Lipopolysaccharide, latex beads and residual bodies are potent activators of Sertoli cell interleukin-1 alpha production

Crosstalk between reproductive and immune systems: the teleostean perspective

The bidirectional interaction between the hypothalamic-pituitary-gonadal (HPG) axis and the immune system plays a crucial role in the adaptation of an organism to its environment, its survival and the continuance of a species. Nonetheless, very little is known about this interaction among teleost, the largest group of extant vertebrates. Fishes being seasonal breeders, their immune system is exposed to seasonally changing levels of HPG hormones. On the contrary, the presence and infiltration of leukocytes, the expression of pattern recognition receptors as well as cytokines in gonads suggest their key role in teleostean gametogenesis as in the case of mammals. Moreover, the modulation of gametogenesis and steroidogenesis by lipopolysaccharide implicates the pathological significance of inflammation on reproduction. Thus, it is important to engage in the understanding of the interaction between these two important physiological systems, not only from a phylogenetic perspective but also due to the importance of fish as an important economic resource. In view of this, the authors have reviewed the crosstalk between the reproductive and immune systems in teleosts and tried to explore the importance of this interaction in their survival and reproductive fitness.

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].

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.

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.

Activation of innate immune system in response to lipopolysaccharide in chicken Sertoli cells

Sertoli cells (SCs) play an important physiological role in the testis, as they support, nourish, and protect the germ cells. As protection of the developing spermatozoa is an emerging aspect of reproductive physiology, this study examined the expression pattern of innate immune-related genes, including avian β-defensins (AvBDs), Toll-like receptors (TLRs), and cytokines, and investigated the time course of an inflammatory response in rooster SCs triggered by exposure to the bacterial endotoxin lipopolysaccharide (LPS). SCs were isolated from 6-week-old chicken, culturedin vitro, and stimulated with 1 μg/ml LPS at different time courses (0, 6, 12, 24, and 48 h). Data on expression analysis revealed that all ten members of the chickenTLRfamily, nine members of theAvBDfamily, as well as eight cytokine genes were expressed in SCs. Quantitative real-time PCR analysis revealed that LPS treatment resulted in significant induction of the expression levels of sixTLRs, sixAvBDs, and four cytokine genes, while two cytokine genes were downregulated and two other genes were unchanged. The increasing interleukin 1β (IL1β) production was confirmed in the conditioned medium. Furthermore, the phagocytosis of SCs was increased after LPS treatment. In conclusion, these findings provide evidence that SCs express innate immune-related genes and respond directly to bacterial ligands. These genes represent an important component of the immune system, which could be integrated into semen, and present a distinctive constituent of the protective repertoire of the testis against ascending infections.

Regulation of actin dynamics and protein trafficking during spermatogenesis--insights into a complex process

In the mammalian testis, extensive restructuring takes place across the seminiferous epithelium at the Sertoli-Sertoli and Sertoli-germ cell interface during the epithelial cycle of spermatogenesis, which is important to facilitate changes in the cell shape and morphology of developing germ cells. However, precise communications also take place at the cell junctions to coordinate the discrete events pertinent to spermatogenesis, namely spermatogonial renewal via mitosis, cell cycle progression and meiosis, spermiogenesis and spermiation. It is obvious that these cellular events are intimately related to the underlying actin-based cytoskeleton which is being used by different cell junctions for their attachment. However, little is known on the biology and regulation of this cytoskeleton, in particular its possible involvement in endocytic vesicle-mediated trafficking during spermatogenesis, which in turn affects cell adhesive function and communication at the cell-cell interface. Studies in other epithelia in recent years have shed insightful information on the intimate involvement of actin dynamics and protein trafficking in regulating cell adhesion and communications. The goal of this critical review is to provide an updated assessment of the latest findings in the field on how these complex processes are being regulated during spermatogenesis. We also provide a working model based on the latest findings in the field including our laboratory to provide our thoughts on an apparent complicated subject, which also serves as the framework for investigators in the field. It is obvious that this model will be rapidly updated when more data are available in future years.

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.

The biology of interleukin-1: emerging concepts in the regulation of the actin cytoskeleton and cell junction dynamics

Interleukin (IL)-1 is a proinflammatory cytokine with important roles in innate immunity, as well as in normal tissue homeostasis. Interestingly, recent studies have also shown IL-1 to function in the dynamics of the actin cytoskeleton and cell junctions. For example, treatment of different epithelia with IL-1α often results in the restructuring of the actin network and cell junctions, thereby leading to junction disassembly. In this review, we highlight new and interesting findings that show IL-1 to be a critical player of restructuring events in the seminiferous epithelium of the testis during spermatogenesis.

Regulation of Sertoli cell activin A and inhibin B by tumour necrosis factor α and interleukin 1α: interaction with follicle-stimulating hormone/adenosine 3',5'-cyclic phosphate signalling

Regulation of crucial events during spermatogenesis involves dynamic changes in cytokine production and interactions across the cycle of the seminiferous epithelium. Regulation of activin A and inhibin B production by the inflammatory cytokines, tumour necrosis factor α (TNFα) and interleukin 1α (IL1α), alone and in conjunction with FSH or a cAMP analogue (dibutyryl cAMP), was examined in cultures of Sertoli cells from 20-day old rats. Both TNFα and IL1α stimulated activin A secretion and expression of its subunit (β(A)) mRNA, and suppressed inhibin B secretion and expression of its subunit (α and β(B)) mRNAs. The actions of TNFα and IL1α were opposed by FSH and dibutyryl cAMP. Both cytokines inhibited FSH/dibutyryl cAMP-stimulated inhibin B secretion and mRNA expression as well as stem cell factor mRNA expression. Both cytokines also inhibited FSH-induced cAMP production, and reduced baseline FSH receptor mRNA expression. These data highlight the reciprocal relationship that exists between FSH/cAMP signalling and inflammatory cytokine signalling pathways in the control of Sertoli cell function, and production of activin A/inhibin B in particular. It is anticipated that these interactions play important roles in the fine control of events during the cycle of the seminiferous epithelium and in the inhibition of spermatogenesis during inflammation.

