Toxic effect on human spermatozoa by Chlamydia trachomatis purified lipopolysaccharide

Are sexually transmitted infections associated with male infertility? A systematic review and in-depth evaluation of the evidence and mechanisms of action of 11 pathogens

Purpose

To systematically review the evidence on the association between sexually transmitted infections (STIs) and male infertility. We sought to answer two questions: Are STIs significantly associated with detrimental changes in semen parameters?; and, is the prevalence of STIs significantly higher in infertile than fertile men?

Materials and methods

PubMed, Scopus and Google Scholar databases were searched (inceptionMarch 2023) following the PRISMA guidelines. Identified original studies in English on the association between STIs and male infertility were included. Data was tabulated/described by pathogen, mechanisms of action, number of studies and their level of evidence.

Results

Seventy out of 903 originally retrieved articles were included in this review. For the detrimental changes in semen parameters (first question), the evidence seems equivocal based on the nearly equal number of studies and similar levels of evidence. The only exception was for Ureaplasma, where the number of studies and levels of evidence supported an association with male infertility. Pertaining to a significantly higher prevalence of STI among infertile compared to fertile men (second question), evidence was insufficient to support/deny a significant association. The two exceptions were Ureaplasma and Mycoplasma, where the number of studies and evidence levels were in favour of an association with male infertility.

Conclusions

Generally, the relationship between STIs and male infertility remains to be uncovered. Our appraisal of the overall state of this relationship shows that the evidence base leaves much to be desired. The exceptions are Ureaplasma and Mycoplasma, where the evidence convincingly suggests their associations with infertility in men.

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.

Host cell death during infection with Chlamydia: a double-edged sword

The phylum Chlamydiae constitutes a group of obligate intracellular bacteria that infect a remarkably diverse range of host species. Some representatives are significant pathogens of clinical or veterinary importance. For instance, Chlamydia trachomatis is the leading infectious cause of blindness and the most common bacterial agent of sexually transmitted diseases. Chlamydiae are exceptionally dependent on their eukaryotic host cells as a consequence of their developmental biology. At the same time, host cell death is an integral part of the chlamydial infection cycle. It is therefore not surprising that the bacteria have evolved exquisite and versatile strategies to modulate host cell survival and death programs to their advantage. The recent introduction of tools for genetic modification of Chlamydia spp., in combination with our increasing awareness of the complexity of regulated cell death in eukaryotic cells, and in particular of its connections to cell-intrinsic immunity, has revived the interest in this virulence trait. However, recent advances also challenged long-standing assumptions and highlighted major knowledge gaps. This review summarizes current knowledge in the field and discusses possible directions for future research, which could lead us to a deeper understanding of Chlamydia's virulence strategies and may even inspire novel therapeutic approaches.

Bacterial infection of the male reproductive system causing infertility

Bacterial infections play a disruptive and hidden role in male reproductive failure. Different kinds of bacteria are often able to interfere with reproductive function in both sexes and lead to infertility. In this study, to further evaluate the role of bacterial infections in male reproduction we provided an extensive overview of so far researches investigating the effects of bacterial infections on male fertility. We searched Medline, PubMed, Scopus and Google scholar databases to identify the potentially relevant studies on bacterial infections and their implications in male infertility. All the bacteria included in this article have negative effects on the male reproductive function; however, there is ample evidence to blame bacteria such as Escherichia coli, Chlamydia trachomatis, Ureaplasma, Mycoplasma and Staphylococcus aureus for reduced fertility and deterioration of sperm parameters. More studies are needed to clarify the molecular mechanisms by which different bacteria exert their detrimental effects on male reproductive system. Getting more insight into probable mechanisms, would significantly facilitate the production of new, advanced, and effective remedies in the future. In view of all evidence, we strongly suggest increasing awareness among people and considering screening programs for patients seeking fertility both to avoid transmission and to improve fertility outcomes among them.

[Prevalence and role of IgG anti-Chlamydia trachomatis in a population of infertile men in Morocco]

INTRODUCTION

Infertility is a global public health problem that affects 15% of couples of childbearing age. Male infertility is involved in 20 to 50% of cases. These figures are sharply increasing around the world. Several factors may be responsible for this infertility with especially hormonal, genetic, toxic or infectious factors. The latter are dominated mainly by Chlamydia infection. Among the most serious complications of this infection are infertility related to urethritis, epididymitis and irreversible total azoospermia in men and tubal obstructions and ectopic pregnancies in women.

