Bta-miR-149-3p suppresses inflammatory response in bovine Sertoli cells exposed to microcystin-leucine arginine (MC-LR) through TLR4/NF-kB signaling pathway

This study explored the regulatory role of bta-miR-149-3p in the inflammatory response induced by microcystin-leucine arginine (MC-LR) exposure in bovine Sertoli cells. The research endeavored to enhance the comprehension of the epigenetic mechanisms underlying MC-LR-induced cytotoxicity in Sertoli cells and establish a foundation for mitigating these effects in vitro. In this study, we elucidated the regulatory mechanism of bta-miR-149-3p in the MC-LR-induced inflammatory response by verifying the target gene of bta-miR-149-3p through luciferase assays and treating the cells with a bta-miR-149-3p inhibitor for 24 h. The results demonstrate that nuclear factor κB (NF-κB) acts as a downstream target gene of bta-miR-149-3p, which inhibits the MC-LR-induced inflammatory response in bovine Sertoli cells. This inhibition occurs by regulating the downregulation of tight junction constitutive proteins of the blood-testis barrier (BTB) through the suppression of the TLR-4/NF-κB signaling pathway (p < 0.05) and the up-regulation of the adhesion junction protein β-catenin (p < 0.05). Notably, MC-LR exposure resulted in the up-regulation (p < 0.05) of inflammatory cytokines (IL-6, IL-1β, and NLRP3) and the down-regulation (p < 0.05) of BTB tight junction constitutive proteins (ZO-1, Occludin) in Sertoli cells. Furthermore, the BTB constitutive protein ZO-1 exhibited significant down-regulation in Sertoli cells pretreated with the bta-miR-149-3p inhibitor compared to controls (p < 0.05), while Occludin showed no significant difference from CTNNB1 (p > 0.05). In summary, our findings suggest that bta-miR-149-3p suppresses the MC-LR-induced inflammatory response and alterations in the expression of BTB proteins in bovine Sertoli cells by inhibiting the TLR-4/NF-κB signaling pathway.

Pro-inflammatory cytokines and reproductive hormone responses in bucks post-challenge with Mannheimia haemolytica A2 and its outer membrane protein

The lipopolysaccharide (LPS) endotoxin and outer membrane protein (OMP) are among the virulence factors of Gram-negative bacteria responsible for inducing pathogenicity in the infected host. OMP and LPS occur on the outer membrane of M. haemolytica A2, the primary aetiological agent of pneumonic mannheimiosis in small ruminants. While the LPS is known to mediate Gram-negative bacterial infection by activating downstream inflammatory pathways, the potential role of OMP during inflammatory responses remained unclear. Hence, this study determined the effect of the OMP of M. haemolytica A2 on the serum concentration of pro-inflammatory cytokines and the male reproductive hormones (testosterone and Luteinizing Hormone). We randomly assigned twelve bucks to three groups (n = 4 bucks each): Group 1 was challenged with 2 mL PBS buffer (pH 7.0) intranasally; Group 2 received 2 mL of 1.2 X 109 CFU/mL whole M. haemolytica A2 intranasally; and Group 3 received 2 mL of OMP extract obtained from 1.2 X 109 CFU/mL M. haemolytica A2 intramuscularly. Serum samples collected at pre-determined intervals were used for the quantitative determination of the pro-inflammatory cytokines (IL-1β, IL-6, and TNFα) and reproductive hormones (testosterone and LH) using commercial sandwich enzyme-linked immunosorbent assay (ELISA). The serum concentration of IL1β was initially increased within the first-hour post-challenge in Groups 2 and 3, followed by a significant decrease in concentration at 21d and 35d (p < 0.05) in Group 3. Only mild fluctuations in IL-6 occurred in group 2, as opposed to the 1.7-fold rapid increase in TNFα within 2 h post-challenge before decreasing at 6 h. An increase in pro-inflammatory cytokines was accompanied by an acute febrile response of 39.5 ± 0.38 °C (p < 0.05) at 2 h and 40.1 ± 0.29 °C (p < 0.05) at 4 h in Group 2 and Group 3, respectively. Serum testosterone decreased significantly (p < 0.05) in both treatment groups but remained significantly (p > 0.05) lower than in Group 1 throughout the study. There was a moderate negative association between testosterone and IL1β (r = -0.473; p > 0.05) or TNFα (r = -0.527; p < 0.05) in Group 2. Serum LH also showed moderate negative associations with TNFα in Group 2 (r = -0.63; p < 0.05) and Group 3 (r = -0.54; p > 0.05). The results of this study demonstrated that M. haemolytica A2 and its OMP produced marked alterations in serum levels of pro-inflammatory cytokines and male reproductive hormones. The negative correlations between serum testosterone and inflammatory cytokines would suggest the potential role of OMP in causing male infertility by mediating innate inflammatory responses to suppress testosterone production in bucks.

Transcription factor Dmrt1 triggers the SPRY1-NF-κB pathway to maintain testicular immune homeostasis and male fertility

Bacterial or viral infections, such as Brucella, mumps virus, herpes simplex virus, and Zika virus, destroy immune homeostasis of the testes, leading to spermatogenesis disorder and infertility. Of note, recent research shows that SARS-CoV-2 can infect male gonads and destroy Sertoli and Leydig cells, leading to male reproductive dysfunction. Due to the many side effects associated with antibiotic therapy, finding alternative treatments for inflammatory injury remains critical. Here, we found that Dmrt1 plays an important role in regulating testicular immune homeostasis. Knockdown of Dmrt1 in male mice inhibited spermatogenesis with a broad inflammatory response in seminiferous tubules and led to the loss of spermatogenic epithelial cells. Chromatin immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNA-seq) revealed that Dmrt1 positively regulated the expression of Spry1, an inhibitory protein of the receptor tyrosine kinase (RTK) signaling pathway. Furthermore, immunoprecipitation-mass spectrometry (IP-MS) and co-immunoprecipitation (Co-IP) analysis indicated that SPRY1 binds to nuclear factor kappa B1 (NF-κB1) to prevent nuclear translocation of p65, inhibit activation of NF-κB signaling, prevent excessive inflammatory reaction in the testis, and protect the integrity of the blood-testis barrier. In view of this newly identified Dmrt1- Spry1-NF-κB axis mechanism in the regulation of testicular immune homeostasis, our study opens new avenues for the prevention and treatment of male reproductive diseases in humans and livestock.

Expression of CSF1, AR, and SRD5A2 during Postnatal Development of the Boar Reproductive Tract

Simple Summary

Understanding the initial development of the male reproductive system, including the prostate, should provide insight into malfunctions in the adult male. Although changes in circulating androgens during development are characterized in multiple species, potential changes in the androgen receptor, in the enzyme that converts testosterone to the presumably more potent dihydrotestosterone, and in colony stimulating factor 1, a critical mediator of macrophage influence on organ development, were previously unknown and anticipated to be influenced by androgens and estrogens. Gene expression in the testis, prostate, and seminal vesicles of these three mediators of development, including responses to reduced testosterone or estrogens, were evaluated. Each of these three genes had a unique temporal pattern of expression during postnatal reproductive tract development. However, surprisingly minimal effects of altered steroid signaling were reported on the expression of these presumed pivotal genes.

Abstract

The male reproductive system develops from a minimally functioning gonad and nonfunctioning accessory sex glands in the neonate; sex steroids, presumed to be primary influencers of these changes, have been characterized in multiple species. This study focused on the expression of the androgen receptor as the principal mediator of androgen-induced signaling; the 5α reductase enzyme that converts testosterone to the more active dihydrotestosterone; and colony stimulating factor 1, a mediator of macrophage influence on organ development in the pig. The time points chosen to evaluate normal developmental changes during the juvenile and prepubertal intervals included the inflection time points of 6.5 weeks of age at the nadir of circulating estradiol and testosterone concentrations in juveniles, and 11 weeks of age, when these concentrations begin to increase. The role of sex steroid signaling in the regulation of gene expression was evaluated by the blockade of androgen and estrogen receptors and reduction in endogenous estrogens. Expression of colony stimulating factor 1 in the testes gradually decreased during development; developmental profiles in the prostate and seminal vesicles were clearly different. Interference with sex steroid signaling had no effect on the expression of these three genes in testicular tissue and minimal and transient effects in prostate and seminal vesicles.