Toll-like receptors and signalling in spermatogenesis and testicular responses to inflammation--a perspective

It is self-evident that infection and inflammation in the reproductive tract can inhibit male fertility, but the observation that fertility may also be compromised by systemic inflammation and disease is more difficult to explain. Recent studies implicating microbial pattern-recognition receptors, such as the Toll-like receptors (TLRs), as well as inflammatory cytokines and their signalling pathways, in testicular function have cast new light on this mysterious link between infection/inflammation and testicular dysfunction. It is increasingly evident that signalling pathways normally involved in controlling inflammation play fundamental roles in regulating Sertoli cell activity and responses to reproductive hormones, in addition to promoting immune responses within the testis. Many of the negative effects of inflammation on spermatogenesis may be attributed to elevated production of inflammation-related gene products within the circulation and the testis, which subsequently exert disruptive effects on spermatogenic cell development and survival, as well as the ability of the Sertoli cells to provide support for spermatogenesis. These interactions have important implications for testicular dysfunction and disease, and may eventually provide new opportunities for therapeutic interventions.

Immunology of the Testis and Male Reproductive Tract

A large body of evidence points to the existence of a close, dynamic relationship between the immune system and the male reproductive tract, which has important implications for our understanding of both systems. The testis and the male reproductive tract provide an environment that protects the otherwise highly immunogenic spermatogenic cells and sperm from immunological attack. At the same time, secretions of the testis, including androgens, influence the development and mature functions of the immune system. Activation of the immune system has negative effects on both androgen and sperm production, so that systemic or local infection and inflammation compromise male fertility. The mechanisms underlying these interactions have begun to receive the attention from reproductive biologists and immunologists that they deserve, but many crucial details remain to be uncovered. A complete picture of male reproductive tract function and its response to toxic agents is contingent upon continued exploration of these interactions and the mechanisms involved.

Differential responses of epithelial Sertoli cells of the rat testis to Toll-like receptor 2 and 4 ligands: Implications for studies of testicular inflammation using bacterial lipopolysaccharides

The relative contribution of epithelial Sertoli cells in response to bacterial infection of the testis remains poorly characterised, since studies on inflammatory properties of these cells have invariably used unpurified lipopolysaccharide (LPS) preparations contaminated with bacterial lipopeptides. Consequently, isolated rat Sertoli cells were stimulated with either unextracted or phenol re-extracted LPS, and analysed for Toll-like receptor (TLR) 4, TLR2 and inflammatory cytokine gene expression by quantitative reverse transcription polymerase chain reaction (RT-PCR). Expression of TLR4 and its co-receptor protein myeloid differentiation (MD) 2 in Sertoli cells and testicular macrophages were similar, but Sertoli cells displayed low basal or LPS-induced expression of the TLR4 accessory protein, CD14. In Sertoli cells, unextracted LPS produced cytokine responses which were considerably greater in magnitude and duration compared with their response to purified LPS. Sertoli cells also responded to the synthetic lipopeptide, Pam3Cys (a TLR2 ligand) with a similar pattern of prolonged gene expression. Sertoli cells were more than 10-fold less sensitive to purified LPS than macrophages, but expressed similar levels of interleukin (IL)-1α and IL-6, and much greater levels of the immunoregulatory cytokine activin A, when maximally stimulated. These data demonstrate that Sertoli cells display differential cytokine responses to bacterial stimuli, mediated by both TLR2 and TLR4, that are distinct from those of testicular macrophages.

Regulation of interleukin 1alpha, activin and inhibin by lipopolysaccharide in Sertoli cells from prepubertal rats

Bacterial lipopolysaccharide increased the production of interleukin 1alpha and activin A, and reduced production of inhibin B, in Sertoli cells from immature male rats measured by enzyme-linked immunosorbent assay (ELISA). The majority of immunoreactive interleukin 1alpha remained within the Sertoli cell, while both activin A and inhibin B were secreted. Lipopolysaccharide-stimulated expression of two interleukin 1alpha mRNA transcripts, measured by quantitative RT-PCR, but the levels of bioactive interleukin 1alpha in Sertoli cell extracts and medium, measured by in vitro bioassay, were comparatively low to undetectable. A specific antagonist of interleukin 1alpha had no effect on lipopolysaccharide-stimulated activin A or inhibin B responses. These data indicate that, in contrast to Sertoli cells from adult rats, lipopolysaccharide-induced regulation of activin A and inhibin B by prepubertal Sertoli cells does not involve secreted interleukin 1alpha. The data highlight the possibility of a role for intracellular interleukin 1alpha in the Sertoli cell response to inflammation, particularly in the immature testis.

Post-natal changes in testicular concentrations of interleukin-1 alpha and beta and interleukin-6 during sexual maturation in bulls

Based on observations in laboratory animals interleukins could be regulators of testicular development. The objects of this study were to see if interleukins (IL-1 and IL-6) are present in the developing bull testis and to establish the temporal patterns of concentrations of IL-1 and IL-6 in the bovine testis during development. Separate groups of six bull calves were castrated every 4 weeks from 5 to 33 weeks of age, and at 56 weeks of age. Mean testicular IL-1 alpha concentrations decreased (p < 0.01) from 5 to 9 weeks of age and 13 to 21 weeks of age. Mean testicular IL-1 beta concentrations decreased (p < 0.01) from 13 to 17 weeks of age and from 29 to 33 weeks of age. Mean IL-1 bioactivity increased from 13 to 17 weeks of age, decreased to 21 weeks, increased to 25 weeks, decreased to 29 weeks and decreased from 33 to 56 weeks of age (p < 0.05). Mean testicular IL-6 concentrations decreased (p < 0.05) from 9 to 13 weeks of age, increased (p < 0.05) to 21 weeks, decreased (p < 0.05) to 25 weeks, increased (p < 0.05) to 29 weeks and decreased (p < 0.01) to 56 weeks of age. In conclusion, testicular IL-1 alpha, IL-1 beta and IL-6 were found in the bovine testis and concentrations were age dependent. Testicular IL-1 alpha and IL-1 beta concentrations were highest in the early post-natal period; however, IL-1 bioactivity and IL-6 concentrations were greatest in the immediate pre-pubertal period. These findings suggest a functional role for interleukins in testicular development in the bull.

