Uropathogenic Escherichia coli Infection Compromises the Blood-Testis Barrier by Disturbing mTORC1-mTORC2 Balance

The structural and functional destruction of the blood-testis barrier (BTB) following uropathogenic E. coli (UPEC) infection may be a critical component of the pathologic progress of orchitis. Recent findings indicate that the mammalian target of the rapamycin (mTOR)-signaling pathway is implicated in the regulation of BTB assembly and restructuring. To explore the mechanisms underlying BTB damage induced by UPEC infection, we analyzed BTB integrity and the involvement of the mTOR-signaling pathway using in vivo and in vitro UPEC-infection models. We initially confirmed that soluble virulent factors secreted from UPEC trigger a stress response in Sertoli cells and disturb adjacent cell junctions via down-regulation of junctional proteins, including occludin, zonula occludens-1 (ZO-1), F-actin, connexin-43 (CX-43), β-catenin, and N-cadherin. The BTB was ultimately disrupted in UPEC-infected rat testes, and blood samples from UPEC-induced orchitis in these animals were positive for anti-sperm antibodies. Furthermore, we herein also demonstrated that mTOR complex 1 (mTORC1) over-activation and mTORC2 suppression contributed to the disturbance in the balance between BTB "opening" and "closing." More importantly, rapamycin (a specific mTORC1 inhibitor) significantly restored the expression of cell-junction proteins and exerted a protective effect on the BTB during UPEC infection. We further confirmed that short-term treatment with rapamycin did not aggravate spermatogenic degeneration in infected rats. Collectively, this study showed an association between abnormal activation of the mTOR-signaling pathway and BTB impairment during UPEC-induced orchitis, which may provide new insights into a potential treatment strategy for testicular infection.

Injury to the blood-testis barrier after low-dose-rate chronic radiation exposure in mice

Exposure to ionising radiation induces male infertility, accompanied by increasing permeability of the blood-testis barrier. However, the effect on male fertility by low-dose-rate chronic radiation has not been investigated. In this study, the effects of low-dose-rate chronic radiation on male mice were investigated by measuring the levels of tight-junction-associated proteins (ZO-1 and occludin-1), Niemann-Pick disease type 2 protein (NPC-2) and antisperm antibody (AsAb) in serum. BALB/c mice were exposed to low-dose-rate radiation (3.49 mGy h(-1)) for total exposures of 0.02 (6 h), 0.17 (2 d) and 1.7 Gy (21 d). Based on histological examination, the diameter and epithelial depth of seminiferous tubules were significantly decreased in 1.7-Gy-irradiated mice. Compared with those of the non-irradiated group, 1.7-Gy-irradiated mice showed significantly decreased ZO-1, occludin-1 and NPC-2 protein levels, accompanied with increased serum AsAb levels. These results suggest potential blood-testis barrier injury and immune infertility in male mice exposed to low-dose-rate chronic radiation.

Blood-tissue barriers: morphofunctional and immunological aspects of the blood-testis and blood-epididymal barriers

The blood-testis barrier (BTB) is known for its ability to create an immune privilege site in the seminiferous epithelium, but less is known of the blood-epididymal barrier (BEB). It is already established that the fully functional BTB and BEB are much more complex and consist of anatomical/physical (tight junctions, basolateral and apical membranes), physiological and immunological components, which are all necessary to make a functioning barrier in the testis and epididymis. However, comparative data for metazoans suggest that an effective Sertoli cell barrier is not entirely necessary for the development of germ cells during spermatogenesis or that our knowledge about the barrier structure/function in metazoans is still immature. This chapter compares the unique barrier formed by the Sertoli cells of the testis to that formed by the apical junctional complexes of the epididymal epithelium.