Seminal and histopathological alterations in bucks challenged with Mannheimia haemolytica serotype a2 and its LPS endotoxin

Pneumonic mannheimiosis is a widespread respiratory bacterial disease of small ruminants caused by Mannheimia haemolytica serotype A2. The disease is known to affect the respiratory organs of infected animals, but its effect on other vital and reproductive organs has not been fully explored. Previous studies have demonstrated increased serum pro-inflammatory cytokine concentration post-challenge with M. haemolytica A2 and its LPS, indicating systemic inflammation in the host. This study determined the potential tissue changes and alterations of sperm parameters due to infection of M. haemolytica A2 and its LPS endotoxin. In this study, twelve experimental bucks were randomly assigned to three groups of four bucks each: group 1 (control group) were intranasally inoculated with 2 mL of PBS pH 7.0, group 2 received 2 mL of 1.2 × 10⁹ CFU/mL M. haemolytica A2 intranasally, and group 3 received 2 mL of LPS extracted from 1.2 × 10⁹ CFU/mL of M. haemolytica A2 intravenously. Semen samples were collected at pre-determined intervals using an electro-ejaculator and analysed immediately after collection. All experimental bucks were slaughtered via exsanguination on day 60 to collect their vital and reproductive organs at necropsy, and the samples were processed and analysed for histopathological changes. The current study has revealed that bucks challenged with M. haemolytica A2 and its LPS exhibited alterations in semen parameters such as motility, wave pattern, viability, and morphological abnormalities. Mild to moderate histopathological changes of the lung, liver, testis, epididymis, vas deferens, prostate, and lymph nodes were also observed in both challenged groups. Therefore, this study revealed the potential harmful effects of respiratory mannheimiosis on the reproductive organs of the infected bucks and sheds light on the expanse of systemic effects of this disease.

NLRP3 inflammasome is involved in testicular inflammation induced by lipopolysaccharide in mice

PROBLEM

Systemic inflammation induced by infection, which is associated with testicular inflammation, predisposes males to subfertility. Recently, the nucleotide-binding oligomerization domain, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) inflammasome was identified as a key mediator of inflammation, and excessive activation of the NLRP3 inflammasome was shown to contribute to the pathogenesis of a wide variety of diseases. However, the mechanisms underlying infectious inflammation in the testis remain unclear. We investigated the effect of lipopolysaccharide (LPS)-induced systemic inflammation on the role of the NLRP3 inflammasome in murine testes.

METHOD OF STUDY

We performed in vivo and in vitro studies using an LPS-induced model of NLRP3 inflammasome activation and testicular inflammation.

RESULTS

Intraperitoneal administration of LPS significantly impaired sperm motility in the epididymis of wild type (WT) and NLRP3-knockout (KO) mice. LPS administration stimulated interleukin (IL)-1β production and secretion in the testes of WT mice, and these adverse effects were improved in the testes of NLRP3-KO mice. LPS administration also stimulated neutrophil infiltration as well as its chemoattractant C-C motif chemokine ligand 2 (CCL2) in WT testes, which were suppressed in NLRP3-KO testes. In in vitro cell culture, treatment with LPS and NLRP3 inflammasome activation significantly induced IL-1β and CCL2 secretion from WT but not NLRP3-KO testicular cells.

CONCLUSIONS

Taken together, our results suggest that testicular cells have the potential to secrete IL-1β and CCL2 in an NLRP3 inflammasome-dependent manner and that these cytokines from the testis may further exacerbate testicular function, resulting in subfertility during infectious diseases.

The ameliorative effect of melatonin on LPS-induced Sertoli cells inflammatory and tight junctions damage via suppression of the TLR4/MyD88/NF-κB signaling pathway in newborn calf

The blood-testicular barrier (BTB) is involved in spermatogenesis, protects sperm development, and plays a crucial role in the reproductive process. Tight junctions (TJs) between Sertoli cells (SCs) are the key structure of (BTB), and if its structure is damaged, BTB function is affected. The cellular inflammation caused by Gram-negative bacteria affects the structural integrity of TJs. Melatonin (MT) has anti-inflammatory effects; however, the effect of MT in newborn calf SCs is unknown. Therefore, this experiment studied the protective effect of MT. The results showed that LPS upregulated TLR4, MyD88, and NF-κB expressions, in turn, activated the TLR4/MyD88/NF-κB signaling pathway, produced a large amount of IL-6 and IL-1β, downregulated the expression of ZO-1 and Occludin, and reduced the viability of SCs, which resulted in the inflammatory response of SCs and damage of TJs. The addition of MT decreased TLR4, MyD88, and NF-κB expressions, it then inhibited the activation of TLR4/MyD88/NF-κB signaling pathway, downregulated the expression of IL-6 and IL-1β, upregulated the expression of ZO-1 and Occludin, and increased the cell viability, thereby alleviating the inflammatory response of SCs, and restored the TJs structure. Overall, our results reveal that MT can alleviate LPS-induced in newborn calf SCs Inflammation and TJs injury through TLR4/MyD88/NF-κB signaling pathway.

Bacterial Infections Affect Male Fertility: A Focus on the Oxidative Stress-Autophagy Axis

Numerous factors trigger male infertility, including lifestyle, the environment, health, medical resources and pathogenic microorganism infections. Bacterial infections of the male reproductive system can cause various reproductive diseases. Several male reproductive organs, such as the testicles, have unique immune functions that protect the germ cells from damage. In the reproductive system, immune cells can recognize the pathogen-associated molecular patterns carried by pathogenic microorganisms and activate the host's innate immune response. Furthermore, bacterial infections can lead to oxidative stress through multiple signaling pathways. Many studies have revealed that oxidative stress serves dual functions: moderate oxidative stress can help clear the invaders and maintain sperm motility, but excessive oxidative stress will induce host damage. Additionally, oxidative stress is always accompanied by autophagy which can also help maintain host homeostasis. Male reproductive system homeostasis disequilibrium can cause inflammation of the genitourinary system, influence spermatogenesis, and even lead to infertility. Here, we focus on the effect of oxidative stress and autophagy on bacterial infection in the male reproductive system, and we also explore the crosslink between oxidative stress and autophagy during this process.

The Effects of Sperm and Seminal Fluid of Immunized Male Mice on In Vitro Fertilization and Surrogate Mother-Embryo Interaction

The latest vaccination campaign has actualized the potential impact of antigenic stimuli on reproductive functions. To address this, we mimicked vaccination’s effects by administering keyhole limpet hemocyanin (KLH ) to CD1 male mice and used their sperm for in vitro fertilization (IVF). Two-cell embryos after IVF with spermatozoa from control (C) or KLH-treated (Im) male mice were transferred to surrogate mothers mated with vasectomized control (C) or KLH-treated (Im) male mice, resulting in four experimental groups: C–C, Im–C, C–Im, and Im–Im. The pre-implantation losses were significantly lower in the Im–C group than in the C–Im group. At the same time, the resorption rates reduced markedly in the C–Im compared to the Im–C group. Embryo and placenta weights were significantly higher in the Im–Im group. Although the GM-CSF levels were lower in the amniotic fluid of the gestating surrogate mothers in the Im–Im group, they were strongly correlated with embryo mass. The number–size trade-off was only significant in the Im–Im group. This suggests a positive, cooperative effect of spermatozoa and seminal fluid from immune-primed males on embryo growth and the optimal distribution of surrogate mother maternal resources despite the negative impact of males’ antigenic challenge on the IVF success rate.

Oxidative Stress, Testicular Inflammatory Pathways, and Male Reproduction

Inflammation is among the core causatives of male infertility. Despite male infertility being a serious global issue, "bits and pieces" of its complex etiopathology still remain missing. During inflammation, levels of proinflammatory mediators in the male reproductive tract are greater than usual. According to epidemiological research, in numerous cases of male infertility, patients suffer from acute or chronic inflammation of the genitourinary tract which typically occurs without symptoms. Inflammatory responses in the male genital system are inextricably linked to oxidative stress (OS). OS is detrimental to male fertility parameters as it causes oxidative damage to reproductive cells and intracellular components. Multifarious male infertility causative factors pave the way for impairing male reproductive functions via the common mechanisms of OS and inflammation, both of which are interlinked pathophysiological processes, and the occurrence of any one of them induces the other. Both processes may be simultaneously found in the pathogenesis of male infertility. Thus, the present article aims to explain the role of inflammation and OS in male infertility in detail, as well as to show the mechanistic pathways that link causative factors of male reproductive tract inflammation, OS induction, and oxidant-sensitive cellular cascades leading to male infertility.