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.

Toll‐like receptors in the gonads and reproductive tract: emerging roles in reproductive physiology and pathology

Interactions between the immune system and reproductive system have important consequences for fertility and reproductive health in general. There is increasing evidence that many of the interactions between the immune and reproductive systems involve the Toll-like receptors (TLRs). While there is no doubt that TLRs are important in providing protection against infection in the reproductive tract, there is increasing evidence for the involvement of TLRs in more basic pathology and physiology of reproduction. In the female, TLRs have been implicated in critical aspects of ovarian, endometrial and placental function, as well as in ovarian cancer, pelvic inflammatory disease, intrauterine growth restriction, pre-eclampsia and preterm birth. In the male, TLRs appear to play a role in the control of testicular steroidogenesis and spermatogenesis in disease and, potentially, during normal function, as well. Recent studies also have begun to highlight the role of various TLRs in the aetiology of prostatitis and prostatic cancer. Given the nascent state of knowledge concerning this important area, it is clear that more studies are needed, which should provide valuable new insights into the biology of the TLRs and reproductive function in general.

Innervation and serotoninergic receptors of the testis interact with local action of interleukin-1beta on steroidogenesis

Testosterone secretion by Leydig cells is affected by interleukin-1beta (IL-1beta). The aim of the present study was to investigate whether partial denervation of the testis or local administration of a serotonin (5-HT) receptor antagonist could alter the changes in testicular steoidogenesis induced by IL-1beta. Intratesticular administration of IL-1beta was combined with vasectomy or local injection of ketanserin (5-HT type 2 receptor antagonist) in immature hemicastrated rats and the effect of the interventions on testicular steroidogenesis was studied. One day after treatment with local injection of IL-1beta induced a significant rise in testosterone secretion that could be prevented by vasectomy (that also means transection of the inferior spermatic nerve). In a model in which neither IL-1beta nor ketanserin interfered with steroidogenesis, administration of the receptor antagonist just prior to IL-1beta treatment significantly reduced testosterone secretion. Data indicate interaction between testicular nerves and IL-1beta action and interaction between testicular 5-HT2 receptors and local effect of IL-1beta on testosterone secretion.

A multistep kinase-based sertoli cell autocrine-amplifying loop regulates prostaglandins, their receptors, and cytokines

In Sertoli epithelial cells, the IL-1beta induces prostaglandins (PG) PGE(2), PGF(2alpha) and PGI(2) (7-, 11-, and 2-fold, respectively), but not PGD(2), production. Cyclohexamide pretreatment inhibiting protein synthesis prevents IL-1beta increases in PG levels, indicating that induction requires de novo protein synthesis. IL-1beta-regulated PGE(2) and PGF(2alpha) production and cytokine expression require activation of cyclooxygenase-2 (COX-2) and c-Jun NH(2)-terminal kinase, as shown using specific enzyme inhibition. PGE(2) and PGF(2alpha) stimulate expression of IL-1alpha, -1beta, and -6, findings consistent with PG involvement in IL signaling within the seminiferous tubule. PGE(2) and PGF(2alpha) reverse COX-2-mediated inhibition of IL-1beta induction of cytokine expression and PG production. Sertoli PG receptor expression was determined; four known E-prostanoid receptor (EP) subtypes (1-4) and the F-prostanoid and prostacyclin prostanoid receptors were demonstrated using RNA and protein analyses. Pharmacological characterization of Sertoli PG receptors associated with cytokine regulation was ascertained by quantitative real-time RT-PCR analyses. IL-1beta regulates both EP(2) mRNA and protein levels, data consistent with a regulatory feedback loop. Butaprost (EP(2) agonist) and 11-deoxy PGE(1) (EP(2) and EP(4) agonist) treatments show that EP(2) receptor activation stimulates Sertoli cytokine expression. Consistent with EP(2)-cAMP signaling, protein kinase A inhibition blocks both IL-1beta- and PGE(2)-induced cytokines. Together, the data indicate an autocrine-amplifying loop involving IL-1beta-regulated Sertoli function mediated by COX-2-induced PGE(2) and PGF(2alpha) production. PGE(2) activates EP(2) and/or EP(4) receptor(s) and the protein kinase A-cAMP pathway; PGF(2alpha) activates F-prostanoid receptor-protein kinase C signaling. Further identification of the molecular mechanisms subserving these mediators may offer new insights into physiological events as well as proinflammatory-mediated pathogenesis in the testis.

Increased expression of interleukin-1α and interleukin-1β is associated with experimental varicocele

OBJECTIVE

To describe the effect of varicocele, in an experimental rat model, on the levels of IL-1alpha and IL-1beta proteins in testis tissue.

DESIGN

Comparative and controlled study.

SETTING

Experimental research.

ANIMAL(S)

Wistar male rats in experimental and control groups.

INTERVENTION(S)

The control group underwent sham operation (n = 6). Experimental groups underwent partial ligation of the renal vein to induce experimental varicocele and were then killed at 9 (n = 6), 11 (n = 6), and 13 (n = 6) weeks after induction of varicocele.

MAIN OUTCOME MEASURE(S)

Histologic evaluation of the varicocele model was determined by periodic acid-Schiff staining of paraffin-embeded testicular tissues. Levels of cytokines were assessed by immunohistochemistry and Western blot analysis.

RESULT(S)

Varicocele caused testicular damage, especially in 11- and 13-week-old varicocele groups. In sham-operated rats, Golgi complexes of round spermatids expressed especially the alpha form of IL-1. By the progression of varicocele, the IL-1alpha expression increased temporally in Sertoli cells, spermatogonia, primary spermatocytes, spermatids, and Leydig cells. The expression of IL-1beta was seen in Leydig cells in sham-operated rats. The IL-1beta expression was also increased upon progression of varicocele in Leydig cells, Sertoli cells, and spermatogonia.