STUDY OBJECTIVE

To determine the prevalence of IgG anti-Chlamydia trachomatis in men consulting for infertility and the association between previous contact with this bacterium and the impairment of sperm quality and sperm function.

MATERIAL AND METHODS

Prospective study over 26months of 143 patients referred to the service for infertility assessment of the couple. Demographic data, primary or secondary character of infertility, risk factors (tobacco, inguinal hernia, varicocele and history of urogenital infections), semen parameters (volume, mobility, pH, vitality and morphological abnormalities) were studied as well as the determination of the anti-C. trachomatis IgG titer. The prevalence of Chlamydia infection and the association of the infection and alteration of the various parameters of the semen were analyzed.

RESULTS

The average age of patients was 38.5±8.55. Infertility was primary in 72% of patients. Among the patients, 54.5% had an abnormal spermogram. Chlamydia IgG antibodies were positive in 37.1% of patients whose 58.5% had abnormal spermogram. Analysis of sperm parameters of patients with and without IgG C. trachomatis showed an altered vitality in Chlamydia positive patients with an OR at 2.41, P=0.02, (95% CI: 1.15-5.06).

CONCLUSION

The prevalence of Chlamydia infection is high in infertile male. C. trachomatis IgG antibodies may be associated with an alteration of spermatozoa vitality without significant impairment of other semen parameters.

LEVEL OF EVIDENCE

3.

The Role of the Immune Response in Chlamydia trachomatis Infection of the Male Genital Tract: A Double-Edged Sword

Chlamydia trachomatis (CT) is the most prevalent bacterial sexually transmitted infection in the world, with more than 100 million cases reported annually. While there have been extensive studies into the adverse effects that CT infection has on the female genital tract, and on the subsequent ability of these women to conceive, studies into the consequences on male fertility have been limited and controversial. This is in part due to the asymptomatic nature of the infection, where it is estimated that 50% of men with Chlamydia fail to show any symptoms. It is accepted, however, that acute and/or persistent CT infection is the causative agent for conditions such as urethritis, epididymitis, epididymo-orchitis, and potentially prostatitis. As with most infections, the immune system plays a fundamental role in the body’s attempts to eradicate the infection. The first and most important immune response to Chlamydia infection is a local one, whereby immune cells such as leukocytes are recruited to the site of infections, and subsequently secrete pro-inflammatory cytokines and chemokines such as interferon gamma. Immune cells also work to initiate and potentiate chronic inflammation through the production of reactive oxygen species (ROS), and the release of molecules with degradative properties including defensins, elastase, collagenase, cathespins, and lysozyme. This long-term inflammation can lead to cell proliferation (a possible precursor to cancer), tissue remodeling, and scarring, as well as being linked to the onset of autoimmune responses in genetically disposed individuals. This review will focus on the ability of the immune system to recognize and clear acute and persistent chlamydial infections in the male genital tract, and on the paradoxical damage that chronic inflammation resulting from the infection can cause on the reproductive health of the individual.

Molecular detection of Chlamydia trachomatis and other sexually transmitted bacteria in semen of male partners of infertile couples in Tunisia: the effect on semen parameters and spermatozoa apoptosis markers

This study was undertaken to determine the prevalence of Chlamydia trachomatis, Mycoplasmas, and Ureaplasmas in semen samples of the male partners of infertile couples and to investigate whether Chlamydia trachomatis could initiate apoptosis in human spermatozoa. A total of 85 males partners of infertile couples undergoing routine semen analysis according to World Health Organization guidelines were included. Specimens were examined for the presence of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma hominis, Mycoplasma genitalium, Ureaplasma urealyticum and Ureaplasma parvum by Real time PCR (qPCR). Semen specimens were analysed for the appearance of apoptotic markers (sperm DNA fragmentation, activated caspase 3 levels, mitochondrial membrane potential (ΔΨm)) using flow cytometry. C. trachomatis, N. gonorrhoeae, U. urealyticum, M genitalium were detected in semen samples of 13 (15.2%), 5 (5.8%), 5 (5.8%) and 3 (3.5%) male partners of infertile couples, respectively. M. hominis and U. parvum were detected in semen sample of only one patient (1.1%). The semen of infertile men positive for C. trachomatis showed lower mean of semen count and lower rapid progressive motility (category [a]) of spermatozoa compared to uninfected men with statistically significances (p = 0.02 and p = 0.04, respectively). Flow cytometry analyses demonstrated a significant increase of the mean rate of semen with low ΔΨm and caspase 3 activation of infertile men positive for C. trachomatis compared to uninfected men (p = 0.006 and p = 0.001, respectively). DNA fragmentation was also increased in sperm of infertile men positive for C. trachomatis compared to uninfected men but without statistical significances (p = 0.62). Chlamydial infection was associated to loss of ΔΨm and caspase 3activation. Thus, C. trachomatis infection could be incriminated in apoptosis induction of spermatozoa. These effects may explain the negative direct impact of C. trachomatis infection on sperm fertilizing ability.

