age: 16-56 years) attending an andrology outpatient clinic for semen analysis and clinical evaluation were studied. Semen analyses were performed according to the ongoing WHO-recommended procedures. Total motile count (TMC) and total progressive motile count (TPMC) were calculated by multiplying total sperm number by total motility and progressive motility, respectively.

RESULTS

Significant negative correlations were found between age and total motility (r = - 0.131, p < 0.0001), progressive motility (r = - 0.112, p < 0.0001), TPMC (r = - 0.042, p = 0.037), and normal sperm morphology (r = - 0.053, p = 0.007). All these associations persisted in multivariate regression models adjusted for abstinence time, smoking, history of male accessory gland infections, varicocele and the year in which semen analysis was performed. When comparisons were performed among quartiles of increasing age, the fourth quartile, corresponding to the age group > 40 years, was associated with a significant decrease in total and progressive motility. An earlier decline in the TPMC and percentage of normal forms was also observed.

CONCLUSION

Advancing male age exhibits an independent association with a decrease in the percentage of motile and morphologically normal spermatozoa, with greater evidence from the age of > 40 years. Further studies are warranted to elucidate the mechanisms and clinical reflections of these associations.

Quality of testicular spermatozoa improves with changes in composition of culture medium

BACKGROUND

Spermatozoa retrieved from the testis and epididymis are deprived of the beneficial effects of seminal fluid. Thus applying an artificial medium with normal seminal fluid characteristics, known as artificial seminal fluid (ASF), may provide an appropriate condition for improving some sperm parameters in azoospermia. The objective was to investigate the impact of in vitro exposure of testicular and epididymal spermatozoa to ASF on sperm quality. The study was conducted on testicular (n = 20) and epididymal (n = 20) sperm specimens obtained from azoospermic men. Each sample was divided into two equal parts: Part I) for processing and incubation with Ham's F10 medium; Part II) for processing and incubation with ASF.

RESULTS

After 2 h incubation, testicular sperm motility was significantly higher in ASF than in Ham's F10 medium. In comparison to 0 h, mitochondrial membrane potential levels of testicular spermatozoa were significantly higher after 2 h and 24 h in ASF and after 24 h in Ham's F10 medium. Furthermore, the data indicated significantly lower rates of epididymal spermatozoa with high MMP in both media after 24 h. There were no significant differences in the DNA fragmentation index of testicular and epididymal spermatozoa between ASF and Ham's F10 medium at different time points.

CONCLUSION

The results demonstrated that in vitro incubation of testicular spermatozoa improved their motility more effectively than Ham's F10 medium in the short term (2 h), but had no effect on epididymal spermatozoa. Since the physiology of testicular spermatozoa is different from that of ejaculated spermatozoa, it seems that a special environment should be designed and used for each of them.

The Female Reproductive Tract Microbiota: Friends and Foe

We do not seem to be the only owner of our body; it houses a large population of microorganisms. Through countless years of coevolution, microbes and hosts have developed complex relationships. In the past few years, the impact of microbial communities on their host has received significant attention. Advanced molecular sequencing techniques have revealed a remarkable diversity of the organ-specific microbiota populations, including in the reproductive tract. Currently, the goal of researchers has shifted to generate and perceive the molecular data of those hidden travelers of our body and harness them for the betterment of human health. Recently, microbial communities of the lower and upper reproductive tract and their correlation with the implication in reproductive health and disease have been extensively studied. Many intrinsic and extrinsic factors influences the female reproductive tract microbiota (FRTM) that directly affects the reproductive health. It is now believed that FRTM dominated by Lactobacilli may play an essential role in obstetric health beyond the woman's intimate comfort and well-being. Women with altered microbiota may face numerous health-related issues. Altered microbiota can be manipulated and restored to their original shape to re-establish normal reproductive health. The aim of the present review is to summarize the FRTM functional aspects that influence reproductive health.