MyD88 Is Not Required for Muscle Injury-Induced Endochondral Heterotopic Ossification in a Mouse Model of Fibrodysplasia Ossificans Progressiva

Excess inflammation and canonical BMP receptor (BMPR) signaling are coinciding hallmarks of the early stages of injury-induced endochondral heterotopic ossification (EHO), especially in the rare genetic disease fibrodysplasia ossificans progressiva (FOP). Multiple inflammatory signaling pathways can synergistically enhance BMP-induced Smad1/5/8 activity in multiple cell types, suggesting the importance of pathway crosstalk in EHO and FOP. Toll-like receptors (TLRs) and IL-1 receptors mediate many of the earliest injury-induced inflammatory signals largely via MyD88-dependent pathways. Thus, the hypothesis that MyD88-dependent signaling is required for EHO was tested in vitro and in vivo using global or Pdgfrα-conditional deletion of MyD88 in FOP mice. As expected, IL-1β or LPS synergistically increased Activin A (ActA)-induced phosphorylation of Smad 1/5 in fibroadipoprogenitors (FAPs) expressing Alk2^R206H. However, conditional deletion of MyD88 in Pdgfrα-positive cells of FOP mice did not significantly alter the amount of muscle injury-induced EHO. Even more surprisingly, injury-induced EHO was not significantly affected by global deletion of MyD88. These studies demonstrate that MyD88-dependent signaling is dispensable for injury-induced EHO in FOP mice.

Transient systemic inflammation in adult male mice results in underweight progeny

PROBLEM

While the testes represent an immune-privileged organ, there is evidence that systemic inflammation is accompanied by local inflammatory responses. We therefore examined whether transient systemic inflammation caused any inflammatory and functional consequences in murine testes.

METHOD OF STUDY

Using a single systemic administration of Toll-like receptor (TLR) agonists [lipopolysaccharide (LPS) or peptidoglycan (PG) or polyinosinic-polycytidylic acid (polyIC)] in young adult male mice, we assessed testicular immune-inflammatory landscape and reproductive functionality.

RESULTS

Our findings demonstrated a significant induction of testicular TNF-α, IL-1β and IL-6 transcripts within 24 h of TLR agonist injection. By day 6, these cytokine levels returned to baseline. While there was no change in caudal sperm counts at early time points, eight weeks later, twofold decrease in sperm count and reduced testicular testosterone levels were evident. When these mice were subjected to mating studies, no differences in mating efficiencies or litter sizes were observed compared with controls. Nonetheless, the neonatal weights of progeny from LPS/PG/polyIC-treated sires were significantly lower than controls. Postnatal weight gain up to three weeks was also slower in the progeny of LPS/polyIC-treated sires. Placental weights at 17.5 days post-coitum were significantly lower in females mated to LPS- and polyIC-treated males. Given this likelihood of an epigenetic effect, we found lower testicular levels of histone methyltransferase enzyme, mixed-lineage leukaemia-1, in mice given LPS/PG/polyIC 8 weeks earlier.

CONCLUSION

Exposure to transient systemic inflammation leads to transient local inflammation in the testes, with persistent sperm-mediated consequences for foetal development.

Toll-like receptor 4: A promising crossroads in the diagnosis and treatment of several pathologies

Toll-like receptor 4 (TLR4) is expressed in a wide variety of cells and is the central component of the mammalian innate immune system. Since its discovery in 1997, TLR4 has been assigned an ever-increasing number of functions that extend from pathogen recognition to tissue damage identification and promotion of the intrinsic "damage repair response" in pain, intestinal, respiratory and vascular disorders. Precisely, the finding of conserved sequence homology among species along with the molecular and functional characterisation of the TLR4 gene enabled researchers to envisage a common operating system in the activation of innate immunity and the initiation of plastic changes at the onset of chronic pain. Malfunctioning in other conditions was conceived in parallel. In this respect, "pivot" proteins and pathway redundancy are not just evolutionary leftovers but essential for normal functioning or cell survival. Indeed, at present, TLR4 single nucleotide polymorphisms (SNP) and their association with certain dysfunctions and diseases are being confirmed in different pools of patients. However, despite its ability to trigger pathogen infection or alternatively tissue injury communications to immune system, TLR4 targeting might not be considered a panacea. This review article represents a compilation of what we know about TLR4 from clinics and basic research on the 20th anniversary of its discovery. Understanding how to fine-tune the interaction between TLR4 and its specific ligands may lead in the next decades to the development of promising new treatments, reducing polypharmacy and probably having an impact on drug use in numerous pathologies.

Expression profile of Toll-like receptor 4 in rat testis and epididymis throughout postnatal development

Toll-like receptors (TLRs) belonging to pattern recognition receptors are involved in maintaining testicular and epididymal immune homeostasis. The purpose of the current study was to investigate TLR4 expression in rat testis and epididymis throughout postnatal development. Weak staining was detected in peritubular myoid cells and immature Sertoli cells while no staining was observed in gonocytes during prepubertal period. However, TLR4 expression began to appear in spermatocytes in pubertal period and gradually increased in spermatids. An intense staining was observed in steps 5-19 spermatids in post pubertal and mature periods. Similarly, TLR4 expression in the testes steadily increased from pubertal period to mature period. Puberty also caused a significant increase in TLR4 expression in epididymis. TLR4 expression in cauda epididymis was lower as compared to those of other epididymal segments. The majority of epididymal epithelial cells exhibited apical TLR4 expression, whereas basal cells showed intense intracytoplasmic immunoreaction. We detected an intense staining in epididymal smooth muscle cells. The expression levels of TLR4 showed dynamic changes in both spermatogenic cells, and entire testicular and epididymal tissues during postnatal development. These results suggest that TLR4 expression contributes not only to inflammation but also to the development of spermatogenic cells.

In "Vitro" Lps-Stimulated Sertoli Cells Pre-Loaded With Microparticles: Intracellular Activation Pathways

Sertoli cells (SC) are immune privileged cells with the capacity of modulating the immune response by expressing several immune-regulatory factors. SC have the capacity to respond to external stimuli through innate phagocytic and antibacterial activities. This evidence evoked a potential role of SC as drug carriers and therapeutic agents. Such stimuli drive SC towards a still unknown evolution, the clinical relevance of which as yet remains undisclosed. This study sought to investigate the effects of external stimuli in the form of polymeric microparticles (MP) and bacteria derived endotoxins, such as lipopolysaccharides (LPS), in order to identify the pathways potentially involved in cell phenotype modifications. Compared to single stimulation, when combined, MP and LPS provoked a significant increase in the gene expression of IDO, PD-L1, FAS-L, TLR-3, TLR-4, MHC-II, ICAM-1, TFGβ1, BDF123, BDF129, BDF3 and pEP2C. Western Blotting analysis demonstrated up-regulation of the ERK 1-2 and NF-kB p65 phosphorylation ratios. Our study, showing the exponential increase of these mediators upon combined MP and LPS stimulation, suggests a "switch" of SC function from typical cells of the blood-testicular barrier to nonprofessional tolerogenic antigen-presenting cells. Further studies should target the clinical and technological implications of such stimuli-induced SC transformation.

Immunological microenvironment in the testis

BACKGROUND

The testis is specific in that it produces haploid germ cells of which autoantigens newly appear long after the neonatal immune tolerance. Under normal condition, these autoantigens are protected by the blood-testis barrier formed by Sertoli cells. Thus, the testis is an immunologically privileged site where haploid cells are protected from autoimmune attack.

METHODS

The immunological microenvironment in the testis was experimentally investigated using mice and rats.

MAIN FINDINGS

Not only the blood-testis barrier but also various immuno-suppressive factors are involved in the immune-privileged testis. Indeed, germ cells transplanted into the xenogeneic seminiferous tubules could proliferate and differentiate with no aid of artificial immunosuppression. On the other hand, autoimmune orchitis could be experimentally produced by various methods of immunization with syngeneic or xenogeneic germ cell antigens.

CONCLUSION

Our results indicate that the testis is immunologically privileged but also immunologically fragile organ. Therefore, the dual nature is critical for immunoregulation of testicular function.

