Innate immunity in the male genital tract: Chlamydia trachomatis induces keratinocyte-derived chemokine production in prostate, seminal vesicle and epididymis/vas deferens primary cultures

Long-term consequences of sexually transmitted infections on men's sexual function: A systematic review

Objective: To systematically review the available literature on the long-term effects of sexually transmitted diseases (STIs) on male reproductive functions.

Methods: A PubMed search was conducted on 3 January 2021, and as a result, 952 articles were retrieved. Exclusion of irrelevant articles resulted in 36 articles, dating from 1998 to 2020, which were analysed.

Results: Only 52.8% of these articles described original research, while the rest were reviews. The majority (26) of the articles dealt with bacterial infections, of which 20 described Chlamydia trachomatis. There were 11 articles that described research on viruses, with five on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The analysis of the articles showed further that not much new knowledge on the long-term effects on male reproductive functions has been added. The existing knowledge that ascending infections can cause epididymo-orchitis, prostatitis or urethritis was confirmed. Due to epithelial inflammatory responses these infections can result in scarring with resulting infertility due to obstruction. These effects were described for Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium or Treponema pallidum, as well as for the Zika and SARS-CoV-2 viruses. Even trichomoniasis can lead to long-term compromised male fertility if not treated.

Conclusion: In conclusion, problem awareness needs to be raised and more research on this important topic needs to be conducted.

Pattern recognition receptor-initiated innate immune responses in mouse prostatic epithelial cells‡

Three major pathogenic states of the prostate, including benign prostatic hyperplasia, prostate cancer, and prostatitis, are related to the local inflammation. However, the mechanisms underlying the initiation of prostate inflammation remain largely unknown. Given that the innate immune responses of the tissue-specific cells to microbial infection or autoantigens contribute to local inflammation, this study focused on pattern recognition receptor (PRR)-initiated innate immune responses in mouse prostatic epithelial cells (PECs). Primary mouse PECs abundantly expressed Toll-like receptor 3 (TLR3), TLR4, TLR5, melanoma differentiation-associated protein 5 (MDA5), and IFN-inducible protein 16 (p204 in mouse). These PRRs can be activated by their respective ligands: lipopolysaccharide (LPS) and flagellin of Gram-negative bacteria for TLR4 and TLR5, polyinosinic-polycytidylic acid (poly(I:C)) for TLR3 and MDA5, and herpes simplex virus DNA analog (HSV60) for p204. LPS and flagellin predominantly induced the expression of inflammatory cytokines, including tumor necrosis factor alpha (TNFA), interleukin 6 (IL6), chemokines monocyte chemoattractant protein-1 (MCP1), and C-X-C motif chemokine 10 (CXCL10). Poly(I:C) and HSV60 predominantly induced the expression of type 1 interferons (IFNA and IFNB) and antiviral proteins: Mx GTPase 1, 2',5'-oligoadenylate synthetase 1, and IFN-stimulated gene 15. The replication of mumps virus in PECs was inhibited by type 1 IFN signaling. These findings provide insights into the mechanisms underlying innate immune response in the prostate.

Prostate immunology: A challenging puzzle

Mucosal immunity defines the relationship of surfaces in contact with the environment and integrates diverse tissues such as epidermis, gum, nose, gut, uterus and prostate with the immune system. Although considered part of a system, each mucosa presents specific immune features beyond the barrier and secretory functions. Information regarding the mucosal immunology of the male reproductive tract and the prostate gland in particular is scarce. In this review, we approach the prostate as an epithelial barrier and as part of the mucosal immune system. Finally, we also raise a series of questions that will improve the understanding of this gland, its role in reproduction and its sensitivity/resistance to disease.