Sperm Mitochondria, the Driving Force Behind Human Spermatozoa Activities: Its Functions and Dysfunctions - A Narrative Review

Male infertility is a major issue, and numerous factors contribute to it. One of the important organelles involved in the functioning of human spermatozoa is mitochondria. There are 50-75 mitochondria helically arranged in mid-piece bearing one mitochondrial DNA each. Sperm mitochondria play a crucial role in sperm functions, including the energy production required for sperm motility and the production of reactive oxygen species, which in the physiological range helps in sperm maturation, capacitation, and acrosome reaction. It also plays a role in calcium signaling cascades, intrinsic apoptosis, and sperm hyperactivation. Any structural or functional dysfunction of sperm mitochondria results in increased production of reactive oxygen species and, a state of oxidative stress, decreased energy production, all leading to sperm DNA damage, impaired sperm motility and semen parameters, and reduced male fertility. Furthermore, human sperm mitochondrial DNA mutations can result in impaired sperm motility and parameters leading to male infertility. Numerous types of point mutations, deletions, and missense mutations have been identified in mtDNA that are linked with male infertility. Methods: Recent literature was searched from English language peer-reviewed journals from databases including PubMed, Scopus, EMBASE, Scholar, and Web of Science till September 2021. Search terms used were "Sperm mitochondria and male fertility", "Bioenergetics of sperm", "Sperm mitochondria and reactive oxygen species", "Sperm mitochondrial mutations and infertility". Conclusion: Sperm mitochondria is an important organelle involved in various functions of human spermatozoa and sperm mitochondrial DNA has emerged as one of the potent biomarkers of sperm quality and male fertility.

Reduction of SLC7A11 and GPX4 Contributing to Ferroptosis in Sperm from Asthenozoospermia Individuals

Ferroptosis is a newly defined form of regulated cell death, which is involved in various pathophysiological conditions. However, the role of ferroptosis in male infertility remains unclear. In this study, 42 asthenozoospermic and 45 normozoospermic individuals participated. To investigate the ferroptosis level in the two groups, the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and iron were measured, and mitochondrial membrane potential (MMP) was detected as an indicator of mitochondrial injuries. Compared with the normozoospermic group, ROS (p < 0.05), MDA (p < 0.001), and iron (p < 0.001) of the asthenozoospermic group were significantly increased. However, the asthenozoospermia group had a decreased MMP level (p < 0.05). In addition, the expression levels of GSH-dependent peroxidase 4 (GPX4) (p < 0.001) and solute carrier family 7 member 11 (SLC7A11) (p < 0.05) were also reduced in asthenozoospermic individuals. In asthenozoospermic samples, a significantly high positive correlation was observed between GPX4 mRNA levels and progressive motility (r = 0.397, p = 0.009) and total motility (r = 0.389, p = 0.011), while a negative correlation was observed between GPX4 and iron concentration (r =  - 0.276, p = 0.077). The function of ferroptosis in asthenozoospermic males has never been studied before. In our study, we concluded that GPX4 and SLC7A11 expression levels in asthenozoospermia patients were related to increased ferroptosis and impaired sperm function, revealing novel molecular insights into the complex systems involved in male infertility.

Mitochondria-Targeted Compounds to Assess and Improve Human Sperm Function

Significance: Currently 10%-15% of couples in reproductive age face infertility issues. More importantly, male factor contributes to 50% of these cases (either alone or in combination with female causes). Among various reasons, impaired sperm function is the main cause for male infertility. Furthermore, mitochondrial dysfunction and oxidative stress due to increased reactive oxygen species (ROS) production, particularly of mitochondrial origin, are believed to be the main contributors. Recent Advances: Mitochondrial dysfunction, particularly due to increased ROS production, has often been linked to impaired sperm function/quality. For decades, different methods and approaches have been developed to assess mitochondrial features that might correlate with sperm functionality. This connection is now completely accepted, with mitochondrial functionality assessment used more commonly as a readout of sperm functionality. More recently, mitochondria-targeted compounds are on the frontline for both assessment and therapeutic approaches. Critical Issues: In this review, we summarize the current methods for assessing key mitochondrial parameters known to reflect sperm quality as well as therapeutic strategies using mitochondria-targeted antioxidants aiming to improve sperm function in various situations, particularly after sperm cryopreservation. Future Directions: Although more systematic research is needed, mitochondria-targeted compounds definitely represent a promising tool to assess as well as to protect and improve sperm function. Antioxid. Redox Signal. 37, 451-480.

