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

Insight toward inflammasome complex contribution to male infertility

During the last decades, a wide range of factors involved in the physiopathology of male infertility disease have been discussed. The inflammation role in some of the main infertility-related diseases has been studied, such as varicocele, spinal cord injury and obesity. Inflammation is the main response of the immune system to infection or cell damage, leading to intense inflammatory cytokine release during the loss of homeostasis. One of the first steps toward pro-inflammatory cytokines release is the recognition of dangerous signals by the immune cells, including pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). These molecules can activate an important multiprotein complex, called inflammasome. Although these complexes have been studied during the last decades, their participation in male infertility has gained attention recently. Considering the inflammasome complex's high potential to be targeted for drug therapy, this review tries to shed light on current literature. Therefore, in the current review paper, we aimed to discuss the inflammasome complex activation, involvement in different male infertility conditions, and localization in the male reproductive tract.

Rescuing fertility during COVID-19 infection: exploring potential pharmacological and natural therapeutic approaches for comorbidity, by focusing on NLRP3 inflammasome mechanism

The respiratory system was primarily considered the only organ affected by Coronavirus disease 2019 (COVID-19). As the pandemic continues, there is an increasing concern from the scientific community about the future effects of the virus on male and female reproductive organs, infertility, and, most significantly, its impact on the future generation. The general presumption is that if the primary clinical symptoms of COVID-19 are not controlled, we will face several challenges, including compromised infertility, infection-exposed cryopreserved germ cells or embryos, and health complications in future generations, likely connected to the COVID-19 infections of parents and ancestors. In this review article, we dedicatedly studied severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) virology, its receptors, and the effect of the virus to induce the activation of inflammasome as the main arm of the innate immune response. Among inflammasomes, nucleotide oligomerization domain-like receptor protein, pyrin domain containing 3 (NLRP3) inflammasome pathway activation is partly responsible for the inflicted damages in both COVID-19 infection and some reproductive disorders, so the main focus of the discussion is on NLRP3 inflammasome in the pathogenesis of COVID-19 infection alongside in the reproductive biology. In addition, the potential effects of the virus on male and female gonad functions were discussed, and we further explored the potential natural and pharmacological therapeutic approaches for comorbidity via NLRP3 inflammasome neutralization to develop a hypothesis for averting the long-term repercussions of COVID-19. Since activation of the NLRP3 inflammasome pathway contributes to the damage caused by COVID-19 infection and some reproductive disorders, NLRP3 inflammasome inhibitors have a great potential to be considered candidates for alleviating the pathological effects of the COVID-19 infection on the germ cells and reproductive tissues. This would impede the subsequent massive wave of infertility that may threaten the patients.

The NLRP3 inflammasome: molecular activation and regulation in spermatogenesis and male infertility; a systematic review

Background

Infertility related to varicocele, infections, metabolic dysfunctions, oxidative stress and environmental toxicants is also associated with inflammatory processes that ultimately lead to the activation of the inflammasome pathway (IP). IP is classically activated by DAMPs, MAMPs or LAMPs, which stand for Damage-, Microbe- or Lifestyle-Associated Molecular Patterns, respectively. The most important player in IP activation is the NLRP3 (NOD[Nuclear oligomerization domain]-, LRR[Leucine rich repeat]- and pyrin domain-containing protein 3) which functions as an intracellular sensor of D/M/L-AMPs resulting in activation of caspase-1, promotion of apoptosis, pyroptosis and generation of inflammatory cytokines. This review addresses the question of whether IP activation might be associated with male infertility situations.

Results & conclusions

We conducted a systematic review of articles published in the Google Scholar, and PubMed databases through October 2021. It turns out that inflammasome activation and its consequences including cytokine storms, apoptosis and pyroptosis could be associated with the reduced sperm count as well as the structural and functional sperm defects recorded in several situations associated with male infertility suggesting that anti-inflammatory therapeutic strategies could be possibly considered to restore male fertility in future research.

Pyroptosis-Induced Inflammation and Tissue Damage

Programmed cell deaths are pathways involving cells playing an active role in their own destruction. Depending on the signaling system of the process, programmed cell death can be divided into two categories, pro-inflammatory and non-inflammatory. Pyroptosis is a pro-inflammatory form of programmed cell death. Upon cell death, a plethora of cytokines are released and trigger a cascade of responses from the neighboring cells. The pyroptosis process is a double-edged sword, could be both beneficial and detrimental in various inflammatory disorders and disease conditions. A physiological outcome of these responses is tissue damage, and sometimes death of the host. In this review, we focus on the inflammatory response triggered by pyroptosis, and resulting tissue damage in selected organs.