From Ancient to Emerging Infections: The Odyssey of Viruses in the Male Genital Tract

The male genital tract (MGT) is the target of a number of viral infections that can have deleterious consequences at the individual, offspring, and population levels. These consequences include infertility, cancers of male organs, transmission to the embryo/fetal development abnormalities, and sexual dissemination of major viral pathogens such as human immunodeficiency virus (HIV) and hepatitis B virus. Lately, two emerging viruses, Zika and Ebola, have additionally revealed that the human MGT can constitute a reservoir for viruses cleared from peripheral circulation by the immune system, leading to their sexual transmission by cured men. This represents a concern for future epidemics and further underlines the need for a better understanding of the interplay between viruses and the MGT. We review here how viruses, from ancient viruses that integrated the germline during evolution through old viruses (e.g., papillomaviruses originating from Neanderthals) and more modern sexually transmitted infections (e.g., simian zoonotic HIV) to emerging viruses (e.g., Ebola and Zika) take advantage of genital tract colonization for horizontal dissemination, viral persistence, vertical transmission, and endogenization. The MGT immune responses to viruses and the impact of these infections are discussed. We summarize the latest data regarding the sources of viruses in semen and the complex role of this body fluid in sexual transmission. Finally, we introduce key animal findings that are relevant for our understanding of viral infection and persistence in the human MGT and suggest future research directions.

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.

Tribbles role in reproduction

Tribbles (TRIB) proteins, a family of evolutionary conserved psuedokinase proteins, modulate various signalling pathways within the cell. The regulatory roles of TRIB make them an important part of a number of biological processes ranging from cell proliferation to metabolism, immunity, inflammation and carcinogenesis. Innate immune system plays a pivotal role during the regulation of reproductive processes that allows successful creation of an offspring. Its involvement initiates from fertilization of the oocyte by spermatozoon and lasts throughout early embryonic development, pregnancy and labour. Therefore, there is a close cooperation between the reproductive system and the innate immune system. Evidence from our lab has demonstrated that improper activation of the innate immune system can reduce embryo implantation, thus leading to infertility. Therefore, control mechanisms regulating the innate immune system function can be critical for successful reproductive events.

Male infertility: a public health issue caused by sexually transmitted pathogens

Sexually transmitted diseases (STDs) are caused by several pathogens, including bacteria, viruses and protozoa, and can induce male infertility through multiple pathophysiological mechanisms. Additionally, horizontal transmission of STD pathogens to sexual partners or vertical transmission to fetuses and neonates is possible. Chlamydia trachomatis, Ureaplasma spp., human papillomavirus, hepatitis B and hepatitis C viruses, HIV-1 and human cytomegalovirus have all been detected in semen from symptomatic and asymptomatic men with testicular, accessory gland and urethral infections. These pathogens are associated with poor sperm quality and decreased sperm concentration and motility. However, the effects of these STD agents on semen quality are unclear, as are the effects of herpes simplex virus type 1 and type 2, Neisseria gonorrhoeae, Mycoplasma spp., Treponema pallidum and Trichomonas vaginalis, because few studies have evaluated the influence of these pathogens on male infertility. Chronic or inadequately treated infections seem to be more relevant to infertility than acute infections are, although in many cases the exact aetiological agents remain unknown.

Chlamydia trachomatis infection increases the expression of inflammatory tumorigenic cytokines and chemokines as well as components of the Toll-like receptor and NF-κB pathways in human prostate epithelial cells

Inflammation has been reported to play a major role in prostate carcinogenesis. Several bacterial infections can lead to prostate inflammation; however, until now, the precise molecular and cellular mechanisms linking inflammation to carcinogenesis have remained unclear. We therefore investigated the initiation of inflammation induced by Chlamydia trachomatis (C. trachomatis) infection in human prostate epithelial cells using an in vitro culture system in which human androgen-independent PC-3 prostate cancer epithelial cells were infected with C. trachomatis serovar L2. The expression levels of VEGF, ICAM-1, IL-6, IL-8, IL-1β, TNFα, CCL5, CCL2 and iNOS inflammation-related genes, as well as genes involved in the Toll-like receptor (TLR) pathway (TLR2, TLR4, CD14 and MyD88), were evaluated at the mRNA level in infected PC-3 cells 24 h after infection with C. trachomatis serovar L2. The expression levels of components of the NF-κB pathway (p65 and IκBα) were evaluated at the mRNA level in infected PC-3 cells at different time points (1, 6, 12 and 24 h) after infection. The expression levels of inflammation-related genes, components of the Toll-like receptor pathway and genes involved in NF-κB activation were analyzed in infected and uninfected cells using semi-quantitative RT-PCR. We detected a significant increase (p < 0.001) in inflammation-related cytokines in infected PC-3 cells. During infection, PC-3 cells elicited a proinflammatory response, as shown by NF-κB activation, TLR2 and TLR4 upregulation and the increased expression of inflammation-related genes. Furthermore, we observed significant upregulation of the adhesion molecules ICAM-1 and VEGF, which are two biomarkers correlated with tumor progression and immune system evasion. The present study suggests that human prostate cancer epithelial cells are susceptible to C. trachomatis infection and upregulate proinflammatory markers during infection.