Systemic LPS induces toll-like receptor 3 (TLR3) expression and apoptosis in testicular mouse tissue

It is well known that sepsis and inflammation reduce male fertility. Within the testis, toll-like receptor 3 (TLR3) is constitutively expressed and recognizes double-stranded RNA (dsRNA) from viruses, degraded bacteria, damaged tissues and necrotic cells. To characterize the potential role of TLR3 in response to testicular infections, its expression and downstream signaling were investigated upon challenge with lipopolysaccharides (LPS) in two mouse strains that differ in their immuno-competence regarding T cell-regulated immunity. Thereto, Balb/c and Foxn1nu mice were randomized into six interventional groups treated with either i.v. application of saline or LPS followed by 20 min, 5 h 30 min and 18 h of observation and two sham-treated control groups. LPS administration induced a significant stress response; the amplification was manifested for TLR3 and interleukin 6 (IL6) mRNA in the impaired testis 5 h 30 min after LPS injection. TLR3 immunostaining revealed that TLR3 was primarily localized in spermatocytes. The TLR3 expression displayed different temporal dynamics between both mouse strains. However, immunofluorescence staining indicated only punctual interferon regulatory factor 3 (IRF3) expression upon LPS treatment along with minor alterations in interferon β (IFNβ) mRNA expression. Induction of acute inflammation was closely followed by a significant shift of the Bax/Bcl2 ratio to pro-apoptotic signaling accompanied by augmented TUNEL-positive cells 18 h after LPS injection with again differing patterns in both mouse strains. In conclusion, this study shows the involvement of TLR3 in response to LPS-induced testicular inflammation in immuno-competent and -incompetent mice, yet lacking transmission into its signaling pathway.

Pharmacological inhibition of TLR4/NF-κB with TLR4-IN-C34 attenuated microcystin-leucine arginine toxicity in bovine Sertoli cells

This study investigated the pharmacological inhibition of the toll-like receptor 4 (TLR4) genes as a measure to attenuate microcystin-LR (MC-LR) reproductive toxicity. Bovine Sertoli cells were pretreated with TLR4-IN-C34 (C34) for 1 hour. Thereafter the pretreated and non-pretreated Sertoli cells were cultured in medium containing 10% heat-activated fetal bovine serum + 80 μg/L MC-LR for 24 hours to assess the ability of TLR4-IN-C34 to attenuate the toxic effects of MC-LR. The results showed that TLR4-IN-C34 inhibited MC-LR-induced mitochondria membrane damage, mitophagy and downregulation of blood-testis barrier constituent proteins via TLR4/nuclear factor-kappaB and mitochondria-mediated apoptosis signaling pathway blockage. The downregulation of the mitochondria electron transport chain, energy production and DNA replication related genes (mt-ND2, COX-1, COX-2, ACAT, mtTFA) and upregulation of inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor-α, IL-1β, interferon-γ, IL-4, IL-10, IL-13 and transforming growth factor β1) were modulated by TLR4-IN-C34. Taken together, we conclude that TLR4-IN-C34 inhibits MC-LR-related disruption of mitochondria membrane, mitophagy and downregulation of blood-testis barrier proteins of the bovine Sertoli cell via cytochrome c release and TLR4 signaling blockage.

Sodium Selenite inhibits mitophagy, downregulation and mislocalization of blood-testis barrier proteins of bovine Sertoli cell exposed to microcystin-leucine arginine (MC-LR) via TLR4/NF-kB and mitochondrial signaling pathways blockage

This study was conducted to investigate the ameliorative effect of selenium on microcystin-LR induced toxicity in bovine Sertoli cells. Bovine Sertoli cells were pretreated with selenium (Na₂SeO₃) for 24 h after which selenium pretreated and non-pretreated Sertoli cells were cultured in medium containing 10% heat activated fetal bovine serum FBS+ 80 µg/L MC-LR to assess its ameliorative effect on MC-LR toxicity. The results show that selenium pretreatment inhibited the MC-LR induced mitophagy, downregulation and mislocalization of blood-testis barrier constituent proteins in bovine Sertoli cells via NF-kB and cytochrome c release blockage. The observed downregulation of electron transport chain (ETC) related genes (mt-ND2, COX-1, COX-2) and upregulation of inflammatory cytokines (IL-6, TNF-α, IL-1β, IFN-γ, IL-4, IL-10, 1 L-13, TGFβ1) in non-pretreated cells exposed to MC-LR were ameliorated in selenium pretreated cells. There was no significant difference (P > 0.05) in the protein levels of blood-testis barrier constituent proteins (ZO-1, occludin, connexin-43, CTNNB1, N-cadherin) and mitochondria related genes (mt-ND2, COX-1, COX-2, ACAT1, mtTFA) of selenium pretreated Sertoli cell compared to the control. Taken together, we conclude that selenium inhibits MC-LR caused Mitophagy, downregulation and mislocalization of blood-testis barrier proteins of bovine Sertoli cell via mitochondrial and TLR4/NF-kB signaling pathways blockage.

Effects of lipopolysaccharide-induced inflammation on hypoxia and inflammatory gene expression pathways of the rat testis

Background

Bacterial infection and inflammation of the testis impairs fertility, yet an understanding of inflammatory responses of the testis is incomplete. We are interested in identifying gene pathways involved in the detection and clearance of infectious microbes in the male reproductive tract. In previous studies in our lab focused on hypoxia-responsive genes of the testis, preliminary experiments suggested that genes classically categorized as hypoxia genes are also activated during antimicrobial responses. The purpose of this study was to identify hypoxia and inflammatory gene pathways that contribute to antimicrobial protection of the testis and to consider possible cross-talk and interactions between these pathways. Inflammation was induced in Sprague-Dawley rats using P. aeruginosa or E. coli lipopolysaccharide (LPS). Levels of hypoxia-inducible factor-1 (HIF-1α) protein and nuclear factor kappa B (NF-κB) were measured, and hypoxia and inflammatory gene expression patterns in testis were analyzed by gene expression profiling using real-time quantitative PCR arrays.

Results

In LPS-treated rats, HIF-1α protein increased with no change in Hif-1α mRNA. Western Blot analysis also demonstrated no change in NF-κB and inhibitory NFKB alpha (IκBα) protein levels following LPS treatment. Five hypoxia pathway genes (Angptl4, Egr1, Ier3, Pai1, and Glut1), and 11 inflammatory pathway genes (Ccl12, Cc13, Cd14, Cxcl10, Icam1, Il10, Il1b, Il6, Nfkbia, Tlr2, Tnf) up-regulated after 3 h of inflammation. Angptl4, Ccl12, Cc13, Cd14, Egr1, Nfkbia, Tlr2, and Tnf remained elevated at 6 h. Six genes were up-regulated at 6 h only (Bhlhe40, C3, Jak2, Nlrp3, Slc11a1, Tlr1). One gene (Tlr5) was down-regulated after 3 h and no genes at 6 h. Electrophoretic mobility shift assay results suggest a decrease in NF-κB binding activity following LPS treatment.

Conclusions

Testicular HIF-1α is up-regulated following LPS-induced inflammation. In contrast to other tissues, in which HIF-1α is up-regulated through transcriptional activation via NF-κB, we conclude that HIF-1α in the testis is not up-regulated through an increase in Hif-1α mRNA or through NF-κB-dependent mechanisms. Hypoxia pathway genes and genes involved in Toll-like receptor (TLR) and cytokine-mediated signaling comprise major functional categories of up-regulated genes, demonstrating that both hypoxia and classic inflammatory pathways are involved in inflammatory responses of the testis.

Electronic supplementary material

The online version of this article (10.1186/s12610-018-0079-x) contains supplementary material, which is available to authorized users.

Microcystin-leucine arginine (MC-LR) induced inflammatory response in bovine sertoli cell via TLR4/NF-kB signaling pathway

Sertoli cells were treated with 0, 20, 40, 60 and 80 μg/L of MC-LR to investigate its toxic effects, mechanism of action and immune response of the cells. Our results revealed that treatment containing 20 μg/L of MC-LR was non-toxic to the cells. Treatments containing 40, 60 and 80 μg/L of MC-LR reduced the cell viability, induced nuclear morphological changes and downregulated the blood-testis barrier constituent proteins within 48 h after treatment. The toll-like receptor 4 (TLR4) and nuclear factor-kappaB (NF-kB) were activated and significantly (P < 0.05) upregulated in cells treated with 40, 60 and 80 μg/L of MC-LR compared to the control. The pro-inflammatory cytokines were upregulated within 48 h after treatment. However commencing from 72 h, upregulation of anti-inflammatory cytokines and expression of blood-testis barrier constituent proteins was observed. This study indicates that MC-LR induced inflammatory response in bovine Sertoli cell via activation of TLR4/NF-kB signaling pathway.

Infectious, inflammatory and 'autoimmune' male factor infertility: how do rodent models inform clinical practice?

BACKGROUND

Infection and inflammation of the reproductive tract are significant causes of male factor infertility. Ascending infections caused by sexually transmitted bacteria or urinary tract pathogens represent the most frequent aetiology of epididymo-orchitis, but viral, haematogenous dissemination is also a contributory factor. Limitations in adequate diagnosis and therapy reflect an obvious need for further understanding of human epididymal and testicular immunopathologies and their contribution to infertility. A major obstacle for advancing our knowledge is the limited access to suitable tissue samples. Similarly, the key events in the inflammatory or autoimmune pathologies affecting human male fertility are poorly amenable to close examination. Moreover, the disease processes generally have occurred long before the patient attends the clinic for fertility assessment. In this regard, data obtained from experimental animal models and respective comparative analyses have shown promise to overcome these restrictions in humans.

