Reproductive effects of chronic administration of murine interferon-gamma

Responses of testosterone hormone concentration, semen quality, and its related pro-inflammatory cytokines in bucks following Corynebacterium pseudotuberculosis and its mycolic acid infection

Corynebacterium pseudotuberculosis is the causative agent of caseous lymphadenitis, a debilitating chronic disease of sheep and goats. Little is known about the buck's reproductive pathophysiology with respect to inoculation with Corynebacterium pseudotuberculois and its immunogen mycolic acid extract. Therefore, this present study was designed to determine the concentration of testosterone hormone, pro-inflammatory cytokines, and semen quality of the experimental animals. A total of 12 bucks, divided into groups 1, 2, and 3 (Negative control group, Positive control group and Mycolic acid group respectively), were enrolled in this study. Following inoculation, all goats were observed for clinical responses and monitored for 60 days post-challenge and were then sacrificed. Blood samples were collected via the jugular once before inoculation and on a weekly basis post-challenge. Semen samples were collected 2 weeks post-challenge and prior to the sacrifice of the experimental animals. During the post inoculation period of 60 days, the concentration of testosterone hormone for group 2 was increased significantly (p < 0.05) in weeks 5, 6, and 9 but decreased in weeks 2 and 7 post inoculation. In group 3, the mean concentration of testosterone was increased significantly (p < 0.05) in weeks 5, 6, 7, and 9 post inoculation but decreased in week 2. The concentration of interleukin 6 (IL 6) in treated group 2 did not show any significant difference (p > 0.05) but increased significantly (p < 0.05) in week 2 post inoculation in group 3. For concentration of interleukin 1β (IL1β) in both treated groups 2 and 3 showed significant difference (p < 0.05) in weeks 2 and 3 post inoculation. The tumor necrosis factor-alpha (TNF-α) concentration in both treated groups 2 and 3 did not show any significant difference (p > 0.05) as compared to group 1. The concentration of interferon-γ (IFNγ) significantly increased (p < 0.05) for group 2 for weeks 2, 3, 4, and 5 where else for group 3 was not in significant difference (p > 0.05) compared to group 1. Both group 2 and group 3 showed a reduction in semen qualities as compared to group 1, but the severity was more intense in group 2 if compared to group 3. In conclusion, therefore, the present study concluded that the mycolic acid group revealed significant responses of testosterone hormone concentration, semen quality, and its related pro-inflammatory cytokines in bucks following infection but the severity lesser compared to Corynebacterium pseudotuberculosis group.

Synergistic effect of interferon-gamma and tumor necrosis factor-alpha on coxsackievirus and adenovirus receptor expression: an explanation of cell sloughing during testicular inflammation in mice

Coxsackievirus and adenovirus receptor (CAR) is a junction molecule that expresses on Sertoli and germ cells. It mediates Sertoli-germ cell adhesion and facilitates migration of preleptotene/leptotene spermatocytes across the blood-testis barrier, suggesting that CAR-based cell adhesion and migration are crucial for spermatogenesis. Interferon-gamma (IFNG) and tumor necrosis factor alpha (TNF) are two major cytokines that are elevated during testicular inflammation and cause reduced fertility. We investigated the mechanism by which IFNG and TNF exert their disruptive effects on testicular cell adhesion. We have demonstrated that combined treatment with IFNG and TNF (IFNG+TNF) exerts a synergistic effect by downregulating CAR mRNA and protein levels. Immunofluorescence staining revealed that IFNG+TNF treatment effectively removes CAR from the site of cell-cell contact. Using inhibitor and co-immunoprecipitation, we confirmed that IFNG+TNF mediates CAR protein degradation via ubiquitin-proteasome and NFKB pathways. Blockage of ubiquitin-proteasome pathway significantly inhibits CAR degradation, as indicated by the reappearance of CAR at the site of cell-cell contact. Additionally, IFNG+TNF reduces CAR mRNA via transcriptional regulation. Mutational studies have shown that IFNG+TNF-induced CAR repression is achieved by suppression of the basal transcription. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays further confirmed that IFNG+TNF treament not only inhibits binding of the basal transcription factors but also promotes binding of NFKB subunits and Sp1 (negative regulators) to the CAR promoter region. Taken together, IFNG+TNF treatment significantly downregulates CAR expression, which provides an explanation of how cell sloughing in the epithelium mediates, by loss of CAR-based cell adhesion, during testicular inflammation.

Exogenous administration of recombinant human FSH does not improve germ cell survival in human prepubertal xenografts

In a previous study, meiotic activity was observed in human intratesticular xenografts from peripubertal patients. However, full spermatogenesis could not be established. The present study aimed to evaluate whether the administration of recombinant human FSH could improve the spermatogonial survival and the establishment of full spermatogenesis in intratesticular human xenografts. Human testicular tissue was obtained from six boys (aged 2.5-12.5years). The testicular biopsy was fragmented and one fragment of 1.5-3.0mm(3) was transplanted to the testis of immunodeficient nude mice. Transplanted mice were assigned to different experimental groups to enable evaluation of the effects of FSH administration and freezing. The structural integrity of the seminiferous tubules, the spermatogonial survival and the presence of differentiated cells were evaluated by histology and immunohistochemistry. Freezing or administration of FSH did not influence tubule integrity and germ cell survival in human xenografts. Meiotic germ cells were observed in the xenografts. More tubules containing only Sertoli cells were observed in frozen-thawed grafts, and more tubules with meiotic cells were present in fresh grafts. There was no clear influence of FSH treatment on meiotic differentiation. Administration of FSH did not improve the establishment of full spermatogenesis after intratesticular tissue grafting.