CONCLUSION(S)

We suggest that IL-1alpha and IL-1beta are the regulators of testicular function. Certain pathologic conditions, e.g., varicocele, cause an increase in the expressions of such proinflammatory cytokines. The increased expression of IL-1alpha and IL-1beta in varicocele shifts the balance in favor of inflammatory and immune responses and causes detrimental effects in testis tissue, which may cause male infertility.

Human testis in organotypic culture: application for basic or clinical research

BACKGROUND

Over recent decades, recurring efforts have been devoted to developing testicular cell or tissue cultures for basic and clinical research. However, there remains much confusion, particularly concerning the fate of human germ cells in culture.

OBJECTIVE

To reassess the status of human testicular cell types as well as the ability of germ cells to divide and differentiate in organotypic culture.

METHODS

Human testicular fragments were maintained for 2 weeks in culture. The viability and functionality of testicular cells were assessed using light and electronic microscopy, apoptotic cell labelling, 5-bromo-2'-deoxyuridine (BrdU) incorporation, immunohistochemistry and quantitative PCR against specific cell markers.

RESULTS

A gradual loss of meiotic and post-meiotic germ cells occurred throughout the culture period, irrespective of the presence of gonadotrophins. However, all germ cell types remained traceable for up to 16 days, some still dividing and differentiating at a rate compatible with the in vivo situation. Good maintenance of the general architecture of the explants associated with clearly quantifiable levels of several somatic cell markers was observed.

CONCLUSION

Although this culture model is clearly unsuitable for preparing germ cells for therapeutic purposes, it does represent a most valuable tool for testing the effects of biological and chemical agents on testicular tissue.

Sertoli cell expression of steroidogenic acute regulatory protein-related lipid transfer 1 and 5 domain-containing proteins and sterol regulatory element binding protein-1 are interleukin-1beta regulated by activation of c-Jun N-terminal kinase and cyclooxygenase-2 and cytokine induction

In testicular Sertoli cells, IL-1beta regulates steroid, lactate, and transferrin secretion; although each influences germ cell development and spermatogenesis, little is known about the signaling mechanisms involved. In other cell types, IL-1beta potently induces reactive oxygen species and/or cyclooxygenase-2 (COX-2). In contrast, in Sertoli cells, IL-1beta does not generate reactive oxygen species, but rapidly phosphorylates c-Jun-NH(2)-terminal kinase (JNK), but not p44/42 or p38 MAPK. Phosphorylated JNK stimulates COX-2 activity, mediating the expression of ILs and steroidogenic acute regulatory (StAR)-related (StAR-related lipid transfer protein domain containing) proteins D1 and D5, but not D4. In a time- and dose-dependent manner, IL-1beta rapidly increases levels of COX-2 mRNA (2-fold); induction of COX-2 protein (50-fold) requires de novo protein synthesis. Concomitantly, increases in IL-1alpha, IL-6, and IL-1beta mRNAs (1-3 h) are observed. As StAR-related lipid transfer protein domain containing protein 1 (StARD1) mRNA decreases, StARD5 mRNA increases; substantial recovery phase induction of StARD1 mRNA above control is noted (24 h). Inhibition of JNK or COX-2 activities prevents IL-1beta induction of IL and StARD5 mRNAs and subsequent increases in StARD1 mRNA (24 h), indicating that these effects depend on the activation of both enzymes. StARD1 and D5 protein levels are significantly altered, consistent with posttranscriptional and posttranslational regulation. IL-1beta rapidly decreases levels of precursor and mature sterol regulatory element-binding protein-1, changes not altered by cycloheximide, suggesting coordinate regulation of StARD1 and -D5, but not StARD4, expression. These data demonstrate that JNK and COX-2 activities regulate Sertoli cytokines and particularly START domain-containing proteins, suggesting protective stress responses, including transcription and protein and lipid regulation, within this specialized epithelium.

Interleukin 1-beta injected into the testis acutely stimulates and later attenuates testicular steroidogenesis of the immature rat

The effect of intratesticular administration of interleukin-1beta (IL-1beta) on steroidogenesis was studied in immature and adult rats. In 21-d-old animals local bilateral injection or unilateral administration of 0.1 microg/testis of IL-1beta to hemicastrates resulted in a significant increase in basal testosterone secretion in vitro and serum testosterone concentration one day posttreatment. Six days after treatment the cytokine induced opposite effect in animals with two testes in situ, i.e., it suppressed steroidogenesis. When IL-1beta was combined with hemi-castration, IL-1beta failed to alter the parameters studied. In adult animals subjected to bilateral treatment or to unilateral injection followed by hemicastration, IL-1beta in doses of 1.5 microg/testis or 15 microg/testis did not influence steroidogenesis and serum testosterone concentration. No change in serum LH and FSH concentration could be observed in any experimental group. The data suggest that the proinflammatory cytokine IL-1beta exerts a local action on testicular steroidogenesis, and the effect is age-dependent.

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.

Ultrastructure of testicular macrophages in aging mice

Testicular macrophages of aging mice were studied by TEM. Testicular macrophages retained with Leydig cells the close morphological relationships observed in the adult young animals, but digitations were not found. Lipofuscin granules like those of the Leydig cells from aging mice were observed in the cytoplasm. These organelles were generally absent in the testicular macrophages of young adult mice. Testicular macrophages did not display phagocytosis of the lipofuscin granules. In addition, the latter were not found in the intercellular spaces. These observations indicated that lipofuscin granules were formed, at least in a great part, within testicular macrophages as a consequence of metabolic changes occurring with age. Fine lamellar organization was seen in the lipofuscin granules of both Leydig cells and testicular macrophages. Frequently, lipofuscin granules originated from secondary lysosomes containing lipidic vacuoles only. Together with accumulation of the lipofuscin granules, changes of testicular macrophage fine morphology were observed. Endoplasmic reticulum and Golgi apparatus became poorly developed, and coated vesicles were rarely found. Fewer mitochondria were encountered, but their ultrastructure was not altered. These results suggest that in testicular macrophages lipofuscin accumulation is associated with a functional involution.