OBJECTIVE AND RATIONALE

This narrative review will focus on male fertility disturbances caused by infection and inflammation, and the usefulness of the most frequently applied animal models to study these conditions.

SEARCH METHODS

An extensive search in Medline database was performed without restrictions until January 2018 using the following search terms: 'infection' and/or 'inflammation' and 'testis' and/or 'epididymis', 'infection' and/or 'inflammation' and 'male genital tract', 'male infertility', 'orchitis', 'epididymitis', 'experimental autoimmune' and 'orchitis' or 'epididymitis' or 'epididymo-orchitis', antisperm antibodies', 'vasectomy'. In addition to that, reference lists of primary and review articles were reviewed for additional publications independently by each author. Selected articles were verified by each two separate authors and discrepancies discussed within the team.

OUTCOMES

There is clear evidence that models mimicking testicular and/or epididymal inflammation and infection have been instructive in a better understanding of the mechanisms of disease initiation and progression. In this regard, rodent models of acute bacterial epididymitis best reflect the clinical situation in terms of mimicking the infection pathway, pathogens selected and the damage, such as fibrotic transformation, observed. Similarly, animal models of acute testicular and epididymal inflammation using lipopolysaccharides show impairment of reproduction, endocrine function and histological tissue architecture, also seen in men. Autoimmune responses can be studied in models of experimental autoimmune orchitis (EAO) and vasectomy. In particular, the early stages of EAO development showing inflammatory responses in the form of peritubular lymphocytic infiltrates, thickening of the lamina propria of affected tubules, production of autoantibodies against testicular antigens or secretion of pro-inflammatory mediators, replicate observations in testicular sperm extraction samples of patients with 'mixed atrophy' of spermatogenesis. Vasectomy, in the form of sperm antibodies and chronic inflammation, can also be studied in animal models, providing valuable insights into the human response.

WIDER IMPLICATIONS

This is the first comprehensive review of rodent models of both infectious and autoimmune disease of testis/epididymis, and their clinical implications, i.e. their importance in understanding male infertility related to infectious and non-infectious/autoimmune disease of the reproductive organs.

Male genital tract immune response against Chlamydia trachomatis infection

Chlamydia trachomatis is the most commonly reported agent of sexually transmitted bacterial infections worldwide. This pathogen frequently leads to persistent, long-term, subclinical infections, which in turn may cause severe pathology in susceptible hosts. This is in part due to the strategies that Chlamydia trachomatis uses to survive within epithelial cells and to evade the host immune response, such as subverting intracellular trafficking, interfering signaling pathways and preventing apoptosis. Innate immune receptors such as toll-like receptors expressed on epithelial and immune cells in the genital tract mediate the recognition of chlamydial molecular patterns. After bacterial recognition, a subset of pro-inflammatory cytokines and chemokines are continuously released by epithelial cells. The innate immune response is followed by the initiation of the adaptive response against Chlamydia trachomatis, which in turn may result in T helper 1-mediated protection or in T helper 2-mediated immunopathology. Understanding the molecular mechanisms developed by Chlamydia trachomatis to avoid killing and host immune response would be crucial for designing new therapeutic approaches and developing protective vaccines. In this review, we focus on chlamydial survival strategies and the elicited immune responses in male genital tract infections.

MKP-1 attenuates LPS-induced blood-testis barrier dysfunction and inflammatory response through p38 and IκBα pathways

Sertoli cells create a local tolerogenic microenvironment to maintain testicular immune privilege especially through the formation of a blood-testis barrier (BTB). However, the molecular mechanisms underlying the immune modulation function and BTB dynamics of Sertoli cells remained elusive. MAP phosphatase (MKP)-1 acts as a crucial negative regulator of the inflammatory response. Nevertheless, the role of MKP-1 in regulating Sertoli cells has not been elucidated. In this study, we have for the first time uncovered distinct cellular localization of MKP-1 in the cells at different stages of mouse testis, and the level of MKP-1 expression was significantly up-regulated by LPS-induced acute testis inflammation. In addition, MKP-1 staining was strongly detected in nuclei and peri-nuclear regions of cytoplasm in the Sertoli cells, and it was presented at Sertoli cell tight junctions (TJs) at stages VII-VIII after LPS treatment. Moreover, we demonstrated that MKP-1 was capable of attenuating LPS-induced decrease of occludin by interaction with p38 MAP kinase and IκBα molecules. Taken together, our data highlight that MKP-1 was an important endogenous suppressor of innate immune responses involved in the regulation of BTB barrier dynamic. This study thus might offer novel targets for treating inflammatory diseases in the testis.

The Expression of TLR2 and TLR3 in Sertoli Cells of Azoospermic Patients

Objective

Toll-like receptors (TLRs) on Sertoli cells are thought to have essential roles in sperm protection. This study was conducted to investigate the expression of TLR2 and TLR3 in Sertoli cells of men with azoospermia.

Materials and Methods

In this experimental study, testicular biopsies were taken from ten azoospermic men. Following enzymatic dissociation, the samples were moved to lectin coated petri dishes. After a few passages, all cells were cultivated and Seroli cells were sorted by flow cytometry. To confirm Sertoli cell purification, alkaline phosphatase activity (ALP) and immunohistochemistry assays were employed. The expression of TLR2 and TLR3 at the transcript and protein levels was examined with real-time quantitative reverse transcription-polymerase chain reaction (RT-QPCR) and western blot, respectively.

Results

Isolation, purification and cultivation of human Sertoli cells were performed successfully. Efficacy of purification of Sertoli cells by fluorescence-activated cell sorting (FACS) sorter was ~97%. The type of cultured cells was confirmed by vimentin and follicle-stimulating hormone (FSH) receptor markers. Furthermore, the existence of anti- Müllerian hormone in culture was confirmed. RT-PCR showed that both genes were expressed in Sertoli cells. Consistently, proteins of both were also expressed in Sertoli cells. Moreover, QPCR showed that the relative expression of TLR3 transcripts was significantly higher than TLR2 in Sertoli cells. Although both genes are expressed in fibroblast cells, their level of expression was significantly lower than in Sertoli cells.

Conclusion

This study confirmed expression of TLR2 and TLR3 in human Sertoli cells. This may be an indicator of their roles in developing immunity against pathogens as well as allo- and auto-antigens or viral antigens in seminiferous tubules.

Local Actions of Melatonin in Somatic Cells of the Testis

The pineal hormone melatonin regulates testicular function through the hypothalamic-adenohypophyseal axis. In addition, direct actions of melatonin in somatic cells of the testis have been described. Melatonin acts as a local modulator of the endocrine activity in Leydig cells. In Sertoli cells, melatonin influences cellular growth, proliferation, energy metabolism and the oxidation state, and consequently may regulate spermatogenesis. These data pinpoint melatonin as a key player in the regulation of testicular physiology (i.e., steroidogenesis, spermatogenesis) mostly in seasonal breeders. In patients with idiopathic infertility, melatonin exerts anti-proliferative and anti-inflammatory effects on testicular macrophages, and provides protective effects against oxidative stress in testicular mast cells. Consequently, melatonin is also involved in the modulation of inflammatory and oxidant/anti-oxidant states in testicular pathology. Overall, the literature data indicate that melatonin has important effects on testicular function and male reproduction.

Human sperm Toll-like receptor 4 (TLR4) mediates acrosome reaction, oxidative stress markers, and sperm parameters in response to bacterial lipopolysaccharide in infertile men

PURPOSE

To study the role of Toll-like receptor 4 (TLR4) in human spermatozoa and to assess sperm parameters, oxidative stress markers, and acrosome reaction in response to the stimulation of TLR4 by its ligand, the lipopolysaccharide (LPS), as a major endotoxin of Gram-negative bacteria.

METHODS

Our study was carried out in 73 sperm samples from patients undergoing semen analysis for couple infertility investigations. The studied patients were divided into three groups: normozoospermic fertile patients (n = 13), patients with abnormal and leukospermic semen (n = 13), and patients with abnormal and non-leukospermic semen (n = 47). TLR4 expression in human spermatozoa was initially analyzed by western blot. Sperm samples were incubated in the presence of LPS (200 ng/ml) for 18 h. Then, sperm motility and vitality were evaluated by microscopic observation and oxidative stress markers as malondialdehyde (MDA) and carbonyl groups (CG) were spectrophotometrically assessed in neat and selected sperm. A triple-stain technique was also performed to evaluate acrosome reaction in 15 sperm samples from infertile patients.

