Interleukin-1 system in testis — quantitative analysis

Regulation of Human Spermatogenesis

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].

Effects of short- and long-term regular exercise on reproductive tissue in streptozotocin-induced diabetic male Wistar rats

OBJECTIVE

Reproductive disorders are one of the complications of diabetes mellitus. Since conflicting results have been obtained from different studies, which examined serum levels of cytokines in patients with diabetes, and considering the fact that the origin of cytokines cannot be accurately determined from their serum changes, attempts were made in the present study to study histological changes and testicular tissue levels of TNF-α and IL-1 in rats treated with exercise. Considering the effects of exercise in reducing blood sugar level and its complications, two types of short-term and long-term regular exercises were also considered to evaluate their effects on male reproductive tissues.

METHODS

In this study, 60 male rats with the weight range of 250±50 g were used and were randomly divided into six groups (10 rats each). Healthy groups included sedentary control group, and groups treated with two and eight weeks of exercise. Rats with type 1 diabetes (induced by streptozotocin) included sedentary control group, groups treated with two and eight weeks of exercise (six groups). All groups were evaluated in terms of testicular tissue levels of TNF-α and IL-1 using ELISA and the histometry of spermatogonia, primary spermatocytes, Sertoli cells, epithelial thickness, diameter of veins, and thickness of the seminiferous tubule.

RESULTS

Histological changes resulting from diabetes, particularly in the diameter of testicular veins and a number of cells, including Sertoli, highlights the important fact that tissue perfusion in patients with diabetes is especially crucial, in a way that exercise proved useful for tissue structures by offsetting this complication. Measurement of the cytokines IL-1 and TNF-α in the current study showed that perfusion problems are more important in diabetic complications than inflammatory factors.

CONCLUSIONS

The main result of this research is recommendation of investigating the tissue of interest for diagnosis of diabetes complications, measuring inflammatory mediators of tissue rather than evaluating their serum concentrations, and focusing on vascular complications as a major complication of diabetes. Furthermore, regular exercise could help improve the function of reproductive organs in healthy groups and prevent diabetes infertility complications to an acceptable degree in diabetic groups.

Intratesticular expression of mRNAs of both interferon γ and tumor necrosis factor α is significantly increased in experimental autoimmune orchitis in mice

Experimental autoimmune orchitis (EAO) is one of the models of immunological male infertility. Murine EAO is CD4+T cell-dependent and classically induced by immunization with a testicular homogenate and adjuvants. We previously established that immunization with viable syngeneic testicular germ cells (TGC) can also induce murine EAO with no use of any adjuvant. Analyses of this EAO model have already revealed that cultured spleen cells of immunized mice secreted interferon (IFN)-γ and that treatment of the immunized mice with anti-IFN-γ monoclonal antibodies significantly suppressed the EAO. It is known that both IFN-γ and tumor necrosis factor (TNF)-α are representative cytokines of Th1 cells and exhibit local toxicity toward the seminiferous epithelium in vivo. However, changes in these two cytokines in EAO-affected testes have not yet been investigated. Therefore, in the present study, we investigated the expression of intratesticular IFN-γ and TNF- α mRNAs in TGC-induced EAO using real-time RT-PCR. The results demonstrated that the intratesticular mRNAs for both IFN-γ and TNF-α significantly increased, while other cytokines such as IL-1α, IL-1β, IL-6 and TGF-β did not show dramatic changes in the immunized mice. These results suggest that secretion of significant amounts of IFN-γ and TNF-α in situ contributes to the spermatogenic disturbance in EAO.

Inflammatory networks in the control of spermatogenesis : chronic inflammation in an immunologically privileged tissue?

Spermatogenesis is a complex, organized process involving intimate interactions between the developing germ cells and supporting Sertoli cells. The process is also highly regulated. Studies suggest that regulation in the seminiferous epithelium involves molecules normally associated with either immune or inflammatory processes; in particular, interleukin 1a (IL1a), IL6, tumor necrosis factor (TNFa), activin A and nitric oxide (NO). While there is considerable evidence that these inflammatory mediators have effects on spermatogonial and spermatocyte development as well as critical supportive functions of the Sertoli cells, which are undoubtedly of considerable importance during testicular inflammation, there remains some skepticism regarding the significance of these molecules with respect to normal testicular function. Nonetheless, it is evident that expression of these regulators varies across the cycle of the seminiferous epithelium in a consistent manner, with major changes in production coinciding with key events within the cycle. This review summarizes the evidence supporting the hypothesis that inflammatory cytokines play a role in normal testicular spermatogenesis, as well as in the etiology of inflammation induced sub-fertility. The balance of data leads to the striking conclusion that the cycle of the seminiferous epithelium resembles a chronic inflammatory event. This appears to be a somewhat paradoxical assertion, since the testis is an immunologically privileged tissue based on its well-established ability to support grafts with minimal rejection responses. However, it may be argued that local immunoregulatory mechanisms, which confer protection from immunity on both transplanted tissues and the developing spermatogenic cells, are equally necessary to prevent local inflammation responses associated with the spermatogenic process from activating the adaptive immune response.