Effects of bisphenol S and bisphenol F on human spermatozoa: An in vitro study

Bisphenol A (BPA), the main chemical monomer of epoxy resins and polycarbonate plastics, has generated concerns about its endocrine disruptor properties, along with the reported possible links with several human health disorders. Accordingly, some restrictions on its use have been recommended. Bisphenol S (BPS) and bisphenol F (BPF) are the main replacements to BPA, with which they share homologies in chemical structure. However, to date, little is known about their possible adverse effects for human reproduction. As the in vitro exposure of human spermatozoa to BPA induces oxidative/pro-apoptotic effects, the aim of the present study was to verify whether BPS and BPF could represent safer compounds for human sperm functions. The exposure of motile sperm suspensions to scalar concentrations of BPS or BPF for 4 h did not significantly reduce sperm motility (as assessed by computer-aided semen analysis) and viability. At flow cytometry, no changes in mitochondrial membrane potential, or mitochondrial generation of reactive oxygen species were detected by using the JC-1 and MitoSOX red probes, respectively. Interestingly, it nor even the combination of both BPS and BPF at the highest concentrations impaired sperm mitochondrial functions. In conclusion, BPS and BPF seem to be safer alternatives to BPA for sperm biology, as they do not affect mitochondrial functions, sperm motility and viability. These findings could help regulatory agencies to identify more secure chemicals to replace BPA in industrial production of plastics.

Pathophysiology of Mitochondrial Dysfunction in Human Spermatozoa: Focus on Energetic Metabolism, Oxidative Stress and Apoptosis

The dogma of mitochondria as the major source of energy in supporting sperm motility should be critically reconsidered in the light of several experimental data pointing to a major role of glycolysis in mammalian spermatozoa. In this light, the reported positive correlation between the mitochondrial membrane potential (ΔΨm) and motility of ejaculated spermatozoa cannot be explained convincingly by an impaired mitochondrial ATP generation only. Evidence has been produced suggesting that, in human sperm, dysfunctional mitochondria represent the main site of generation of reactive oxygen species (ROS). Furthermore, in these organelles, a complex bidirectional relationship could exist between ROS generation and apoptosis-like events that synergize with oxidative stress in impairing sperm biological integrity and functions. Despite the activity of enzymatic and non-enzymatic antioxidant factors, human spermatozoa are particularly vulnerable to oxidative stress, which plays a major role in male factor infertility. The purpose of this article is to provide an overview of metabolic, oxidative and apoptosis-like inter-linkages of mitochondrial dysfunction and their reflections on human sperm biology.

The incidence and etiology of sperm DNA fragmentation in the ejaculates of males with spinal cord injuries

STUDY DESIGN

Retrospective descriptive study.

OBJECTIVES

To determine the incidence and probable etiology of sperm DNA fragmentation (SDF) in a sample of males with spinal cord injury (SCI).

SETTING

Hospital in Toledo, Spain; University-based Genetics laboratory in Madrid, Spain.

METHODS

Semen collected by vibro-stimulation from 27 males with various levels of spinal cord injury. Classical semen parameters, SDF, leukocytospermia and pro-oxidant capacity were assessed and compared with a cohort of normozoospermic fertile donors (n = 10).

RESULTS

Males with SCI presented with lower semen quality compared with normozoospermic donors with respect to progressive motility (p = 0.0002), SDF (p < 0.00005), pro-oxidant capacity (p = 0.0191) and leukocytospermia (p < 0.00005). Although there was no significant correlation between semen quality and time since the lesion occurred, the period of abstinence appeared to be positively correlated with SDF (r = 0.486; p = 0.041). When the semen parameters of males with SCI were categorized based on those with cervical and thoracic lesions, sperm concentration was higher for those with cervical damage (p = 0.0257). Males with complete lesions (AIS A) had ejaculates that were lower in progressive motility (p = 0.0040) than those with incomplete injuries (AIS B-D).