RESULTS

TLR4 expression was confirmed in human spermatozoa with a molecular weight of 69 kDa. In the normozoospermic group, no significant differences in sperm parameters and oxidative stress markers were shown after incubation with LPS in neat and selected sperms. Regarding samples from the non-leukospermic group, LPS reduced spermatozoa motility and vitality rates in selected sperm (P = 0.003; P = 0.004, respectively). A significant increase of MDA and CG levels was also detected (P = 0.01; P = 0.02, respectively). However, only the MDA levels were significantly increased (P = 0.01) in neat LPS-stimulated sperm. The same results were shown within the leukospermic group. The comparison between the two groups, leukospermic and non-leukospermic, in selected sperms showed a more important LPS effect in the leukospermic group significantly on motility and MDA rates (P = 0.006; P = 0.009, respectively). Furthermore, a significant decrease in reacted spermatozoa rate was detected in response to LPS in selected sperm samples from infertile men (P = 0.03).

CONCLUSIONS

These findings indicate that human spermatozoa express TLR4 and respond to LPS stimulation with alterations in viability, motility, and the acrosome reaction implicating reactive oxygen species (ROS) production in sperm samples from infertile patients.

Phenolic 1,3-diketones attenuate lipopolysaccharide-induced inflammatory response by an alternative magnesium-mediated mechanism

BACKGROUND AND PURPOSE

Toll-like receptor 4 (TLR4) plays a key role in the induction of inflammatory responses both in peripheral organs and the CNS. Curcumin exerts anti-inflammatory functions by interfering with LPS-induced dimerization of TLR4-myeloid differentiation protein-2 (MD-2) complex and suppressing pro-inflammatory mediator release. However, the inhibitory mechanism of curcumin remains to be defined.

EXPERIMENTAL APPROACH

Binding of bis-demethoxycurcumin (GG6) and its cyclized pyrazole analogue (GG9), lacking the 1,3-dicarbonyl function, to TLR4-MD-2 was determined using molecular docking simulations. The effects of these compounds on cytokine release and NF-κB activation were examined by ELISA and fluorescence staining in LPS-stimulated primary microglia. Interference with TLR4 dimerization was assessed by immunoprecipitation in Ba/F3 cells.

KEY RESULTS

Both curcumin analogues bound to the hydrophobic region of the MD-2 pocket. However, only curcumin and GG6, both possessing the 1,3-diketone moiety, inhibited LPS-induced TLR4 dimerization, activation of NF-κB and secretion of pro-inflammatory cytokines in primary microglia. Consistent with the ability of 1,3-diketones to coordinate divalent metal ions, LPS stimulation in a low magnesium environment decreased pro-inflammatory cytokine release and NF-κB p65 nuclear translocation in microglia and decreased TLR4-MD-2 dimerization in Ba/F3 cells. Curcumin and GG6 also significantly reduced cytokine output in contrast to the pyrazole analogue GG9.

CONCLUSIONS AND IMPLICATIONS

These results indicate that phenolic 1,3-diketones, with a structural motif able to coordinate magnesium ions, can modulate LPS-mediated TLR4-MD-2 signalling. Taken together, these studies identify a previously uncharacterized mechanism involving magnesium, underlying the inflammatory responses to LPS.

Surfactant protein D regulates murine testicular immune milieu and sperm functions

PROBLEM

Surfactant protein D (SP-D), a pattern recognition protein that regulates inflammation and immune homoeostasis, is expressed by testicular germ cells under the influence of testosterone. This study investigates the role of SP-D in testicular immune privilege and sperm functions.

METHOD OF STUDY

Testicular levels of cytokines and immunoregulatory molecules were evaluated in lipopolysaccharide (LPS)-challenged SP-D gene knockout mice (SP-D^-/- ). Further, sperm functions were assessed by computer-assisted sperm analyser (CASA) and in vitro capacitation. The effect of a recombinant fragment of human SP-D (rhSP-D) on LPS-induced testicular inflammation and sperm motility was assessed in wild-type (WT) mice.

RESULT

Endogenous absence of SP-D led to significantly increased testicular levels of immunosuppressive molecules, viz. serpina3, TGF-β1 and IL-10, and reduced levels of immune cell activation markers, CD86, IL-2 and ITGAX. These compensatory mechanisms resulted in markedly blunted levels of TNF-α, IL-12p40, MIP-1α, G-CSF and IL-6 in response to LPS challenge. Notably, exogenous supplementation of rhSP-D salvaged the WT mice from LPS-induced pro-inflammatory immune response and impairment of sperm motility by upregulating the levels of TGF-β1 and IL-10.

CONCLUSION

The study highlights the involvement of SP-D in maintenance of testicular immune privilege and its indirect contribution to male fertility.

Lipopolysaccharide Compromises Human Sperm Function by Reducing Intracellular cAMP

A worldwide decline in the quality of human semen is currently occurring. In mammals, sperm are produced from diploid stem-cell spermatogonia by spermatogenesis in testes and become mature in epididymis. Nevertheless, these biological processes can be affected by Gram-negative bacterial infection mediated by lipopolysaccharide (LPS), the major endotoxin of Gram-negative bacteria. It is well known that LPS can disturb spermatogenesis and affect sperm maturation and quality in vivo. However, the effect of LPS on the ejaculated mature sperm in vitro remains unclear. Thus, this study aimed to assess the in vitro toxicity of LPS on human sperm function and to elucidate the underlying mechanism. Human sperm were incubated with LPS (0.1-100 μg/ml) for 1-12 h in vitro and, subsequently, sperm viability, motility and capacitation, and the acrosome reaction were examined. LPS dose-dependently inhibited total and progressive motility and the ability to move through a viscous medium of the sperm but did not affect sperm viability, capacitation, and the acrosome reaction. To explore the underlying mechanism of LPS's actions, we examined the effects of LPS on the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca(2+)]i) and protein-tyrosine phosphorylation of human sperm, which are key regulators of human sperm function. LPS decreased intracellular cAMP dose-dependently but had no effect on [Ca(2+)]i and protein-tyrosine phosphorylation of human sperm. These findings suggest that LPS inhibits human sperm motility by decreasing intracellular cAMP.

IL-6 mediates differentiation disorder during spermatogenesis in obesity-associated inflammation by affecting the expression of Zfp637 through the SOCS3/STAT3 pathway

Zfp637 is a recently identified zinc finger protein, and its functions remain largely unknown. Here, we innovatively demonstrate the effects of Zfp637 on the differentiation of mouse spermatogonia and on its downstream target gene SOX2 in vitro. Obesity has been recognized as a chronic inflammatory disease that leads to decreased sexual function and sexual development disorders. We observed higher levels of IL-6 in serum and testis homogenates from obese mice compared with control mice. We also demonstrated that high levels of IL-6 inhibited Zfp637 expression, and we elucidated the underlying mechanisms. SOCS3 overexpression and STAT3 phosphorylation inhibitor (AG490) were used to investigate the function of the SOCS3/STAT3 pathway during this process. Our results showed that exposure of mouse spermatogonial cells to high levels of IL-6 inhibited Zfp637 expression by increasing SOCS3 expression and inhibiting the phosphorylation of STAT3, further reducing cellular differentiation. Consistent with the in vitro results, we observed increasing expression levels of SOCS3 and SOX2, but a reduction of Zfp637 expression, in obese mouse testes. In conclusion, Zfp637 plays a crucial role in spermatogenesis by downregulating SOX2 expression, and IL-6 can decrease the expression of Zfp637 through the SOCS3/STAT3 signaling pathway.