The blood-testis barrier and its implications for male contraception

The blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in the mammalian body. It divides the seminiferous epithelium into the basal and the apical (adluminal) compartments. Meiosis I and II, spermiogenesis, and spermiation all take place in a specialized microenvironment behind the BTB in the apical compartment, but spermatogonial renewal and differentiation and cell cycle progression up to the preleptotene spermatocyte stage take place outside of the BTB in the basal compartment of the epithelium. However, the BTB is not a static ultrastructure. Instead, it undergoes extensive restructuring during the seminiferous epithelial cycle of spermatogenesis at stage VIII to allow the transit of preleptotene spermatocytes at the BTB. Yet the immunological barrier conferred by the BTB cannot be compromised, even transiently, during the epithelial cycle to avoid the production of antibodies against meiotic and postmeiotic germ cells. Studies have demonstrated that some unlikely partners, namely adhesion protein complexes (e.g., occludin-ZO-1, N-cadherin-β-catenin, claudin-5-ZO-1), steroids (e.g., testosterone, estradiol-17β), nonreceptor protein kinases (e.g., focal adhesion kinase, c-Src, c-Yes), polarity proteins (e.g., PAR6, Cdc42, 14-3-3), endocytic vesicle proteins (e.g., clathrin, caveolin, dynamin 2), and actin regulatory proteins (e.g., Eps8, Arp2/3 complex), are working together, apparently under the overall influence of cytokines (e.g., transforming growth factor-β3, tumor necrosis factor-α, interleukin-1α). In short, a "new" BTB is created behind spermatocytes in transit while the "old" BTB above transiting cells undergoes timely degeneration, so that the immunological barrier can be maintained while spermatocytes are traversing the BTB. We also discuss recent findings regarding the molecular mechanisms by which environmental toxicants (e.g., cadmium, bisphenol A) induce testicular injury via their initial actions at the BTB to elicit subsequent damage to germ-cell adhesion, thereby leading to germ-cell loss, reduced sperm count, and male infertility or subfertility. Moreover, we also critically evaluate findings in the field regarding studies on drug transporters in the testis and discuss how these influx and efflux pumps regulate the entry of potential nonhormonal male contraceptives to the apical compartment to exert their effects. Collectively, these findings illustrate multiple potential targets are present at the BTB for innovative contraceptive development and for better delivery of drugs to alleviate toxicant-induced reproductive dysfunction in men.

The presence of intra-tubular lymphocytes in normal testis of the mouse

Spermatoza contain various autoimmunogenic materials, which are recognized as foreign by the self immune system. Therefore, the blood-tesits-barrier (BTB) formed by Sertoli cells, basal lamina and myoid cells protects autoimmunogeneic spermatozoa from attack by the self immune system. However, the BTB at the tubuli recti (TR) and the rete testis (RT) is known to be incomplete against humoral substances. We investigated here whether the BTB is physiologically penetrated by lymphocytes in mice. We performed light and electron microscopical observation of the seminiferous tubules (ST), the TR and the RT in normal C3H/IHe mice. Although no lymphocytes were observed inside the ST, a very few lymphocytes could be found beyond the basal lamina of the TR and the RT. These lymphocytes were close to testicular spermatozoa in the TR lumen. These findings provide a possibility that lymphocytes may gain access to autoantigens of spermatozoa inside the TR and RT under physiological conditions in mice.

ETV5 is required for continuous spermatogenesis in adult mice and may mediate blood testes barrier function and testicular immune privilege

The transcription factor Ets-variant gene 5 (ETV5) is essential for spermatogonial stem cell (SSC) self-renewal, as the targeted deletion of the Etv5 gene in mice (Etv5(-/-)) results in only the first wave of spermatogenesis. Reciprocal transplants of neonatal germ cells from wild-type (WT) and Etv5(-/-) testes were performed to determine the role of ETV5 in Sertoli cells and germ cells. ETV5 appears to be needed in both cell types for normal spermatogenesis. In addition, Etv5(-/-) recipients displayed increased interstitial inflammation and tubular involution after transplantation. Preliminary studies suggest that the blood-testis barrier (Sertoli-Sertoli tight junctional complex) is abnormal in the Etv5(-/-) mouse.

[Immune-testicular regulation and cytokines]

The pathogenesis of male infertility can be reflected in alterations of spermatogenesis caused by testicular cancer, aplasia of the germinal cells, varicocele, environmental factors or defect in the transport of the sperms, among others. In general, 48% of men suffer unexplained infertility. During a long time, the masculine reproductive tract and the immune system have been studied as different and independent systems. However, in the last two decades a particular interest has arisen in the interaction of both systems on masculine infertility, in particular in the evaluation of antisperm antibodies as a common cause of infertility. Also, the inflammation due to genital or systemic infections can cause alterations in the testicular function. The recognition of intratesticular antigens provokes the production of antibodies by B lymphocytes. Then, the immune system induces a cellular response, by cytokines secretion, activation of complement and T lymphocytes activation. In this review the components and the immune system response mechanism, the organization of the testicle as a reproductive organ and the mediators of the immunologic response will be examined: interleukin-1 (IL-1), IL-6, leukaemia Inhibitory factor, tumor necrosis factor-alpha, the molecule FasL (CD95L) and Fas (CD95), macrophage migration-inhibitory factor, mononuclear phagocyte colony stimulating factor, Granulocyte/macrophage colony stimulating factor, as well as stem cell factor, interferon, transforming growth factor B and activins.