CONCLUSIONS

Ejaculates of males with SCI have excessively elevated SDF when compared with normozoospermic donors, which is likely to be associated with coincident high levels of leucocytospermia and pro-oxidant capacity. We propose that these phenomena are caused by the accumulation and degeneration of spermatozoa in the cauda epididymidis.

Bio-Functional Sperm Parameters: Does Age Matter?

The evaluation of biofunctional sperm parameters can explain some cases of idiopathic male infertility. Among these, sperm DNA fragmentation (fDNA) is the most studied biofunctional sperm parameter. Mitochondrial membrane potential (MMP) correlates positively with sperm motility, the evaluation of sperm apoptosis by flow cytometry allows us to identify a population of spermatozoa not recognizable at the optical microscopy and finally, lipid peroxidation (LP) and mitochondrial superoxide levels measurements are rational oxidative stress indices. Male age seems to affect sperm concentration and sperm fDNA. For these reasons, this study was undertaken to evaluate the correlation, if any, between male age and biofunctional sperm parameters evaluating their possible impact on fDNA. To accomplish this, MMP, degree of chromatin compactness, sperm apoptosis/vitality, fDNA, LP, and mitochondrial superoxide levels were evaluated by flow cytometry in a cohort of 874 men. A significant negative correlation was found between age and the percentage of alive spermatozoa (r = -0.75, p < 0.05). The percentage of spermatozoa with low MMP (L-MMP) correlated positively with the percentage of spermatozoa with abnormal chromatin compactness (r = 0.24, p < 0.05). Spermatozoa with abnormal chromatin compactness and L-MMP correlated negatively with the percentage of alive spermatozoa (r = 0.83, p < 0.05) and positively with spermatozoa with PS externalization (r = 0.13, p < 0.01). The percentage of alive spermatozoa correlated negatively with both the percentage of spermatozoa with PS externalization (r = 0.24, p < 0.01) and of the spermatozoa with fDNA (r = 0.10, p < 0.05). Spermatozoa with PS externalization correlated positively with the percentage of spermatozoa with fDNA (r = 0.09, p < 0.05). Spermatozoa with LP correlated positively with the percentage of spermatozoa with increased mitochondrial superoxide (r = 0.11, p < 0.01) In conclusion, these findings in a large number of men suggest that age, mitochondrial damage, and alteration of chromatin compactness could activate the apoptotic cascade which could result in an increased fDNA rate.

Environment and Male Fertility: Effects of Benzo-α-Pyrene and Resveratrol on Human Sperm Function In Vitro

Lifestyle, cigarette smoking and environmental pollution have a negative impact on male fertility. Therefore, the aim of this study was to evaluate the in-vitro effects of benzo-α-pyrene (BaP) and aryl hydrocarbon receptor (AHR) agonists on motility and bio-functional sperm parameters. We further assessed whether resveratrol (RES), an AHR antagonist and antioxidant molecule, had any protective effect. To accomplish this, 30 normozoospermic, healthy, non-smoker men not exposed to BaP were enrolled. Spermatozoa of 15 men were incubated with increasing concentrations of BaP to evaluate its effect and to establish its dose response. Then, spermatozoa of the 15 other men were incubated with BaP (15 µM/mL), chosen according to the dose-response and/or RES to evaluate its antagonistic effects. The effects of both substances were evaluated after 3 h of incubation on total and progressive sperm motility and on the following bio-functional sperm parameters evaluated by flow cytometry: Degree of chromatin compactness, viability, phosphatidylserine externalization (PS), late apoptosis, mitochondrial membrane potential (MMP), DNA fragmentation, degree of lipoperoxidation (LP), and concentrations of mitochondrial superoxide anion. Benzo-α-pyrene decreased total and progressive sperm motility, impaired chromatin compactness, and increased sperm lipoperoxidation and mitochondrial superoxide anion levels. All these effects were statistically significant at the lowest concentration tested (15 µM/mL) and they were confirmed at the concentration of 45 µM/mL. In turn, RES was able to counteract the detrimental effects of BaP on sperm motility, abnormal chromatin compactness, lipid peroxidation, and mitochondrial superoxide. This study showed that BaP alters sperm motility and bio-functional sperm parameters and that RES exerts a protective effect on BaP-induced sperm damage.