Cytokines release and oxidative status in semen samples from rabbits treated with bacterial lipopolysaccharide

This study was aimed to evaluate the effects of a lipopolysaccharide- (LPS) induced inflammation on cytokines release and oxidative status of semen samples from buck rabbits at different times after treatment. Semen analysis was performed by optical microscopy and sperm motility evaluation by the computer-assisted sperm analyzer. The presence of activated macrophages and apoptotic/necrotic sperm was evaluated by fluorescent microscopy. A panel of cytokines, interleukin (IL)-6, IL-8, IL-1β, and tumor necrosis factor-α, were detected and quantified in seminal plasma using the Bio-Plex Cytokine assay. Reactive oxygen metabolite and thiobarbituric acid-reactive substance determinations were carried out by spectrophotometry and tocopherol analysis by high performance liquid chromatography. The sperm motility and track speed were reduced in LPS-treated rabbits. The activated macrophages in LPS-treated buck rabbits significantly increased from 0.50 × 10(6)/mL (baseline) to 27 × 10(6)/mL on Day 21; successively, there was a progressive reduction. Apoptotic and necrotic sperm in LPS rabbits followed more or less the same trend. The reactive oxygen metabolite levels in semen from LPS-treated rabbits showed higher values compared with those evaluated in controls, particularly during the lag time, Days 1 to 3. The sperm thiobarbituric acid-reactive substances highlighted a peak in LPS-treated rabbits compared with those of controls on Day 1 after LPS treatment, and the different T isoforms (α, δ, and γ+β) showed a similar trend with a significant decrease on Day 1 after injection and a recovery on Days 30 to 56. Until Days 3 to 21 from the treatment, higher levels of IL-1β and tumor necrosis factor-α were detected in seminal plasma of LPS-treated rabbits. Interleukin-6 showed a peak on Day 3 after LPS treatment, and on Day 7, the value was similar to the control group. In conclusion, this study confirms that the buck rabbit is a good model for mimicking and understanding the inflammation mechanisms, which may induce male infertility, in particular that a systemic inflammatory status causes alterations to the sperm cells through a shift in the balance between the oxidant and antioxidant systems.

Targeting high mobility group box protein 1 ameliorates testicular inflammation in experimental autoimmune orchitis

STUDY QUESTION

Does high mobility group box protein 1 (HMGB1) regulate inflammatory reactions in a rat model of experimental autoimmune orchitis (EAO)?

SUMMARY ANSWER

HMGB1 appears to be involved in regulating inflammatory reactions in testes, as HMGB1 is translocated from testicular cells during the course of EAO and blocking its action by ethyl pyruvate (EP) reduces disease progression and spermatogenic damage.

WHAT IS KNOWN ALREADY

Despite its immune privileged status, the human testis is prone to inflammatory lesions associated with male factor infertility. Accumulating evidence shows that HMGB1 plays an important role in onset and progression of autoimmune diseases.

STUDY DESIGN, SIZE, DURATION

This is a cross sectional and longitudinal study involving Wistar male rats immunized with testicular homogenates to induce EAO 50 (EAO50; n = 10) and 80 (EAO80; n = 10) days after first immunization. Control adjuvant animals received saline instead of testicular homogenate (n = 16). Untreated animals (n = 10) were also studied. An interventional study was performed to block the action of HMGB1 starting 20 days after first immunization in EAO animals and respective controls (n = 17). Rats were treated i.p. with EP and the effect of EP treatment on testicular pathogenesis was evaluated 30 days later. Moreover, human testicular biopsies from infertile men with focal lymphocytic infiltrates (n = 7) and sections with intact spermatogenesis (n = 6) were probed with antibodies against HMGB1.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Testicular RNA and protein extracts from EAO animals, EAO animals treated with EP and relevant controls were used for analysis of cytokine expression by real-time RT-PCR and enzyme-linked immunosorbent assay. HMGB1 was co-localized on rat testicular cross sections with antibodies against testicular macrophages (TM), peritubular cells (PTC) and Sertoli cells (SC). Interaction of HMGB1 and its receptors (RAGE, TLR4) as well signaling pathways after HMGB1 stimulation were studied in isolated TM, PTC and SC by proximity ligation assay and western blot, respectively. Furthermore, HMGB1 immunofluorescence on human testicular biopsies was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

HMGB1 was translocated from the nuclei in EAO testes and testes of infertile men with impaired spermatogenesis and lymphocytic infiltrates. Elevated HMGB1 levels were observed during late phase of EAO. In testicular somatic cells HMGB1 receptors Toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE) were differentially expressed: HMGB1-TLR4 binding was predominant in TM, while HMGB1-RAGE interaction was prevalent in SC and PTC. In support, HMGB1 triggered extracellular signal regulated kinase (ERK)1/2 and cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) activation in SC and PTC, while TM responded to HMGB1 stimulation with p38 mitogen-activated protein kinase (MAPK) and p65 nuclear factor Kappa B (NF-ĸB) phosphorylation followed by increased tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) mRNA levels. In vivo treatment of EAO animals with EP 20 days after induction of disease revealed beneficial effects, as documented by reduced disease progression and spermatogenic damage, lower macrophage numbers, as well as decreased concentrations of HMGB1 and IL-6 in the testis compared with EAO controls.

LIMITATIONS, REASONS FOR CAUTION

The ability of HMGB1 to bind to a wide range of receptors makes it difficult to prevent its action by blockade of a specific receptor; therefore we applied EP, a drug preventing HMGB1 release from cells. Due to its mode of action EP decreases also the secretion of some other pro-inflammatory cytokines. Using isolated primary cells imposes limitations for cell transfection studies. As a compromise between purity and yield primary cells need to be isolated from animals of different age, which has to be considered when comparing their responses.

WIDER IMPLICATIONS OF THE FINDINGS

HMGB1 could be a promising target in attenuating testicular damage caused by inflammatory reactions.

Effect of chocolate and Propolfenol on rabbit spermatogenesis and sperm quality following bacterial lipopolysaccharide treatment

The aims of the study were to evaluate the effects of chocolate and propolis-enriched diets on rabbit spermatogenesis, sperm motility, and ultrastructure following bacterial lipopolysaccharide (LPS) treatment. Thirty-two New Zealand White rabbits were divided into four groups. The LPS-Propolfenol(®) group received propolis (500 mg/kg/day) in their diet for 15 days, while the LPS-chocolate group was fed 70% cacao chocolate (1 g/1 kg/day) for the same period. Following the diet treatments, rabbits in the LPS-Propolfenol(®) and LPS-chocolate groups, and an LPS group received a single intraperitoneal dose of 50 μg/kg LPS, and the control group received only saline. Kinematic sperm traits were evaluated with a computer assisted sperm analyzer (CASA) system, and ultrastructural characteristics were examined by transmission electron microscopy (TEM). Testicular and epididymal tissues were observed by light microscopy and TEM and multiplex real time reverse transcriptase-polymerase chain reaction (RT-PCR) assay was used to detect and quantify toll-like receptor-4 (TLR-4) gene expression. The values of the analyzed semen parameters of rabbits treated with LPS-Propolfenol(®) and LPS-chocolate did not show any variations compared with the control group, but they were lower in rabbits treated only with LPS. Alterations observed in the testicular tissue of LPS treated-rabbits were not detected in specimens from the LPS-chocolate and LPS-Propolfenol(®) groups, which showed normal spermatogenesis. The TLR-4 mRNA expression was similar in controls, in LPS treated, and in LPS-chocolate groups, but it was significantly (p < 0.01) decreased in LPS-Propolfenol(®) rabbits. In conclusion, a chocolate and propolis-enriched diet showed a protective effect on the spermatogenetic process of buck rabbits following LPS treatment.

Melatonin in testes of infertile men: evidence for anti-proliferative and anti-oxidant effects on local macrophage and mast cell populations

Melatonin acting through the hypothalamus and pituitary regulates testicular function. In addition, direct actions of melatonin at the testicular level have been recently suggested. We have described that melatonin inhibits androgen production in hamster Leydig cells via melatonin subtype 1a (mel1a) receptors and the local corticotrophin-releasing hormone (CRH) system. The initial events of the melatonin/CRH signalling pathway have also been established. Melatonin and all components of the melatonergic/CRH system were also detected in Leydig cells of infertile men. This study attempted to search for additional targets of melatonin in the human testis, and to investigate the effects of melatonin on proliferation and the oxidative state in these novel target cells. To this aim, evaluation of human testicular biopsies of patients suffering from hypospermatogenesis or Sertoli cell only syndrome and cell culture studies were performed. Melatonergic receptors were found in macrophages (MACs) and mast cells (MCs) of the human testis. In biopsies of patients suffering idiopathic infertility, melatonin testicular concentrations were negatively correlated with MAC number per mm(2) and TNFα, IL1β and COX2 expression, but positively correlated with the expression of the anti-oxidant enzymes SOD1, peroxiredoxin 1 and catalase. Melatonin inhibited proliferation and the expression of pro-inflammatory cytokines and cyclooxygenase 2 (COX2) in both the human non-testicular THP-1 MAC cell line and primary cell cultures of hamster testicular MACs. In the human HMC-1 MC line, melatonin increased the expression of anti-oxidant enzymes and decreased reactive oxygen species (ROS) generation. The results reveal new testicular targets of melatonin and describe anti-proliferative and anti-inflammatory effects of this hormone on testicular MACs. Furthermore, melatonin might provide protective effects against oxidative stress in testicular MCs.