Proteomic insight of seminal plasma in spinal cord injured men submitted to oral probenecid treatment for improved motility

OBJECTIVE

To observe the seminal plasma proteomic composition in men with spinal cord injury orally treated with probenecid, in order to observe pathways associated with increased sperm motility.

STUDY DESIGN

Prospective study.

SETTING

Miami Project to Cure Paralysis - University of Miami/Miller School of Medicine.

PARTICIPANTS

Nine men with spinal cord injury, who agreed to participate in the study.

INTERVENTION

Oral treatment with probenecid - 500 mg per day for one week, then 500 mg twice daily [1000 mg total] per day for three weeks.

OUTCOME MEASURES

Semen analysis as per WHO 2010 guidelines, and seminal plasma proteomics analysis by LC-MS/MS.

RESULTS

In total, 783 proteins were identified, of which, 17 were decreased, while 6 were increased after treatment. The results suggest a new pathway that could be treated by the decrease of biglycan after probenecid treatment.

CONCLUSION

Oral treatment with probenecid is able to alter the seminal plasma proteome, in pathways that explain decreased innate immune response.

NLRP3 inflammasome: A joint, potential therapeutic target in management of COVID-19 and fertility problems

To overcome COVID-19 long-term consequences, one possible approach is to control inflammasomes activation, because SARS-CoV-2 can induce humoral and cellular immune responses. In this opinion article we hypothesized that if it is proven with convincing and unmistakable evidence that firstly, SARS-CoV-2 can enter cells and damage them through its common receptors in the reproductive tissues, and secondly, inflammasome pathway activation is responsible for the damages caused, then the inflammasome inhibitors might be considered as suitable candidates in preventing the pathological effects on the germ cells and reproductive tissues and subsequent fertility.

Involvement of Asc and Nlrp3 inflammasomes in the testes following spinal cord injury

OBJECTIVE

The exact mechanism, by which spinal cord injury (SCI) leads to a male subfertility is not well-known. Present study was conducted to determine the mechanisms that lead to the elevated end-product cytokines and inflammasomes in the testes of an SCI rat model. Moreover, we evaluated the inflammasome components following SCI in testis over a defined time periods.

METHODS

Weight drop technique was used to induce SCI at the level of the T10 vertebra in male Wistar rats. The animals were sacrificed at specific time intervals (3, 7, 14, 21, and 28 day's post-SCI). mRNA levels of inflammasomes and cytokines were measured by real-time PCR, germ cells apoptosis was evaluated by TUNEL staining, and the epithelium of seminiferous tubules by Miller's and Johnsen's scores.

RESULTS

The results showed activation of Nlrp3 in the testes of SCI animals at different time points. Expression of Nlrp3 and IL-1β sharply increased 14 days after the SCI. Upregulation of IL-1β and IL-18 at days 14 and 21 post-SCI might disintegrate the epithelium of seminiferous tubules at day 14 and induce germ cells apoptosis, increase abnormal sperm cells, and attenuate motility and viability at 21 days post-SCI.

CONCLUSION

This study provided further evidence of innate immunity activation in testes that could lead to more disruption of spermatogenesis in SCI patients at specific times.

Seminal inflammasome activity in the adult varicocele

Varicocele has been hypothesized to lead to seminal inflammation, which in turn interferes with sperm function. Thus, the aim of this study was to investigate the role of inflammatory cytokines in the pathogenesis of decreased semen quality observed in adult men with varicocele, and to determine if varicocelectomy corrects these potential alterations. A prospective study was carried out including fifteen control men without varicocele and with normal semen quality and 15 men with varicocele with surgical indication. Men with varicocele grades II or III underwent microsurgical subinguinal varicocelectomy. Controls collected one semen sample and men with varicocele collected one before and one 6 months after the surgery. Semen analysis, sperm function, and seminal lipid peroxidation levels were assessed. Seminal plasma inflammasome activity was evaluated by ELISA assays for IL-1β, IL-18 and caspase-1 and by Western blotting for ASC (apoptosis-associated speck-like protein). Groups were compared by an unpaired Student's T test. Varicocelectomy samples were compared using a paired Student's T test (α = 5%). Men with varicocele had decreased semen quality, and increased seminal IL-1β levels, when compared to control men. Varicocelectomy decreased levels of caspase-1, IL-18, and IL1β. Thus, varicocelectomy improves sperm morphology and decreases seminal plasma inflammatory activity, after a six-month post-operative period.