Spermatogenic cells distal to the blood-testis barrier in rats lack C3 convertase regulators and may be at risk of complement-mediated injury

On most tissues, multiple membrane complement regulators (CReg) protect self-cells from damage by complement. An exception is the brain, where the blood-brain barrier provides a protected environment within which cells survive with little or no protection from complement. The testis has a functionally similar structure, the blood-testis barrier (BTB). Here, we have investigated the expression of C3/C5 convertase CReg and C3 in the normal rat testis at different ages and different spermatogenetic stages, as well as in rats in which spermatogenesis and the BTB were impaired due to a developmental deficit. Immature testis, prior to BTB formation at puberty, displayed broad expression of the ubiquitous rodent CReg Crry on all elements and no expression of CD46 or CD55. Within days of BTB formation, CReg expression was dramatically altered; Crry was expressed only in the spermatogenetic cells external to the BTB in basal layers of adult seminal epithelium. Spermatogenic cells immediately distal to the BTB at first expressed no C3/C5 convertase regulators but later acquired expression of CD46 and CD55. Staining for C3 was widespread pre-puberty, but absent distal to the BTB in mature rats. In rats with defects in spermatogenesis and BTB integrity, expression patterns of CReg and C3 resembled those in pre-pubertal normals. The relative paucity of CReg and absence of C3 synthesis distal to the BTB suggest the presence of a complement-protected environment analogous to that described in the brain, and suggest also that cells enclosed by the BTB may be susceptible to complement damage when the barrier is breached.

Macrophages and the immune responsiveness of the testis

Immune responses within the testis are regulated in a manner that provides protection for the developing male germ cells, while permitting qualitatively normal inflammatory responses and protection against infection. The large population of resident-type macrophages in the testis is strongly implicated in mediating this specialised immunological environment. Several studies in the rat have shown that testicular macrophages retain their cytotoxic and phagocytic capacity, but have greatly diminished pro-inflammatory function and even exhibit immunosuppressive activity. While the local mechanisms that control the phenotype of the testicular macrophage population are unknown, evidence points to the influence of the testicular somatic cells, the Sertoli and Leydig cells. A smaller but significant population of macrophages that lack expression of resident macrophage markers, is also found in the rat testis. The functional role of these macrophages remains to be defined, but they most likely represent circulating monocytes or newly-arrived testicular macrophages, and, therefore, may contribute to sustaining inflammatory responses within the testis. Further investigation of the immune-related functions of these different macrophage subsets, and the testicular somatic cells, during immunological and inflammatory events should provide a better understanding of how the testicular immune environment is maintained and regulated.

An oncological view on the blood-testis barrier

The function of the blood-testis barrier is to protect germ cells from harmful influences; thus, it also impedes the delivery of chemotherapeutic drugs to the testis. The barrier has three components: first, a physicochemical barrier consisting of continuous capillaries, Sertoli cells in the tubular wall, connected together with narrow tight junctions, and a myoid-cell layer around the seminiferous tubule. Second, an efflux-pump barrier that contains P-glycoprotein in the luminal capillary endothelium and on the myoid-cell layer; and multidrug-resistance associated protein 1 located basolaterally on Sertoli cells. Third, an immunological barrier, consisting of Fas ligand on Sertoli cells. Inhibition of P-glycoprotein function offers the opportunity to increase the delivery of cytotoxic drugs to the testis. In the future, visualisation of function in the blood-testis barrier may also be helpful to identify groups of patients in whom testis conservation is safe or to select drugs that are less harmful to fertility.

Expression of a blood-brain barrier-specific antigen in the reproductive tract of the male rat

The endothelial barrier antigen (EBA) is a protein expressed specifically by the endothelial cells of the rat brain barrier vessels. This antigen has been described as a 'barrier protein' and is used as a marker for the competent blood-brain barrier. A blood-testis barrier has also been described. However, unlike the blood-brain barrier, which is formed by endothelial cells, the blood-testis barrier is formed mainly by the Sertoli cells, which provide an isolated environment for spermatogenic cells within the seminiferous tubules. Testicular blood vessels express the erythroid glucose transporter protein and other markers, which are strongly expressed in brain blood vessels, and may contribute to the blood-testis barrier. This study was carried out to determine whether Sertoli cells or testicular blood vessels express EBA. Tissues of other organs were used as controls for EBA expression. EBA was expressed by the endothelial cells in most microvessels of the testis, and in a few vessels of the epididymis, seminal vesicle, prostate gland, vas deferens and bladder-neck region. Furthermore, EBA was strongly and consistently detected in epithelial cells of the rete testis and dorsolateral prostate gland, and in a few epithelial cells of the ventral prostate gland, the seminal vesicle and the coagulating gland. However, Sertoli cells, which are the main site of the blood-testis barrier, were negative for EBA. In conclusion, EBA may have a wider role in rat tissues than has been previously appreciated.

[Surgical and experimental-biological aspects of inguinal hernia]

In experiment on 57 animals the method of plasty of anterior wall of inguinal channel by forming of the aponeurosis of m. abdominis obliqus ext. and suturing together the aponeurotic edges was simulated. The results of surgical correction of inguinal hernia in 257 patients were analysed. The correlational connection of immunological changes in organism with the degree of destructive changes of hematotesticular barrier (HTB) and spermatogenic epithelium was established. Considering the testicle autoimmunity the application of protective operative methods of pharmacological defense of HTB and spermatogenic epithelium are proposed.