Testosterone Reduces Spinal Cord Injury-Induced Effects on Male Reproduction by Preventing CADM1 Defect

Objective

This study evaluated the effects of exogenous testosterone molecule-1 (CADM1) pathological defect during early and chronic periods of spinal cord injury (SCI).

Materials and Methods

In this experimental study, testosterone was administered immediately or after one week of SCI induction. Along with quantification of CADM1 gene expression and its immunoreactivity, we evaluated sperm parameters and serum testosterone level post-SCI.

Results

Different grades of abnormalities in sperm parameters and testis architecture were observed along with significant reductions in the level of CADM1 expression and its immunoreactivity in the seminiferous tubules of both acute and chronic SCI groups. Exogenous testosterone, by compensating the serum testosterone level. reduced the percentage of apoptotic and both short head and abnormal sperm froms in the caudal epididymis. Importantly, the beneficial effects of immediate administration of testosterone were prominent. Increases in the level of CADM1 transcription and its immunoreactivity in the testis of SCI mice treated with testosterone were accompanied by improvement of sperm motility as well as testicular Johnsen’s and Miller’s criteria.

Conclusion

Since immediate testosterone treatment improved the immunoreactivity and transcription level of CADM1, the observed beneficial effect of exogenouse testosterone can be attributed to its effect on CADM1 dynamics.

Diabetes Mellitus and Infertility: Different Pathophysiological Effects in Type 1 and Type 2 on Sperm Function

Although the prevalence of sub-infertility in diabetic patients in childbearing age is known, the mechanisms by which diabetes mellitus (DM) causes male infertility are not completely explained. This detrimental effect is achieved with a variety of mechanisms that include pre-testicular, testicular, and post-testicular pathogenetic moments and can be different in type 1 diabetes mellitus (DM1) and type 2 diabetes mellitus (DM2) patients because of type of diabetes, duration of disease, and glycemic metabolic compensation. Aim of this study was to evaluate whether diabetic disease can be considered a risk factor for infertility considering the etiopathogenetic differences between DM1 and DM2 on sperm function. We enrolled 38 DM1 patients and 55 DM2 patients with idiopathic infertility history >12 months, and 100 healthy fertile subjects. The following outcomes were evaluated in optical microscopy and flow cytometry: sperm function (by conventional and biofunctional sperm parameters) and signs of urogenital infection/inflammation (by sperm leukocyte concentrations and indices of oxidative stress). Moreover, an andrological evaluation (by didymo-epididymal ultrasound evaluation, serum total testosterone, LH, and FSH measurements) was performed in DM1 and DM2 patients compared to controls. Diabetic patients showed a higher risk of becoming infertile and the pathophysiological mechanisms of damage were different in DM1 and DM2. Conventional sperm parameters of diabetic patients are worse than controls (p < 0.05). The DM2 caused an inflammatory condition with increased oxidative stress resulting in decreased sperm vitality and increased sperm DNA fragmentation. DM1 altered epididymal voiding causing low ejaculate volume and mitochondrial damage resulting in decreased sperm motility. These findings and evidences support the contention that DM could be regarded as cause of male infertility suggesting that the prevention of diabetic disease in DM2 and the follow-up of seminal parameters in DM1 could prevent fertility decline in these categories of patients.