The Inflammasome in Reproductive Biology: A Promising Target for Novel Therapies

The inflammasome is a key regulator of innate immunity involved in the inflammatory response to infections as well as disease through the activation of caspase-1 and the processing of the inflammatory cytokines interleukin (IL)-1β and IL-18. Even though the inflammasome was first described in the context of infections, most research in recent years has focused on targeting the inflammasome as a therapeutic option in sterile inflammatory events. Recent evidence indicates a clear involvement of the inflammasome in Reproductive Biology such as infertility and preeclampsia. In this mini-review, I summarize the current findings on the inflammasome that have been described in the field of Reproductive Biology and highlight the potential that the inflammasome has as a novel therapeutic option in this field. The topics covered in this review as it pertains to the inflammasome field cover the literature published on male and female infertility, endometriosis, preeclampsia, placental inflammation, and reproductive senescence.

Oral probenecid improves sperm motility in men with spinal cord injury

STUDY DESIGN

Prospective cohort study (twenty men with spinal cord injury [SCI]).

OBJECTIVE

Determine if administration of oral probenecid results in improved sperm motility in men with SCI.

SETTING

Major university medical center.

METHODS

Twenty men with SCI were administered probenecid for 4 weeks (250 mg twice a day for 1 week, followed by 500 mg twice a day for 3 weeks). Semen quality was assessed at three time points: pre-treatment, post-treatment (immediately after the 4-week treatment), and follow-up (4 weeks after the last pill was ingested).

RESULT(S)

Probenecid was well-tolerated by all subjects. Sperm motility improved in each subject after 4 weeks of oral probenecid. The mean percent of sperm with progressive motility increased from 19% to 26% (P < 0.05). A more striking increase was seen in the mean percent of sperm with rapid linear motility, from 5% to 17%, (P <0.001). This improvement continued into the four week follow up period. Similar improvements were seen in the total motile sperm count (15 million, 28 million, and 27 million at pre-treatment, post-treatment, and follow-up, respectively). Sperm concentration was not significantly different at pre-treatment, post-treatment, and follow-up, (52 million, 53 million and 53 million, respectively).

CONCLUSION

This study showed that administration of an oral agent (probenecid) known to interfere with the pannexin-1 cellular membrane channel, can improve sperm motility in men with spinal cord injury. It is the first study to report improved sperm motility after oral medication in men with SCI.

Spinal cord injury and male infertility-a review of current literature, knowledge gaps, and future research

Spinal cord injury (SCI) affects nearly half a million new patients worldwide, with 17,700 in the US each year, and disproportionately impacts young males of reproductive age. Almost every aspect of male reproduction is affected by SCI, resulting in: erectile, endocrine and sexual dysfunction, decreased sperm motility despite an often-normal count, and abnormal semen emission and ejaculation. The aim of this review is to focus on how SCI impacts testicular spermatogenesis, sperm function, semen quality, and overall fecundity while discussing what is not known, and future avenues for research.

Lipid Peroxidation and Its Role in the Expression of NLRP1a and NLRP3 Genes in Testicular Tissue of Male Rats: a Model of Spinal Cord Injury

Background:

The majority of male patients with spinal cord injury (SCI) suffer from infertility. Nucleotide-binding oligomerization domain-like receptors NOD-like receptors (NLRs) are a kind of receptors that corporate in the inflammasome complex. Recent studies have introduced the inflammasome as the responsible agent for secreting cytokines in semen. Reactive oxygen species (ROS) is one of the elements that trigger inflammasome activation. Genital infections in SCI can lead to ROS generation. We investigated the relation between lipid peroxidation and inflammasome complex activity in testicular tissue of SCI rats.

Methods:

Adult male rats (n=20), weighting 200-250 g, were included and divided into four groups: three experimental groups, including SCI1, SCI3, and SCI7, i.e. the rats were subjected to SCI procedure and sacrificed after one, three, and seven days, respectively and a control group. We performed a moderate, midline spinal contusion injury at thoracic level 10. The animals were anesthetized, and testes were collected for measurement of gene expression by real-time PCR. Caudal parts of epididymis were collected for malondialdehyde (MDA) measurement.

Results:

No NLRP1a mRNA overexpression was seen in the testes of control and SCI groups. After seven days from SCI surgery, NLRP3 mRNA expression was significantly increased in SCI7 animals (p ≤ 0.05). There was a significant difference in MDA level in SCI7 versus control group, as well as SCI1 and SCI3 animals (p ≤ 0.05).