Stimulation of steroidogenesis in immature rat Leydig cells evoked by interleukin-1alpha is potentiated by growth hormone and insulin-like growth factors

The cytokine IL-1alpha is produced constitutively by the intact testis, but its function in this organ remains largely unknown. In this study we examined cooperation between IL-1alpha and GH and IGFs with regard to stimulation of steroidogenesis by Leydig cells from 40-d-old rats in vitro. IL-1alpha alone stimulated testosterone (T) and dihydrotestosterone (DHT) production. GH, IGF-I, or IGF-II alone was without effect on T production, but they were found to elevate DHT release, albeit without an obvious dose-response effect. Costimulation with IL-1alpha and GH or with IL-1alpha and IGF-I or IGF-II elevated the rate of steroidogenesis (both T and DHT) above that observed with IL-1alpha alone. GH was found to increase the level of IGF-I in the cultured Leydig cells, an effect that was potentiated by IL-1alpha. The costimulatory effect of GH on steroidogenesis was abolished by treatment with picropodophyllin, a specific inhibitor of the IGF-I receptor, indicating that the action of GH is mediated via IGF-I. Moreover, cells costimulated with IL-1alpha and GH exhibited a marked decrease in the level of intact IGF-binding protein-3 in the culture medium due to the induction of proteolytic activity toward this binding protein. In contrast, secretion of IGF-binding protein-2 was increased by such costimulation. These findings suggest that the stimulation of steroidogenesis in Leydig cells evoked by GH and IGFs requires cooperation with IL-1alpha. This cooperation may play an important role in connection with postnatal Leydig cell maturation and steroidogenesis.

The role of activin, follistatin and inhibin in testicular physiology

The role of the inhibins, activins and follistatins in testicular function are being more clearly defined following studies describing the cellular localisation of these proteins to the testis and the availability of specific assay systems enabling measurement of these proteins. Taken together with the results of targetted gene inactivation experiments, several concepts emerge. Inhibin B is predominantly produced by the Sertoli cell in many adult male mammals whereas there is a perinatal peak of inhibin A in the rat. In contrast, activin A has its highest concentrations in the immediate post-natal period during which it is involved in the developmental regulation of both germ cells and Sertoli cells being modulated by follistatin. Activin A levels are considerably lower in the adult testis but Sertoli cell production is stimulated by interleukin-1 and inhibited by FSH. Little is known about the production of activin B due to the absence of a suitable assay but the beta(B) subunit mRNA is expressed in germ cells and Sertoli cells and is stage-dependent. This pattern of expression suggest that it may be involved in autocrine or paracrine actions within the seminiferous epithelium.

Endotoxin and proinflammatory cytokines modulate Sertoli cell proliferation in vitro

Sertoli cells play a key role in testicular function and their final number in the adult testis determines the capacity of germ cell production. Sertoli cell proliferation, stimulated by FSH and paracrine factors, occurs only in fetal and prepubertal life and may be an important target of pathogenic influences affecting testis development. We used a Sertoli cell proliferation assay to address the question whether if bacterial endotoxin (lipopolysaccharide; LPS) and proinflammatory cytokines could influence early postnatal Sertoli cell development. LPS and tumor necrosis factor-alpha (TNF-alpha) dose-dependently stimulated proliferation of primary cultures of isolated Sertoli cells from 8- to 9-day-old rats, assessed by (3)H-thymidine and BrdU incorporation. LPS also significantly increased the number of living cells in culture, measured by supravital staining. Interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) had no direct effect on Sertoli cell growth, but were found to modulate FSH action. IL-6 increased, while IFN-gamma inhibited, FSH-induced Sertoli cell DNA-synthesis. We conclude that endotoxin and TNF-alpha are potent direct stimulators of Sertoli cell proliferation in vitro, and that IL-6 and IFN-gamma can modulate the mitogenic action of FSH on immature Sertoli cells. This may contribute to the pathogenesis of testicular damage after infections and inflammatory diseases in fetal and early postnatal life, with subsequent disturbance of adult germ cell production.

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.

Cytokines and the immune-testicular axis

Cytokines are regulatory proteins involved in haematopoiesis, immune cell development, inflammation and immune responses. Several cytokines have direct effects on testicular cell functions, and a number of these are produced within the testis even in the absence of inflammation or immune activation events. There is compelling evidence that cytokines, in fact, play an important regulatory role in the development and normal function of the testis. Pro-inflammatory cytokines including interleukin-1 and interleukin-6 have direct effects on spermatogenic cell differentiation and testicular steroidogenesis. Stem cell factor and leukaemia inhibitory factor, cytokines normally involved in haematopoiesis, also play a role in spermatogenesis. Anti-inflammatory cytokines of the transforming growth factor-beta family are implicated in testicular development. Consequently, local or systemic up-regulation of cytokine expression during injury, illness or infection may contribute to the disruption of testicular function and fertility that frequently accompanies these conditions. The aim of this review is to provide a very brief summary of the extensive literature dealing with cytokines in testicular biology, and to follow this with some speculation concerning the significance of these molecules in interactions between the immune system and the testis.

Interleukin-1 is a potent growth factor for immature rat sertoli cells

Testes from rats of different maturational ages were explored for presence of paracrine sertoli cell growth factors. Pubertal and adult testes contained a 17 kDa protein, with potent stimulatory effect on immature Sertoli cell multiplication in vitro. The bioactivity of this protein was mimicked by rat interleukin-1 (IL-1) and neutralized by IL-1 receptor antagonist. A receptor-mediated action was further supported by the demonstration of IL-1 receptor type I mRNA and protein expression in the cultured sertoli cells and in intact immature rat testes. IL-1alpha showed higher efficacy in stimulating proliferation than IL-1beta and follicle-stimulating hormone (FSH), and displayed synergistic action in combination with FSH. As IL-1alpha is constitutively produced by the rat testis and IL-1beta readily inducible by proinflammatory stimuli, our results suggest that IL-1 may serve as a growth factor for Sertoli cells under physiological and pathophysiological conditions.