Chlamydia trachomatis infection of the male genital tract: an update

Chlamydia trachomatis (CT) is the most prevalent cause of sexually transmitted diseases. Although the prevalence of chlamydial infection is similar in men and women, current research and screening are still focused on women, who develop the most severe complications, leaving the study of male genital tract (MGT) infection underrated. Herein, we reviewed the literature on genital CT infection with special focus on the MGT. Data indicate that CT certainly infects different parts of the MGT such as the urethra, seminal vesicles, prostate, epididymis and testis. However, whether or not CT infection has detrimental effects on male fertility is still controversial. The most important features of CT infection are its chronic nature and the presence of a mild inflammation that remains subclinical in most individuals. Chlamydia antigens and pathogen recognition receptors (PRR), expressed on epithelial cells and immune cells from the MGT, have been studied in the last years. Toll-like receptor (TLR) expression has been observed in the testis, epididymis, prostate and vas deferens. It has been demonstrated that recognition of chlamydial antigens is associated with TLR2, TLR4, and possibly, other PRRs. CT recognition by PRRs induces a local production of cytokines/chemokines, which, in turn, provoke chronic inflammation that might evolve in the onset of an autoimmune process in genetically susceptible individuals. Understanding local immune response along the MGT, as well as the crosstalk between resident leukocytes, epithelial, and stromal cells, would be crucial in inducing a protective immunity, thus adding to the design of new therapeutic approaches to a Chlamydia vaccine.

Male infertility and genital chlamydial infection: victim or perpetrator?

The role of Chlamydia trachomatis in the cause of male infertility is under discussion. This paper attempts to summarize data from the literature, which support the role of C. trachomatis in male infertility or oppose this suggestion. The following observations are based on a survey of the literature: 1) Chlamydia trachomatis is a frequent pathogen in male genital inflammation, the micro-organisms are rarely present in healthy men. 2) Without doubt, C. trachomatis causes inflammations of the male urethra and the epididymis. Prostatitis and glandulitis vesicalis are discussed controversially. 3) Chlamydia trachomatis antigen or DNA is not demonstrable in secretions of the male accessory glands including the semen with sufficient reproducibility. However, it is easily demonstrable in urethral swabs and the urine. 4) Determination of chlamydial antibodies in serum or semen does not conclusively indicate a current infection with C. trachomatis. 5) There are no conclusive studies showing that men infected with C. trachomatis are less fertile than uninfected men. 6) The male genital chlamydial infection is a threat to the female genital organs, because C. trachomatis infection of the female genital organs may be deleterious to female fertility.

Chlamydia trachomatis-induced death of human spermatozoa is caused primarily by lipopolysaccharide

Elementary bodies (EBs) of Chlamydia trachomatis serovar E are more toxic to sperm than those from serovar LGV. In this study, lipopolysaccharide (LPS) was prepared from the EBs of both serovars and incubated with human spermatozoa at concentrations that matched the LPS concentration of EBs. The effects of EBs and LPS on sperm motility, viability and acrosomal status were then determined. Sperm motility was measured by computer-assisted sperm analysis and the hypo-osmotic swelling test was used to determine the proportion of dead cells. Acrosomal status was examined using a standard mAb assay. Over a 6 h incubation, LPS from both serovars resulted in a marked reduction in sperm motility (and a concomitant increase in the proportion of dead spermatozoa) in a manner similar to that seen in response to EBs of serovar E. In addition, when sperm were incubated with a range of doses of EBs and LPS, probit analysis revealed that the greater spermicidal effects of EBs from serovar E (when compared with serovar LGV) were not observed when sperm were incubated with LPS from the two serovars. This suggests that the more potent effect of EBs of serovar E cannot be explained entirely by differences in the composition of LPS. Interestingly, Escherichia coli LPS was required in doses 500 times more concentrated than chlamydial LPS in order to kill a similar proportion of sperm, suggesting that bacterial LPSs may differ in their spermicidal properties. However, that chlamydial LPS was spermicidal was demonstrated by the use of polymyxin B (a polycationic antibiotic known to neutralize LPS effects), confirming that the effects observed were primarily a result of LPS activity.