Conclusion:

NLRP3 overexpression occurs due to the increased ROS production in testis tissue of SCI rats

Advances in the management of infertility in men with spinal cord injury

Couples with a spinal cord injured male partner require assisted ejaculation techniques to collect semen that can then be further used in various assisted reproductive technology methods to achieve a pregnancy. The majority of men sustaining a spinal cord injury regardless of the cause or the level of injury cannot ejaculate during sexual intercourse. Only a small minority can ejaculate by masturbation. Penile vibratory stimulation and electroejaculation are the two most common methods used to retrieve sperm. Other techniques such as prostatic massage and the adjunct application of other medications can be used, but the results are inconsistent. Surgical sperm retrieval should be considered as a last resort if all other methods fail. Special attention must be paid to patients with T6 and rostral levels of injury due to the risk of autonomic dysreflexia resulting from stimulation below the level of injury. Bladder preparation should be performed before stimulation if retrograde ejaculation is anticipated. Erectile dysfunction is ubiquitous in the spinal cord injured population but is usually easily managed and does not pose a barrier to semen retrieval in these men. Semen analysis parameters of men with spinal cord injury are unique for this population regardless of the method of retrieval, generally presenting as normal sperm concentration but abnormally low sperm motility and viability. When sperm retrieval is desired in this population, emphasis should be placed on initially trying the simple methods of penile vibratory stimulation or electroejaculation before resorting to more advanced and invasive surgical procedures.

Reproductive Health of Men with Spinal Cord Injury

Most men with spinal cord injury (SCI) are infertile due to a combination of erectile dysfunction, ejaculatory dysfunction, and abnormal semen quality. This article addresses issues that should be considered when managing the reproductive health of men with SCI. The authors present recommendations based on their decades of experience in managing the reproductive health of more than 1,000 men with SCI. Men with SCI face obstacles when pursuing sexual activity and/or biologic fatherhood. Hypogonadism and premature symptoms of aging may interfere with sexual function. Erectile dysfunction is prevalent in the SCI population, and treatments for erectile dysfunction in the general population are also effective in the SCI population. Most men with SCI cannot ejaculate with sexual intercourse. The procedures of penile vibratory stimulation (PVS) and/or electroejaculation (EEJ) are effective in obtaining an ejaculate from 97% of men with SCI. The ejaculate often contains sufficient total motile sperm to consider the assisted conception procedures of intrauterine insemination or even intravaginal insemination at home. If PVS and/or EEJ fail, sperm may be retrieved surgically from the testis or epididymis. Surgical sperm retrieval typically yields enough motile sperm only for in vitro fertilization with intracytoplasmic sperm injection. The majority of new cases of SCI occur in young men at the peak of their reproductive health. With proper medical management, these men can expect to experience active sexual lives and biologic fatherhood, if these are their goals. Numerous tools are available to physicians for helping these patients reach their goals.

Acidification changes affect the inflammasome in human nucleus pulposus cells

BACKGROUND

Interleukin (IL)-1β is involved in the pathology of intervertebral disc degeneration. Under normal conditions, IL-1β is present in cells in an inactive form (pro-IL-1β). However, under pathological conditions, pro-IL-1β is turned into its active form (IL-1β) by the inflammasome, a multi-protein complex of the innate immune response that activates caspase-1. Under conditions of degeneration, the disc experiences an environment of increased acidification. However, the implications of acidification on the innate immune response remain poorly explored.

METHODS

Here we have studied how pH changes in human nucleus pulposus cells affect inflammasome activation by immunoblot analysis of protein lysates obtained from nucleus pulposus cells that were exposed to different pH levels in culture.

RESULTS

In this study, we have found that in nucleus pulposus cells, with increased acidification, there was a decrease in inflammasome activation consistent with lower levels of active IL-1β. However, this effect at a pH of 6.5, the lowest pH level tested, was abrogated when cells were treated with IL-1β.

CONCLUSIONS

Taken together, these findings suggest that the inflammatory response through IL-1β experienced by the human disc is not initiated in nucleus pulposus cells when the stimulus is acidification.