Lipopolysaccharide inhibits the self-renewal of spermatogonial stem cells in vitro via downregulation of GDNF expression in Sertoli cells

Lipopolysaccharide (LPS) can reduce sperm count and sperm quality. The molecular mechanisms underlying this process are not fully understood. In this report, we investigated the effects of LPS-treated Sertoli cells on self-renewal and differentiation of spermatogoinial stem cells (SSCs). Sertoli cell cultures were established and incubated with LPS (10μg/ml) for 1, 2 or 3 days, respectively. The culture media were collected and used as conditioned media (CM) to culture SSCs. The expression of glial cell-derived neurotrophic factor (GDNF), stem cell factor (SCF) and bone morphogenetic protein 4 (BMP4) in Sertoli cells treated with LPS was analyzed by RT-PCR and Western blotting. The results showed that the expression of SSC differentiation markers, c-kit and Sohlh2, was increased, while the expression of SSC self-renewal markers, plzf, oct4, and PCNA, was repressed when cultured in CM from LPS-treated Sertoli cells. GDNF levels in Sertoli cells and CM reduced dramatically after LPS treatments, while SCF and BMP4 levels did not show any significant changes. Moreover, correlated with the GDNF levels in CM, GDNF target genes, Bcl6b and Etv5, were reduced markedly in SSCs. Our results suggest that LPS inhibits the expression of GDNF in Sertoli cells, and might prevent the SSC self-renewal via down-regulation of GDNF target genes.

RIG-I-like receptors mediate innate antiviral response in mouse testis

The testis is an immune privileged organ in which the tissue-specific cells have adopted effective innate immune functions against microbial pathogens. Toll-like receptors (TLRs) mediate innate immune response in the testis. The current study demonstrates that melanoma differentiation-associated protein 5 (MDA5) and retinoic acid-inducible gene I (RIG-I) initiate the testicular innate antiviral response. Both MDA5 and RIG-I are expressed in Leydig cells, and MDA5 is also expressed in spermatids. Polyinosinic-polycytidylic acid [poly(I:C)], a common agonist of MDA5 and RIG-I, significantly induces the expression of type I interferons (IFN-α/β) and antiviral proteins, including IFN-stimulated gene 15, 2'5'-oligoadenylate synthetase 1, and Mx GTPase 1, in primary TLR3-deficient (TLR3(-/-)) Leydig and germ cells. Moreover, major proinflammatory cytokines, including TNF-α and IL-6, are significantly up-regulated by poly(I:C) in these testicular cells. The poly(I:C)-induced innate antiviral response in the testicular cells is significantly reduced by knockdown of individual MDA5 and RIG-I using specific small interfering RNA. We also provide evidence that local injection of poly(I:C) induces antiviral response in the testis of TLR3(-/-) mice. These data provide novel insights into the mechanisms underlying testicular antiviral response.

Damaged spermatogenic cells induce inflammatory gene expression in mouse Sertoli cells through the activation of Toll-like receptors 2 and 4

Testicular inflammation, including noninfectious inflammatory responses in the testis, may impair male fertility. Mechanisms underlying the initiation of noninfectious testicular inflammation are poorly understood. In the current study, we demonstrate that damaged spermatogenic cell products (DSCPs) induce expression of various inflammatory mediators, including TNF-α, IL-1β, IL-6, and macrophage chemotactic protein 1 (MCP-1), in Sertoli cells. Notably, the DSCP-induced inflammatory gene expression was significantly reduced by knockout Toll-like receptor (TLR)2 or TLR4, and abolished by double knockout TLR2 and TLR4 (TLR2(-/-)TLR4(-/-)). MCP-1 secreted by Sertoli cells after stimulation with DSCPs promotes macrophage migration. We also provide evidence that busulfan-induced spermatogenic cell damages in vivo upregulate TNF-α and MCP-1 expression in Sertoli cells, and facilitate macrophage infiltration into the testis in wild-type mice. These phenomena were not observed in TLR2(-/-)TLR4(-/-) mice. Data indicate that DSCPs induce inflammatory gene expression in Sertoli cells via the activation of TLR2 and TLR4, which may initiate noninfectious inflammatory responses in the testis. The results provide novel insights into the mechanisms underlying damaged spermatogenic cell-induced testicular inflammation.

Regulation of activin and inhibin in the adult testis and the evidence for functional roles in spermatogenesis and immunoregulation

Activin A provides a unique link between reproduction and immunity, which is especially significant in the adult testis. This cytokine, together with inhibin B and follistatin acting as regulators of activin A activity, is fundamentally involved in the regulation of spermatogenesis and testicular steroidogenesis. However, activin A also has a much broader role in control of inflammation, fibrosis and immunity. In the Sertoli cell, activin A is regulated by signalling pathways that normally regulate stress and inflammation, signalling pathways that intersect with the classical hormonal regulatory pathways mediated by FSH. Modulation of activin A production and activity during spermatogenesis is implicated in the fine control of the cycle of the seminiferous epithelium. The immunoregulatory properties of activin A also suggest that it may be involved in maintaining testicular immune privilege. Consequently, elevated activin A production within the testis during inflammation and infection may contribute to spermatogenic failure, fibrosis and testicular damage.

Structural, cellular and molecular aspects of immune privilege in the testis

The testis presents a special immunological environment, considering its property of immune privilege that tolerates allo- and auto-antigens. Testicular immune privilege was once believed to be mainly based on the sequestration of antigens from the immune system by the blood–testis barrier in the seminiferous epithelium. Substantial evidence supports the view that the combination of physical structure, testicular cells, and cytokines controls immune responses in the testis to preserve the structural and functional integrity of testicular immune privilege. Both systemic immune tolerance and local immunosuppression help maintain the immune privilege status. Constitutive expression of anti-inflammatory factors in testicular cells is critical for local immunosuppression. However, the testis locally generates an efficient innate immune system against pathogens. Disruption of these mechanisms may lead to orchitis and impair fertility. This review article highlights the current understanding of structural, cellular, and molecular mechanisms underlying the unique immune environment of the testis, particularly its immune privilege status.

Toll-like receptor 3-initiated antiviral responses in mouse male germ cells in vitro

The testis is an immunoprivileged site where local cell-initiated innate immunity plays a crucial role in antimicrobial responses. Toll-like receptors (TLRs) mediate innate immune responses in testicular somatic cells. Although several TLRs are expressed in some stages of male germ cells, the potential role of TLRs in triggering antimicrobial responses in the germ cells has yet to be exclusively studied. The current study demonstrates that TLR3 is constitutively expressed in spermatogonia and spermatocytes and can be activated by a synthetic double-strained RNA analog, polyinosinic-polycytidylic acid. TLR3 activation in these male germ cells up-regulates the expression of proinflammatory cytokines, such as interleukin IL1B, IL6, and tumor necrosis factor alpha, through activation of nuclear factor kappa B; it also induces production of type 1 interferons (IFNA and IFNB) through the activation of IFN regulatory factor 3. In addition, TLR3 activation increases the production of two major antiviral proteins, namely, double-stranded RNA-activated protein kinase and MX1 protein, by germ cells. Data in this article describe an antiviral response of male germ cells through the activation of TLR3 in vitro.

Immunophysiology and pathology of inflammation in the testis and epididymis

The ability of spermatogenic cells to evade the host immune system and the ability of systemic inflammation to inhibit male reproductive function represent two of the most intriguing conundrums of male reproduction. Clearly, an understanding of the underlying immunology of the male reproductive tract is crucial to resolving these superficially incompatible observations. One important consideration must be the very different immunological environments of the testis, where sperm develop, and the epididymis, where sperm mature and are stored. Compared with the elaborate blood-testis barrier, the tight junctions of the epididymis are much less effective. Unlike the seminiferous epithelium, immune cells are commonly observed within the epithelium, and can even be found within the lumen, of the epididymis. Crucially, there is little evidence for extended allograft survival (immune privilege) in the epididymis, as it exists in the testis, and the epididymis is much more susceptible to loss of immune tolerance. Moreover, the incidence of epididymitis is considerably greater than that of orchitis in humans, and susceptibility to sperm antibody formation after damage to the epididymis or vas deferens increases with increasing distance of the damage from the testis. Although we still know relatively little about testicular immunity, we know less about the interactions between the epididymis and the immune system. Given that the epididymis appears to be more susceptible to inflammation and immune reactions than the testis, and thereby represents the weaker link in protecting developing sperm from the immune system, it is probably time this imbalance in knowledge was addressed.