Identification of IL-18RAP mRNA truncated splice variants in human testis and the other human tissues

IL-18 is a pleiotropic cytokine involved in the regulation of both innate and adaptive immunity. It plays a key role in the autoimmune, inflammatory and infectious diseases. IL-18 acts via a receptor complex that closely resembles that of IL-1, consisting of a ligand binding protein, IL-18Ralpha, and an accessory protein, IL-18RAP (IL-18Rbeta). IL-18RAP is essential for IL-18 signal transduction and ligand binding affinity to IL-18Ralpha receptor chain. mRNA of gene coding for IL-18RAP in human testicular tissue and the nucleotide sequence of splice variants was carefully examined. We have found for the first time ever, IL-18RAP mRNA in studied tissue samples of physiological testis. Using the RT-PCR technique, the whole coding sequence of this gene was amplified. An alternative splicing of mRNA for IL-18RAP was then discovered and subsequently confirmed by cDNA sequencing. The putative amino acid content was predicted and a computer modeling was performed. It might be hypothesized that the truncated forms of IL-18RAP can be involved in the complex mechanism of IL-18 activity regulation.

Interleukin-1 superfamily genes expression in normal or impaired human spermatogenesis

Interleukin-1 (IL-1) is a pleiotropic cytokine that may play a role in contributing to the specific immune environment of mammalian testis and in regulating cell differentiation. We have determined the transcription activity of the IL-1 gene family (using real-time polymerase chain reaction (PCR)) in two main functional testicular compartments (interstitial and intratubular ones), and in tissue homogenates obtained from patients with fertility disorders (spermatogenic arrest and testicular tumors). We observed the prominent expression of gene coding for IL-1 receptor antagonist (IL-1RA) in a purified fraction of gametogenic cells (normal gonad). Caspase-1 (ICE - IL-1beta-converting enzyme) was highly expressed (on mRNA level) in interstitial compartments as well in testicular tumors (immune enhancement?). In addition we found, that the activity of IL-1RA gene decreased along spermatogenic alteration in an inversely related manner with IL-1alpha (from normal gonad through spermatogenic arrest to Sertoli cell only syndrome). Therefore, the quotient value of IL-1alpha/IL-1RA could potentially serve as the diagnostic molecular probe for spermatogenesis assessment. The precise level of mRNA for IL-1-IL-18 cytokines and their receptors, and specifically of the receptor antagonist in immune privileged gonad, could be one of the main factors responsible for maintaining testicular homeostasis, thus enabling generation of the mature spermatozoa.

Cytokine profiles in the testes of rats treated with lipopolysaccharide reveal localized suppression of inflammatory responses

Evidence indicates that the testis possesses a reduced capacity to mount inflammatory and rejection responses, which undoubtedly contributes to the ongoing survival of the highly immunogenic germ cells. The contribution of local cytokine expression to this condition was investigated in adult male rats treated with lipopolysaccharide to induce inflammation. Cytokine mRNA and protein expression were determined in tissue extracts and fluids by Northern blot analysis, quantitative PCR, or RNAse protection assay and specific ELISAs. Testicular expression of the proinflammatory cytokines, interleukin (IL)-1β and tumor necrosis factor-α was considerably attenuated compared with the liver (control tissue); in contrast, the testicular IL-6 response was enhanced. Expression of IL-10, a type 2 immunoregulatory cytokine, was similar in both testis and liver, whereas the immunoregulatory/anti-inflammatory cytokines transforming growth factor-β1and activin A were constitutively elevated in both normal and inflamed testes. The IL-1β and transforming growth factor-β1proteins were present principally in their latent (inactive) forms, indicating that enzymic processing is an important control mechanism for these two cytokines within the testis. These data indicate that inflammatory and regulatory cytokine activity is regulated at both transcriptional and posttranslational levels in a testis-specific manner. It is concluded that a novel pattern of suppression of proinflammatory cytokine responses and normal or elevated expression of immunoregulatory cytokines may be responsible for reduced inflammatory responses and enhanced graft survival in the testis. These data have important implications for the understanding and treatment of male autoimmune infertility, testicular inflammation. and carcinogenesis.

Quantitative mRNA Analysis of IL-1 Gene System in Human Testis

PROBLEM

There is a growing body of evidence that interleukins exhibit modulatory activity on development of reproductive cells. In this context, there appears to be a role for IL-1, which is also produced in human testis. We have analysed transcripts of IL-1 gene system (IL-1alpha, IL-1beta, IL-1RI, IL-1RII and IL-1RA) to evaluate the possible link between the level of gene(s) transcription and their function.

METHOD OF STUDY

To determine the activity of gene transcription, a quantitative PCR with isotopic and/or nonisotopic detection was applied.

RESULTS AND CONCLUSIONS

We have detected differential expression of IL-1alpha and IL-1beta genes in separate functional compartments of a male gonad. A strong expression of IL-1alpha gene in an intratubular cell fraction was shown, while the IL-1beta expression seemed to be dominant in extratubular compartment of the male gonad. Abundant amounts of IL-1RA mRNA in gametogenic cells fraction slightly higher than in interstitium have also been found. IL-1RA is the most important regulatory molecule in IL-1 system, which down-regulates activity of both interleukins. Looking more closely at gene(s) differential expression it appears that IL-1alpha can be preferentially down-regulated by IL-1RA gene in intratubular fraction while the IL-1beta, through the "false" IL-1RII receptor in the interstitium. Genes coding for both receptors (IL-1RI and IL-1RII) showed, however, relatively low levels of transcription in both studied compartments. IL-1 genes system creates a complex intragonadal environment and the function of these genes is reflected by their respective distribution in the two main functional compartments of the testis.