The nucleic acid-sensing inflammasomes

Inflammasomes are oligomeric signaling complexes that promote caspase activation and maturation of proinflammatory cytokines. Structural and biophysical studies have shed light on the mechanisms of nucleic acid recognition and signaling complex assembly involving the AIM2 (absent in myeloma 2) and IFI16 (γ-interferon-inducible protein 16) inflammasomes. However, our understanding of the mechanisms of the NLRP3 (nucleotide-binding oligomerization-like receptor family, pyrin domain-containing protein 3) activation, either by nucleic acids or by other reported stimuli, has remained elusive. Exciting recent progress on the filament formation by the ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain) pyrin domain and the IFI16-double stranded DNA complex has established that the formation of higher order polymers is one of the general mechanisms for signaling platform assembly in innate immune system. The paradigm-changing discovery of the extracellular function of the NLRP3-ASC inflammasome has opened the door for therapeutic targeting the inflammasome filament formation for various clinical conditions. Future characterization of the canonical and non-canonical inflammasome complexes will undoubtedly reveal more surprises on their structure and function and enrich our understanding of the molecular mechanisms of ligand recognition, activation, and regulation.

Therapeutics targeting the inflammasome after central nervous system injury

Innate immunity is part of the early response of the body to deal with tissue damage and infections. Because of the early nature of the innate immune inflammatory response, this inflammatory reaction represents an attractive option as a therapeutic target. The inflammasome is a component of the innate immune response involved in the activation of caspase 1 and the processing of pro-interleukin 1β. In this article, we discuss the therapeutic potential of the inflammasome after central nervous system (CNS) injury and stroke, as well as the basic knowledge we have gained so far regarding inflammasome activation in the CNS. In addition, we discuss some of the therapies available or under investigation for the treatment of brain injury, spinal cord injury, and stroke.

Male fertility following spinal cord injury: an update

Spinal cord injury (SCI) occurs most often in young men at the peak of their reproductive health. The majority of men with SCI cannot father children naturally. Three major complications contribute to infertility in men with SCI: erectile dysfunction, ejaculatory dysfunction, and abnormal semen quality. Erectile dysfunction can be managed by regimens available to the general population, including oral administration of phosphodiesterase-5 (PDE-5) inhibitors, intracavernosal injections, vacuum devices, and penile prostheses. Semen may be obtained from anejaculatory men with SCI via the medically assisted ejaculation methods of penile vibratory stimulation (PVS) or electroejaculation (EEJ). Sperm retrieval is also possible via prostate massage or surgical sperm retrieval. Most men with SCI have abnormal semen quality characterized by normal sperm concentrations but abnormally low sperm motility and viability. Accessory gland dysfunction has been proposed as the cause of these abnormalities. Leukocytospermia is evident in most SCI patients. Additionally, elevated concentrations of pro-inflammatory cytokines and elevated concentrations of inflammasome components are found in their semen. Neutralization of these constituents has resulted in improved sperm motility. There is a recent and alarming trend in the management of infertility in couples with SCI male partners. Although many men with SCI have sufficient motile sperm in their ejaculates for attempting intrauterine insemination (IUI) or even intravaginal insemination, surgical sperm retrieval is often introduced as the first and only sperm retrieval method for these couples. Surgical sperm retrieval commits the couple to the most advanced, expensive, and invasive method of assisted conception: in vitro fertilization with intracytoplasmic sperm injection (IVF/ICSI). Couples should be informed of all options, including semen retrieval by PVS or EEJ. Intravaginal insemination or IUI should be considered when indicated.

A clear and present danger: inflammasomes DAMPing down disorders of pregnancy

BACKGROUND

When the normal progression of pregnancy is threatened, inflammatory processes are often amplified in order to minimize detrimental effects and eliminate noxious agents. Inflammasomes are unique, intracellular, multiprotein assemblies that enable caspase-1 mediated proteolytic processing of the proinflammatory cytokine interleukin-1β, levels of which are elevated in some forms of preterm birth and maternal metabolic disorders.

METHODS

A comprehensive review based on a search of PubMed and Medline for terms and combinations of terms incorporating 'inflammation', 'inflammasome', 'pregnancy', 'preterm birth', 'pre-eclampsia', 'interleukin-1', 'caspase-1' and others selected to capture key articles.

RESULTS

In the decade since the discovery of the inflammasome, between January 2002 and June 2014 over 2200 articles have been published. Articles in the reproductive field are scarce but there is clear evidence for a role of the inflammasome axis in pregnancy, preterm birth and the maternal metabolic syndrome.

CONCLUSION

Further investigations on the inflammasome in pregnancy are needed in order to elucidate the biology of this unique structure in reproduction. Coordination of maternal, fetal and placental aspects of inflammasome function will potentially yield new information on the detection and transduction of host and non-host signals in the inflammatory response.