IL-6 a key cytokine in in vitro and in vivo response of Sertoli cells to external gamma irradiation

Interleukin 1(IL-1) and IL-6 are cytokines involved in the response to radiation and are known for their radioprotective properties with respect to total-body irradiation. We previously showed that after gamma irradiation of Sertoli cells (SC), we observed an increase in the activity of IL-6 but not of IL-1. The aim of this study was to see whether this response is a function of the differentiation of SC, to analyse the mechanisms responsible for this induction, and to test whether this cytokine has a radioprotective role on germ cells. Unlike IL-1, a dose-dependent increase of IL-6 activity in SC following gamma irradiation at high doses was observed at all ages studied. On the other hand, radio-induction observed at low doses (<1Gy) was dose-independent. IL-6 up-regulation resulted from transcriptional activation as shown by the use of specific inhibitors. The injection of IL-1 and IL-6 in mice prior to whole-body irradiation resulted in an increased survival rate. Moreover, cytokines protected DNA from remaining cells following irradiation as shown by comet assay on germ cells. In conclusion, IL-6 seems to constitute a good marker of exposure to gamma irradiation, both at low and high doses. In addition, we showed that IL-1 and IL-6 have a radioprotective effect at testicular level.

Regulation of tissue inhibitor of metalloproteinases-1 in rat Sertoli cells: induction by germ cell residual bodies, interleukin-1alpha, and second messengers

In the testis, FSH has been shown to induce the expression and secretion of tissue inhibitor of metalloproteinases-1 (TIMP-1) from Sertoli cells in vitro. This study was performed to elucidate further the cellular origin of testicular TIMP-1 and its expression by hormonal and paracrine factors. This is the first report on the expression of testicular TIMP-1 in vivo. TIMP-1 mRNA in whole testis was decreased after hypophysectomy and strongly increased by the injection of FSH-S17 to hypophysectomized rats. Primary cultures of both peritubular and Sertoli cells showed basal expression of TIMP-1 mRNA. In contrast, we were unable to detect TIMP-1 mRNA in Leydig cells, freshly isolated immature germ cells (primary spermatocytes and spermatids), or residual bodies. We further show that treatment of Sertoli cells with 8-(4-chlorophenyl)thio-cAMP (8-CPTcAMP) in combination with 12-O-tetradecanoylphorbol 13-acetate (TPA) or Ca(2+) inducers (calcium ionophore A23187 or thapsigargin) had additive (TPA) and synergistic effects (Ca(2+)) on the level of TIMP-1 mRNA and secreted protein. We also show that both the level of TIMP-1 mRNA and secreted protein from Sertoli cells were strongly increased by residual bodies, as well as by the cytokine interleukin-1alpha. TIMP-1 was not up-regulated by either 8-CPTcAMP or interleukin-1alpha in peritubular cells. In contrast to the regulated secretory fraction of TIMP-1, we also detected constitutively expressed immunoreactive TIMP-1 in the nucleus of Sertoli cells, suggesting a role of nuclear TIMP-1 in these cells. In conclusion, our data show that secretion of TIMP-1 from Sertoli cells is highly regulated by hormonal and local processes in the testis, indicating that TIMP-1 is of physiological importance during both testicular development and spermatogenesis.

Role of cytokines in testicular function

Inflammatory disease has been established to affect male reproductive function and fertility. Relevant inflammatory diseases include general and chronic infectious diseases as well as localized acute or chronic infections of the male genitourinary tract. Male accessory gland infections account for almost 15% of all cases of male infertility seen in infertility clinics while fertility usually is not a clinical objective among patients with acute systemic infections such as Gram-negative sepsis. Infections of the male accessory glands frequently are associated with increased counts of white blood cells in semen and elevated levels of proinflammatory cytokines in semen and the testis. There is a mounting body of evidence that demonstrates the importance of cytokines and chemokines in the regulation of testicular and glandular function during pathophysiological states as well as under normal physiological conditions when cytokines act as growth and differentiation factors. The purpose of this review is to examine the role of cytokines in the regulation of steroidogenesis and spermatogenesis in the testis under physiological and pathophysiological conditions and considers clinical investigations that help to improve the evaluation and treatment of male infertility.

Regulation of tissue-type plasminogen activator and its inhibitor (PAI-1) by lipopolysaccharide-induced phagocytosis in a Sertoli cell line

The plasminogen activator (PA) system is thought to play a major role in the proteolytic events associated with spermatogenesis. The mechanisms controlling the expression of PA and of its major physiological inhibitor, plasminogen activator inhibitor type-1 (PAI-1), in the seminiferous epithelium are still unknown. In the present study we analyzed the expression of PA and PAI-1 in a murine Sertoli cell line (42GPA9) in response to stimulation by lipopolysaccharides (LPS) used to activate the phagocytic activity of these cells. Immortalized Sertoli cells cultured under basal conditions secreted predominantly tissue-type PA (tPA) as demonstrated by zymographic analysis and the presence of tPA transcripts. In zymographic experiments a larger molecular weight proteolytic band corresponding to the formation of PA-PAI-1 complex was also observed. The stimulation of immortalized Sertoli cells by LPS resulted in both alteration of the apparent tPA molecular weight to a higher form and transient increase in PAI-1 biosynthesis. The phorbol ester TPA stimulates similarly PAI-1 synthesis in the Sertoli cell line, while 8-bromo-cAMP has no effect. These results suggest for the first time the existence of a direct linkage between molecular events triggered by phagocytosis and regulation of tPA and PAI-1 in Sertoli cells.