Meiotic activity in orthotopic xenografts derived from human postpubertal testicular tissue

BACKGROUND

Grafting of frozen-thawed testicular tissue has been suggested as a novel fertility preservation method for patients undergoing gonadotoxic treatments. However, this technique still needs further optimization before any clinical application. So far, grafting of human testicular tissue has only been performed to the back skin of nude mice and has shown spermatogonial stem-cell survival and occasionally differentiation up to primary spermatocytes. In this study, orthotopic grafting to mouse testes was evaluated as an alternative, and the effect of freezing and the donor's age was studied.

METHODS

Human testicular tissue was obtained from two prepubertal (aged 3 and 5) and two postpubertal (aged 12 and 13) boys. Both fresh and frozen-thawed testicular tissue was grafted to the testis of immuno-deficient nude mice. Four and nine months after transplantation, testes were analyzed by histology and immunohistochemistry.

RESULTS

Four and nine months after transplantation, spermatogonial stem cells were observed in all tissue grafts. Germ cell survival was found to be higher in xenografts from the older boys when compared with that from younger donors. Furthermore, no differentiation was observed in the xenografts from younger patients, but the grafts of two older donors showed differentiation up to the primary spermatocyte level, with the presence of secondary spermatocytes in the oldest donor 9 months after transplantation.

CONCLUSIONS

This xenografting study shows that intratesticular grafting results in high germ cell survival. In grafts derived from the older boys, meiotic activity was maintained in the xenografts for at least 9 months. Although difficult to conduct due to the scarcity of the tissue, more comparative research is needed to elucidate an optimal grafting strategy.

Alternative Strategies for Toxicity Testing of Species-Specific Biopharmaceuticals

Although toxicology studies should always be conducted in pharmacologically relevant species, the specificity of many biopharmaceuticals can present challenges in identification of a relevant species. In certain cases, that is, when the clinical product is active only in humans or chimpanzees, or if the clinical candidate is active in other species but immunogenicity limits the ability to conduct a thorough safety assessment, alternative approaches to evaluating the safety of a biopharmaceutical must be considered. Alternative approaches, including animal models of disease, genetically modified mice, or use of surrogate molecules, may improve the predictive value of preclinical safety assessments of species-specific biopharmaceuticals, although many caveats associated with these models must be considered. Because of the many caveats that are discussed in this article, alternative approaches should only be used to evaluate safety when the clinical candidate cannot be readily tested in at least one relevant species to identify potential hazards.

Immune-endocrine interactions and Leydig cell function: the role of cytokines

Inflammatory disease is known to affect male reproductive function and fertility. Male accessory gland infections (MAGI) account for almost 15% of all cases of male infertility seen in infertility clinics. Infections of the male accessory glands are associated with increased counts of white blood cells in semen and elevated levels of pro-inflammatory cytokines in the semen and the testis. Numerous studies have underscored the importance of cytokines in the regulation of testicular and glandular function during pathophysiological events as well as under normal physiological conditions when cytokines act as growth and differentiation factors. The purpose of this paper is to particularly review the role of cytokines in the regulation of Leydig cell function in the testis primarily under pathophysiological conditions, and also considers clinical investigations that help to improve the evaluation and treatment of male infertility.

Interferon-gamma therapy: evaluation of routes of administration and delivery systems

Although different routes and delivery systems have been used to deliver interferon-gamma (IFN-gamma) for the treatment of a variety of viral and neoplastic diseases, little has been reported regarding the most efficient and least toxic routes and drug delivery modes required to achieve these goals. To have a greater understanding of the best strategies to use to administer this cytokine in an efficient, stable, and safe manner, this review details aspects of IFN-gamma concerning its mechanism of action, physical properties, and pharmacokinetics. One important conclusion that is drawn from this analysis is that a consistent, local concentration of IFN-gamma is necessary to achieve an optimal therapeutic response. A critical discussion covering the advantages and limitations of the currently used methodologies to deliver IFN-gamma in such a fashion is presented.

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.