Reactive oxygen species mediate Terbufos-induced apoptosis in mouse testicular cell lines via the modulation of cell cycle and pro-apoptotic proteins

Terbufos (S-t-butylthiomethyl-O,O-diethyl phosphorodithioate) is a highly toxic organophosphate which is extensively used as an insecticide and nematicide. Chronic exposure to terbufos causes neuronal injury and predisposes to neurodegenerative diseases. Accumulating evidence has shown that the exposure to terbufos, as an occupational risk factor, may also cause reproductive disorders. However, the exact mechanisms of reproductive toxicity remain unclear. The present study aimed to investigate the toxic effect of terbufos on testicular cells and to explore the mechanism of toxicity on a cellular level. The cytotoxic effects of terbufos on mouse immortalized spermatogonia (GC-1), spermatocytes (GC-2), Leydig (TM3), and Sertoli (TM4) cell lines were assessed by MTT assays, caspase activation, flow cytometry, TUNEL assay, Western blot, and cell cycle analysis. The exposure to different concentrations of terbufos ranging from 50 to 800 μM for 6 h caused significant death in all the used testicular cell lines. Terbufos increased reactive oxygen species (ROS) production, reduced mitochondrial membrane potential, and initiated apoptosis, which was confirmed by a dose-dependent increase in the number of TUNEL-positive apoptotic cells. Blocking ROS production by N-acetyl cysteine (NAC) protected GC-1 cells from terbufos-induced cell death. The results demonstrated that terbufos induces ROS, apoptosis, and DNA damage in testicular cell lines and it should be considered potentially hazardous to testis. Together, this study provided potential molecular mechanisms of terbufos-induced toxicity in testicular cells and suggests a possible protective measure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1888-1898, 2016.

Hexavalent chromium affects sperm motility by influencing protein tyrosine phosphorylation in the midpiece of boar spermatozoa

Hexavalent chromium reportedly induces reproductive toxicity and further inhibits male fertility in mammals. In this study, we investigated the molecular mechanism by which hexavalent chromium affects motility signaling in boar spermatozoa in vitro. The results indicated that Cr(VI) decreased sperm motility, protein phosphorylation, mitochondrial membrane potential (ΔΨm) and metabolic enzyme activity starting at 4μmol/mL following incubation for 1.5h. Notably, all parameters were potently inhibited by 10μmol/mL Cr, while supplementation with the dibutyryl-cAMP (dbcAMP) and the 3-isobutyl-1-methylxanthine (IBMX) prevented the inhibition of protein phosphorylation. Interestingly, high concentrations of Cr (>10μmol/mL) increased the tyrosine phosphorylation of some high-molecular-weight proteins in the principle piece but decreased that in the middle piece associated with an extreme reduction of sperm motility. These results suggest that chromium affects boar sperm motility by impairing tyrosine phosphorylation in the midpiece of sperm by blocking the cAMP/PKA pathway in boar sperm in vitro.

The mitochondrial division inhibitor mdivi-1 attenuates spinal cord ischemia-reperfusion injury both in vitro and in vivo: Involvement of BK channels

Mitochondrial division inhibitor (mdivi-1), a selective inhibitor of a mitochondrial fission protein dynamin-related protein 1 (Drp1), has been shown to exert protective effects in heart and cerebral ischemia-reperfusion models. The present study was designed to investigate the beneficial effects of mdivi-1 against spinal cord ischemia-reperfusion (SCIR) injury and its associated mechanisms. SCIR injury was induced by glutamate treatment in cultured spinal cord neurons and by descending thoracic aorta occlusion for 20 min in rats. We found that mdivi-1 (10 μM) significantly attenuated glutamate induced neuronal injury and apoptosis in spinal cord neurons. This neuroprotective effect was accompanied by decreased expression of oxidative stress markers, inhibited mitochondrial dysfunction and preserved activities of antioxidant enzymes. In addition, mdivi-1 significantly increased the expression of the large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels, and blocking BK channels by paxilline partly ablated mdivi-1 induced protection. The in vivo experiments showed that mdivi-1 treatment (1 mg/kg) overtly mitigated SCIR injury induced spinal cord edema and neurological dysfunction with no organ-related toxicity in rats. Moreover, mdivi-1 increased the expression of BK channels in spinal cord tissues, and paxilline pretreatment nullified mdivi-1 induced protection after SCIR injury in rats. Thus, mdivi-1 may be an effective therapeutic agent for SCIR injury via activation of BK channels as well as reduction of oxidative stress, mitochondrial dysfunction and neuronal apoptosis. This article is part of a Special Issue entitled SI: Spinal cord injury.