Modulation of Leydig cell testosterone production by secretory products of macrophages

Unstimulated macrophages from testes inhibited the production of testosterone by Leydig cells from adult, but not immature, Sprague-Dawley rats (significant after 48 h). Similar results were observed with unstimulated macrophage-conditioned media, suggesting that the observed effect was mediated by one or more secretory products. None of these substances was interleukin-1, since macrophage supernatants tested negative in an interleukin-1 alpha and interleukin-1 beta sensitive, thymocyte assay. Interleukin-6 was detected by a B cell proliferation assay. After stimulation by LPS, testicular macrophages enhanced testosterone production by Leydig cells from adult and immature rats. This enhancement was dose-dependent and required low concentrations (but over 2.5%) of conditioned media. Interleukin-1 and interleukin-6 activities were detected in LPS-stimulated macrophage supernatants. Supernatants of LPS-stimulated, human monocytes had similar effects on Leydig cells. They were rich in interleukin-1, interleukin-1 receptor antagonist and interleukin-6. The present study suggests that, in adult rats, testicular macrophages modulate Leydig cell steroidogenesis by secretory products whose secretion depends on the physiological state of macrophages. The factor or factors responsible for stimulation are not species-specific. The effect cannot be accounted for by variations in the concentration of the above mentioned interleukins in macrophage supernatants.

Residual bodies and IL-1alpha stimulate expression of mRNA for IL-1alpha and IL-1 receptor type I in cultured rat Sertoli cells

The cytokine interleukin (IL)-1alpha may be produced both by Sertoli cells and immature male germ cells from rat and is thought to play a role in autocrine and/or paracrine regulation of the spermatogenesis. The localization of IL-1 receptors in seminiferous tubules is unknown. In this study we found a constitutive expression of IL-1 receptor type I (IL-I RI) mRNA in cultured Sertoli cells and peritubular cells from rat, whereas no such transcripts were observed in immature germ cells (pachytene spermatocytes and round spermatids). An autostimulation of IL-1alpha mRNA synthesis has previously been described in other cell types. Stimulation of Sertoli cells with recombinant IL-1alpha for 0-7 h resulted in a rapid increase in both IL-1alpha and IL-1 RI mRNA. When Sertoli cells were cultured with residual bodies for 0-48 h, mRNA levels for both IL-1alpha and IL-1 RI were increased in a biphasic manner. We suggest that phagocytosis of residual bodies triggers an autocrine IL-1alpha loop in Sertoli cells where both IL-1alpha and one of its receptors are stimulated.

Regulation of Sertoli cell IL-1 and IL-6 production in vitro

Interleukin-1 (IL-1) and IL-6 are pleiotropic cytokines produced by a large variety of cell types. In the testis, Sertoli cells produce IL-1alpha and IL-6. Previous studies have demonstrated that, in vitro, Sertoli cell IL-1alpha production is stimulated by some inducers of macrophage IL-1, as well as by phagocytosis of residual bodies. Furthermore, we have also shown that IL-1alpha is able to enhance Sertoli cell IL-6 production by an autocrine action. The aim of the present study was to further investigate the regulation of Sertoli cell IL-1 and IL-6 production. Three categories of potential regulators were tested; the lipopolysaccharide (LPS) and the yeast extract zymosan; follicle stimulating hormone (FSH), testosterone and dexamethasone; tumor necrosis factor alpha (TNFalpha), interferon gamma (IFNgamma) and the nerve growth factor beta (NGFbeta). It was found that zymosan (400-800 microg/ml) and LPS (20 microg/ml) stimulated Sertoli cell IL-1 and IL-6 production. FSH (1 x 10(-2)-1 microg/ml) and NGF (25-200 ug/ml) stimulated Sertoli cell IL-6 levels in a dose-dependent manner but had no effect on IL-1. The effect of testosterone on Sertoli cell IL-1 and IL-6 secretion was biphasic: dramatic increased secretion with low concentrations (0.01-1 nM) and no effect with the higher concentration tested (100 nM). Dexamethasone reduced LPS-induced IL-1 and IL-6 production in a concentration-responsive manner (0.04-0.4 and 0.4-40 ng/ml, respectively). Addition of TNFalpha to Sertoli cells resulted in a dose-dependent increase of both cytokines (50-100 U/ml for IL-1, 100-200 U/ml for IL-6). In the case of IFNgamma, intermediate concentrations (50-100 U/ml) stimulated IL-1alpha, whereas the highest concentrations (200-400 U/ml) inhibited IL-6. It is concluded that regulation of Sertoli cell IL-1 and IL-6 is very complex as it involves factors as different as hormones, paracrine factors and activators of macrophages. The latter agents may be mimicking the action of pathogens or the action of intratesticular agents whose nature remains to be elucidated.

Vectorial production of interleukin 1 and interleukin 6 by rat Sertoli cells cultured in a dual culture compartment system

The bidirectional production of interleukin-1 (IL-1) and IL-6 by Sertoli cells and its regulation by inflammatory and physiological stimuli has been studied using a dual compartment culture system allowing the study of Sertoli cell apical and basal secretory activities. Another Sertoli cell activity, the vectorial transferrin production was also studied in all culture conditions. A low constitutive IL-1 production appeared equally distributed between both poles, while IL-6 and transferrin constitutive production was predominantly directed apically. Two activators of macrophages, lipopolysaccharides and zymosan, were found to induce marked increases of IL-1 in the compartment where they had been added: basal if added to the lower compartment and vice versa. In contrast, after a basal stimulation, IL-6 production was mainly increased in the upper compartment that corresponds to a Sertoli cell apical flux. In this system, IL-1 and IL-6 levels were not modified by FSH; they were not also affected by residual bodies and latex beads, probably due to the fact that, in the bicameral system, phagocytosis is restricted to the Sertoli cells situated at the surface of the inner compartment. IL-1beta, but not IL-1alpha, induced IL-6 secretion in the compartment of stimulation. In conclusion, the present study demonstrates that vectorial secretory patterns of IL-1 and IL-6 production greatly differ and that these cytokines are also differently regulated. These results suggest that Sertoli IL-1 and IL-6 have different targets within the testis and that, in normal and pathophysiological conditions, both the tubular and the interstitial compartments may be influenced by the action of these paracrine factors.