Growth hormone regulates steroidogenic acute regulatory protein expression and steroidogenesis in Leydig cell progenitors

Gonadal development and differentiation is dependent in part on GH, as GH deficiency has been implicated as a cause of lowered fertility and spermatogenic cessation in humans and some biological models. In this study, we demonstrate that GH receptor messenger RNA (mRNA) is preferentially expressed in progenitor Leydig cells (PLCs) isolated and purified from 21-day-old rats. GH induces significant increases in the levels of steroidogenic acute regulatory protein (StAR), 3beta-hydroxysteroid dehydrogenase (3beta-HSD) expression, and androgen production in PLCs. Additionally, the cytokine interferon-gamma (IFNgamma) markedly inhibits GH-stimulated StAR mRNA and protein levels. When cells are cultured with both GH and IFNgamma, IFNgamma decreases the stimulating effect of GH on androgen production. Treatment of PLCs with cycloheximide does not prevent the GH-induced StAR mRNA, indicating that GH induction of StAR transcripts does not require de novo protein synthesis. In contrast, the induction of 3beta-HSD mRNA by GH is altered by cycloheximide treatment. H7, a serine/threonine kinase inhibitor, completely abrogates the increases in StAR mRNA by GH, whereas the tyrosine kinase inhibitor genistein does not. Moreover, GH further enhances StAR and 3beta-HSD mRNA expression in isolated adult rat Leydig cells despite their increased basal expression subsequent to maturational acquisition of these steroidogenic components. These data provide the first demonstration of the direct effects of GH on testicular steroidogenesis during progenitor Leydig cell differentiation.

Identification and regulation of testicular interferon-gamma (IFNgamma) receptor subunits: IFNgamma enhances interferon regulatory factor-1 and interleukin-1beta converting enzyme expression

Interferon-gamma (IFNgamma) transmits its signal through a specific cell surface receptor (IFNgammaR), which consists of a primary ligand binding alpha-chain (IFNgammaR alpha) and a signaling beta-chain (IFNgammaR beta). Recent studies identified the cytokines IFNgamma, interleukin-6 (IL-6), IL-1alpha, and tumor necrosis factor-alpha in testicular cells. Therefore, we: 1) examined the expression of IFNgammaR alpha and IFNgammaR beta subunits in freshly isolated and purified rat testicular cells; 2) examined the differential regulation of receptor components by cytokines using primary cultures of Sertoli cells; 3) identified the cell signaling pathway components of testicular IFNgammaR; and 4) characterized the functional role of testicular IFNgamma using primary Sertoli cells. We demonstrated the messenger RNAs for both chains of IFNgammaR in rat testicular cells using Northern hybridization analysis. Western blot analysis and immunocytochemistry showed that both specific IFNgammaR protein subunits were present in cultured primary Leydig and Sertoli cells prepared from the testes of immature rats. The expression of both IFNgammaR component messenger RNAs in cultured Sertoli cells was increased by its specific ligand (IFNgamma), as well as IL-1alpha and tumor necrosis factor-alpha, in both a time- and dose-dependent manner. IFNgamma-activation of the Janus (JAK) tyrosine kinases, JAK1 and JAK2 proteins, indicate that IFNgammaR, expressed in the Sertoli cell, is functional. Moreover, IFNgamma modulates the expression of interferon regulatory factor (IRF)-1 and IL-1beta converting enzyme genes in Sertoli cells. Thus, our data are suggestive of a role(s) for IFN-gamma in the regulation of distinct gene expression and cell-specific sensitivity to apoptosis in the testis.

Interferon-gamma inhibits the steroidogenic acute regulatory protein messenger ribonucleic acid expression and protein levels in primary cultures of rat Leydig cells

Interferon-gamma (IFNgamma) is an immunomodulating cytokine that has profound effects on reproductive function. IFNgamma inhibits steroidogenesis both in vivo and in vitro. The mechanism by which IFNgamma inhibits Leydig cell steroidogenesis remains unclear. In the present study, we evaluated the effect of IFNgamma on the expression and regulation of the steroidogenic acute regulatory protein (StAR) gene in primary cultures of rat Leydig cells. StAR facilitates the efficient production of steroid hormone by regulating the translocation of cholesterol from the outer to the inner mitochondrial membrane, the site of the cytochrome P450 side-chain cleavage (P450scc) enzyme system that converts cholesterol to pregnenolone. IFNgamma inhibited hCG-induced StAR messenger RNA (mRNA) levels in a dose-dependent manner. The addition of IFNgamma in a concentration of 500 U/ml decreased hCG-induced 3.8- and 1.7-kilobase StAR mRNA by 78% and 70%, respectively. IFNgamma also reduced hCG-stimulated P450scc mRNA levels by 69%. The inhibitory effects of IFNgamma on StAR mRNA levels were confirmed by ribonuclease protection assay. As early as 12 h after the addition of IFNgamma, hCG-induced StAR mRNA levels decreased by more than 44%. To evaluate the effects of IFNgamma on StAR protein levels, Western blot analyses were performed. hCG in a concentration of 10 ng/ml increased StAR protein by 5.6-fold. Treatment of Leydig cells with IFNgamma (500 U/ml) decreased hCG-induced StAR protein by 44%. In contrast, interleukin-1 and murine tumor necrosis factor-alpha reduced hCG-induced P450scc mRNA expression without inhibiting StAR mRNA or protein levels. In conclusion, IFNgamma inhibits Leydig cell steroidogenesis by down-regulating StAR gene expression and protein production.