Neutralization of ASC improves sperm motility in men with spinal cord injury

STUDY QUESTION

Does neutralization of apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) improve sperm motility in men with spinal cord injury (SCI)?

SUMMARY ANSWER

Neutralization of ASC improves sperm motility in men with SCI.

WHAT IS KNOWN ALREADY

Semen of men with SCI contains normal sperm concentrations but abnormally low sperm motility. Inflammatory cytokines, activated via the inflammasome complex, are contributory. A key component of the inflammasome is ASC.

STUDY DESIGN, SIZE, DURATION

This prospective study included semen samples collected from 32 men with SCI.

PARTICIPANTS/MATERIALS, SETTING, METHODS

At a major university medical center, untreated semen was compared with semen treated with anti-ASC polyclonal antibody. Semen treated with IgG was used as a control.

MAIN RESULTS AND THE ROLE OF CHANCE

Addition of anti-ASC polyclonal antibody to semen significantly increased mean sperm motility from 11.5% (95% CI, 6.3-16.7) to 18.3% (95% CI, 11.8-24.8). Improvements were most pronounced in the subgroup whose starting motility ranged between 6 and 40%. In this subgroup, the mean sperm motility improved from 13.3% (95% CI, 9.3-17.3) to 23.9% (95% CI, 14.7-23.0). Sperm motility did not improve after treatment with IgG.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by the small sample size as this is a rare population.

WIDER IMPLICATIONS OF THE FINDINGS

Blockade of the inflammasome via treatment with anti-ASC improved sperm motility in men with SCI. In doing so, this treatment significantly increased their total motile sperm count. This is the first study to demonstrate that interference with the inflammasome improves sperm motility in men with SCI. This treatment has potential as a therapeutic intervention.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by the Craig H. Neilsen Foundation, Grant # 224598, the University of Miami Miller School of Medicine and the Miami Project to Cure Paralysis, Miami, FL, USA. R.W.K. and J.P.d.R.V. hold a patent for the treatment of inflammation after central nervous system injury using antibodies against inflammasome proteins. The other authors have no conflicts of interest to declare.

Soluble products of Escherichia coli induce mitochondrial dysfunction-related sperm membrane lipid peroxidation which is prevented by lactobacilli

Unidentified soluble factors secreted by E. coli, a frequently isolated microorganism in genitourinary infections, have been reported to inhibit mitochondrial membrane potential (ΔΨm), motility and vitality of human spermatozoa. Here we explore the mechanisms involved in the adverse impact of E. coli on sperm motility, focusing mainly on sperm mitochondrial function and possible membrane damage induced by mitochondrial-generated reactive oxygen species (ROS). Furthermore, as lactobacilli, which dominate the vaginal ecosystem of healthy women, have been shown to exert anti-oxidant protective effects on spermatozoa, we also evaluated whether soluble products from these microorganisms could protect spermatozoa against the effects of E. coli. We assessed motility (by computer-aided semen analysis), ΔΨm (with JC-1 dye by flow cytometry), mitochondrial ROS generation (with MitoSOX red dye by flow cytometry) and membrane lipid-peroxidation (with the fluorophore BODIPY C₁₁ by flow cytometry) of sperm suspensions exposed to E. coli in the presence and in the absence of a combination of 3 selected strains of lactobacilli (L. brevis, L. salivarius, L. plantarum). A Transwell system was used to avoid direct contact between spermatozoa and microorganisms. Soluble products of E. coli induced ΔΨm loss, mitochondrial generation of ROS and membrane lipid-peroxidation, resulting in motility loss. Soluble factors of lactobacilli prevented membrane lipid-peroxidation of E. coli-exposed spermatozoa, thus preserving their motility. In conclusion, sperm motility loss by soluble products of E. coli reflects a mitochondrial dysfunction-related membrane lipid-peroxidation. Lactobacilli could protect spermatozoa in the presence of vaginal disorders, by preventing ROS-induced membrane damage.