Murine interleukin-11 (IL-11) is expressed at high levels in the hippocampus and expression is developmentally regulated in the testis

IL-11, derived from a bone marrow stromal cell line, has pleiotropic effects on both hematopoietic cells and nonhematopoietic cells. However, no previous studies have systematically addressed expression of IL-11 in primary tissues in vivo and the relationship of IL-11 tissue specific gene expression and function of IL-11 is not clear. In the present study, we examined constitutive IL-11 expression in various murine adult tissues in vivo. IL-11 mRNA is expressed in a wide range of normal tissues (including hematopoietic organs) at levels only detected by RT-PCR. IL-11 protein was detected in brain and testis by Western blot analysis. The in vivo cellular distribution of IL-11 expression was examined by in situ hybridization. In brain, IL-11 message is distributed in granular layer dentate gyrus and pyramidal cell layers of hippocampus. IL-11 is also expressed in anterior horn cells and lateral column neuronal cells of the spinal cord. In testis, IL-11 mRNA is expressed in round spermatids at stage VI-IX seminiferous tubules. IL-11 expression in testis is restricted to developing spermatogonia and is developmentally regulated, since no expression is seen in mice genetically deficient in germ cells and in mice prior to sexual maturation. These expression data correlate with functional data demonstrating that IL-11 stimulates proliferation in vitro of a hippocampus neuronal progenitor cell line and administration of IL-11 in vivo accelerates recovery of spermatogenesis after cytotoxic therapy. These studies suggest that IL-11 may be an important regulator in neural and testicular function.

Cell-cell interactions in the testis of teleosts and elasmobranchs

In this paper we present the state of knowledge on cell-cell interactions in the testis of two groups of anamniote vertebrates--teleosts and elasmobranchs--which include most fish. In these fish, the structural organization of the testis differs fundamentally from that which characterizes amniotes in which the germinal tissue is located in tubules open at both ends and consists of a permanent population of Sertoli cells associated with successive stages of germ cell development. In fish, the spermatogenic unit of testis is the spermatocyst, which corresponds to one germ cell or to a clone of isogenetic germ cells, enclosed by one or several Sertoli cells, which form the wall of the cyst. In fish testis, the Sertoli cells do not represent a permanent population of cells. Although both are of the cystic type, the teleost and elasmobranch testes are differently organized. In elasmobranchs, primary spermatogonia and Sertoli cells lie initially free within the interstitial tissue, before becoming sequestered by a basement membrane; the testis is then composed of a mass of spermatocysts which contain many Sertoli cells, each being associated with a clone of germ cells. In contrast, in teleosts, the cysts are confined to large elongated structures limited by a basement membrane. These structures are either lobules originating under the albuginea or tubules which, in contrast to those of mammals, are anastomosed. In the lobules, the spermatocysts start to develop at the blind end of the lobules and migrate towards the efferent system, whereas in the tubules, the spermatocysts are located against the basement membrane, all along the tubules and do not migrate. In elasmobranchs, unlike teleosts, Leydig cells are either absent from the interstitial tissue or rare and undifferentiated and their role in steroid production is at best marginal. While many studies have focused on topographical and functional interactions between the diverse cell types present in mammalian testis, only a few studies have brought particular attention to these aspects in fish. In fish, like in mammals, testicular cell-cell interactions are based on structural elements and chemical factors. Occasionally, various adhering junctions have been observed, essentially in teleosts, between Sertoli cells, between Sertoli cells and germ cells, between germ cells themselves, and interstitial cells. Furthermore, in some teleost species, using horseradish peroxidase or lanthanum salts, the presence of tight junctions between Sertoli cells has been correlated to the occurrence of a Sertoli barrier. In these species, the barrier develops after meiosis so that only haploid germ cells are shielded from the vascular system. In fish, recent development of techniques which enable the preparation and in vitro culture of enriched populations of testicular cells and of spermatocysts, has allowed investigations on functional aspects of cell-cell interactions. In particular, data have been obtained, in the trout, on the control of spermatogonia proliferation by Sertoli cell-conditioned media and, in the dogfish, on the steroidogenic activity of Sertoli cells, in relation to the differentiation stage of the associated germ cells. Furthermore information exists, in the trout, showing that intratubular macrophages may participate in the re-initiation of spermatogonial proliferation. In conclusion, the cytoarchitecture of fish testis, as compared to that of mammals, presents original features which provide unique opportunities to develop fruitful studies for a better understanding of the complex control mechanisms underlying testicular function in vertebrates.

Inflammatory mediators increase surface expression of integrin ligands, adhesion to lymphocytes, and secretion of interleukin 6 in mouse Sertoli cells

The expression of the cell adhesion molecules ICAM-1, ICAM-2, and VCAM-1 and the secretion of the cytokine interleukin 6 have been measured in mouse Sertoli cells cultured in vitro. Cytometric analysis revealed that, in basal conditions, low levels of ICAM-1 and VCAM-1 were present on the surface of the cells, whereas treatment with interleukin 1, tumor necrosis factor alpha, lipopolysaccharide, or interferon gamma induced, with different kinetics, increases in their expression. ICAM-2 was not detectable in basal conditions, nor was it inducible. Electron microscopic analysis and binding experiments using 51Cr-labeled lymphocytes demonstrated that increased expression of ICAM-1 and VCAM-1 on the surface of Sertoli cells, induced by inflammatory mediators, determines an augmented adhesion between the two cell types. The same stimuli, with the exception of interferon gamma, produced a rapid and remarkable increment of interleukin 6 production by Sertoli cells. These results suggest the presence of both direct and paracrine mechanisms of interaction between Sertoli and immune-competent cells, possibly involved in the control of immune reactions in the testis. Such mechanisms are of interest for the understanding of autoimmune pathologies of the testis and, if confirmed in humans, they could be involved in the sexual transmission of human immunodeficiency virus infection.