Sperm protection in the male reproductive tract by Toll-like receptors

Sperm function can be affected by infection. Our understanding of innate immune system molecular mechanisms has been expanded, by the discovery of 'Toll-like receptors' (TLRs). It seems that these receptors could play a critical role in the protection of spermatozoa. This study seeks to examine the presence and distribution of TLRs in different parts of the human male reproductive tract and spermatozoa. So, TLR gene expression was examined by RT-PCR. Quantitative real-time PCR (Q-PCR) analysis used to compare the expression of TLRs in all sections of the male reproductive tract and TLRs 2, 3 and 4 in testicular sperm extraction (TESE) samples, which contained spermatozoa (TESE+) and those that did not (TESE-). Results showed that all TLR genes were expressed in different parts of the human male reproductive tract and spermatozoa. Moreover, Q-PCR indicated that the relative expression of TLRs did not significantly change in different parts of the male reproductive tract but this technique has shown only relative TLR2 expression in TESE- is lower than TESE+ samples. It could be concluded that TLRs may provide a broad spectrum of protection from infection in the male reproductive tract. Furthermore, TLRs may influence on the developmental process during spermatogenesis.

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.

Prostate cancer and inflammation: the evidence

Chronic inflammation is now known to contribute to several forms of human cancer, with an estimated 20% of adult cancers attributable to chronic inflammatory conditions caused by infectious agents, chronic non-infectious inflammatory diseases and/or other environmental factors. Indeed, chronic inflammation is now regarded as an 'enabling characteristic' of human cancer. The aim of this review is to summarize the current literature on the evidence for a role for chronic inflammation in prostate cancer aetiology, with a specific focus on recent advances regarding the following: (i) potential stimuli for prostatic inflammation; (ii) prostate cancer immunobiology; (iii) inflammatory pathways and cytokines in prostate cancer risk and development; (iv) proliferative inflammatory atrophy (PIA) as a risk factor lesion to prostate cancer development; and (v) the role of nutritional or other anti-inflammatory compounds in reducing prostate cancer risk.

Chemokine response induced by Chlamydia trachomatis in prostate derived CD45+ and CD45- cells

The role of innate cells and their receptors within the male genital tract remains poorly understood. Much less is known about the relative contribution of different genital tract cells such as epithelial/stromal cells and resident leucocytes. In this study, we examined innate immune responses to Chlamydia trachomatis by prostate epithelial/stromal cells and prostate resident leucocytes. Murine prostate primary cultures were performed and leucocyte and epithelial/stromal cells were sorted based on surface protein expression of CD45 by magnetism-activated cell sorting or fluorescence-activated cell sorting. Prostate derived CD45- and CD45+ cells were infected with C. trachomatis and chemokine secretion assayed by ELISA. Similar experiments were performed using prostate CD45+ and CD45- cells from myeloid differentiation factor 88 (Myd88(-/-)) mice or toll-like receptor (Tlr2(-/-)) and Tlr4(mutant) double-deficient mice. Moreover, a TLR-signalling pathway array was used to screen changes in different genes involved in TLR-signalling pathways by real-time PCR. Prostate derived CD45- and CD45+ cells responded to chlamydial infection with the production of different chemokines. Both populations expressed genes involved in TLR signalling and required to respond to pathogen-associated molecular patterns and to C. trachomatis infection. Both populations required the adaptor molecule MYD88 to elicit chemokine response against C. trachomatis. TLR2-TLR4 was essential for chemokine production by CD45+ prostate derived cells, but in their absence, CD45- cells still produced significant levels of chemokines. We demonstrate that C. trachomatis is differentially recognised by prostate derived CD45+ and CD45- cells and suggest that diverse strategies are taking place in the local microenvironment of the host in response to the infection.