Tumor necrosis factor-alpha enhances inhibitory effects of interleukin-1 beta on Leydig cell steroidogenesis

Safflower seed oil improves steroidogenesis and spermatogenesis in rats with type II diabetes mellitus by modulating the genes expression involved in steroidogenesis, inflammation and oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus (DM), as a multiorgan syndrome, is an endocrine and metabolic disorder that is associated with male reproductive system dysfunction and infertility. Safflower (Carthamus tinctorius L.) as an herbal remedy improves DM and infertility-related disorders. The anti-hypercholesterolemic, anti-inflammatory, and antioxidative properties of this herb have been well documented, but its role in testosterone production, male reproductive system and zinc homeostasis has not been fully illustrated.

AIM OF THE STUDY

This study aimed to investigate the preventive and therapeutic properties of different doses of safflower seed oil against reproductive damage caused by type II DM by investigating zinc element homeostasis, inflammation and oxidative damage in testis tissue and their relationship with testosterone production and sperm parameters.

MATERIALS AND METHODS

Eighty adult male Sprague-Dawley rats were randomly divided into eight groups and treated daily for 12 and 24 weeks in protective and therapeutic studies, respectively. Type II DM was induced by a High Fat Diet (HFD) in normoglycemic rats for three months. At the end of each study, serum level of glucose, testosterone, gonadotropins, TNF-α, insulin, and leptin were measured. Moreover, antioxidant enzymes activity, lipid peroxidation, zinc and testosterone along with the expression of Nrf-2, NF-κB, TNF-α, StAR, P450scc, and 17βHSD3 genes in the testis were detected.

RESULTS

After the intervention, the activity of antioxidant enzymes and the level of testosterone and gonadotropins significantly decreased in the rats with DM in comparison to the others. However, lipid peroxidation and serum level of insulin, leptin and TNF-α increased and the testicular level of zinc significantly changed in the rats with DM compared to the control groups (p < 0.05). The gene expression of NF-κB and TNF-α were also significantly increased and the gene expression of Nrf2, StAR, P450scc and 17βHSD3 were decreased in the testis of diabetic rats (p < 0.05). The results showed that pretreatment and treatment with safflower seed oil could improve these parameters in diabetic rats compared with untreated diabetic rats (p < 0.05).

CONCLUSION

HFD could impair the production of testosterone and sperm, and reduce gonadotropin by increasing the serum level of leptin and inducing insulin resistance, oxidative stress and inflammation. However, safflower oil in a dose-dependent manner could improve testosterone level and sperm parameters by improving the level of leptin, zinc and insulin resistance, and the genes expression involved in testosterone synthesis, inflammation and oxidative stress.

Alteration of testicular regulatory and functional molecules following long-time exposure to 900 MHz RFW emitted from BTS

The aim of this investigation was to evaluate changes in testosterone and some of the functional and regulatory molecules of testis such as P450scc, steroidogenic acute regulatory protein (StAR), tumour necrosis factor-α (TNF-α), interleukin-1α (IL-1α), interleukin-1β (IL-1β) and nerve growth factor (NGF) following exposure to 900 MHz radio frequency (RF). Thirty adult male Sprague Dawley rats (190 ± 20 g BW) were randomly classified in three equal groups, control (sham, without any exposure), short-time exposure (2 hr) (STE) and long-time exposure (4 hr) (LTE). The exposure was performed for 30 consecutive days. The testosterone level in both exposed groups was significantly less than control (p < .05). Level of TNF-α in both exposed groups was significantly greater than control (p < .05). IL-1α and NGF levels in LTE were significantly higher than the STE and control groups (p < .05). Level of IL-1β in LTE was significantly higher than control (p < .05). Expression of both P450scc and StAR mRNA was significantly down-regulated in both exposed groups compared to control (p < .05). Our results showed that RFW can affect testis and reproductive function through changes in factors, which are important during steroidogenesis, and also through changes in inflammatory factors, which regulate Leydig cell functions.

Infectious, inflammatory, and immunologic conditions resulting in male infertility

This article provides an overview of infectious and inflammatory conditions associated with male infertility. These conditions may affect several components of the male reproductive tract and therefore have the ability to potentially alter sperm function. The effect of these conditions on male fertility is poorly understood and often underestimated.

CD4+ and CD8+ T cells producing Th1 and Th17 cytokines are involved in the pathogenesis of autoimmune orchitis

Experimental autoimmune orchitis (EAO) is a useful model to study chronic testicular inflammation and infertility. EAO is characterized by severe damage of seminiferous tubules with germ cells that undergo apoptosis and sloughing. We previously reported an increase in CD4+ and CD8+ effector T cells in the testes of rats with EAO. Since cytokine patterns determine T cell effector functions, in the present work we analyzed the cytokines expressed by these cells during disease development. By flow cytometry, we detected an increase in the number of tumor necrosis factor-α (TNF) and interferon -γ (IFNG)-producing CD4+ T cells in the testis at EAO onset. As the severity of the disease progressed, these cells declined while CD8+ T cells producing TNF and IFNG increased, with the predominance of IFNG expression. As a novel finding, we identified by immunofluorescence CD4+ interleukin 17 (IL17)+ and CD8+ IL17+ cells in the testes of EAO rats, with CD4+ and CD8+ T cells predominating at the onset and in the chronic phase of EAO respectively. Moreover, IL17 (western blot) and IL23 content (ELISA) increased in EAO, with maximum levels in the chronic phase. These results suggest the involvement of CD4+ T helper (Th) 1 and Th17 subsets as co-effector cells governing EAO onset, as well as the central contribution of CD8+ T cells producing Th1 and Th17 cytokines in the maintenance of chronic inflammation. The expression of T-bet and RORγt (western blot) in the testis over the course of disease also supports the presence of Th1 and Th17 cells in the testes of EAO rats.

Cytokine knockouts in reproduction: the use of gene ablation to dissect roles of cytokines in reproductive biology

Cytokines play many diverse and important roles in reproductive biology, and dissecting the complex interactions between these proteins and the different reproductive organs is a difficult task. One approach is to use gene ablation, or 'knockout', to analyse the effect of deletion of a single cytokine on mouse reproductive function. This review summarizes the essential roles of cytokines in reproductive biology that have been revealed by gene knockout studies, including development and regulation of the hypothalamo-pituitary-gondal axis, ovarian folliculogenesis, implantation and immune system modulation during pregnancy. However, successful utilization of this approach must consider the caveats associated with gene ablation studies, e.g. embryonic lethality, systemic effects of cytokine ablation on local reproductive processes and the limited exposure to pathogens in mice housed in laboratory conditions. New sophisticated technology that temporally or spatially regulates gene ablation can overcome some of these limitations. Discoveries on the roles of cytokines in reproductive function uncovered by gene ablation studies can now be applied to improve in vitro fertilization for infertile couples and in the development of contraceptive therapies.

Epididymal Stone Formation and Decreased Sperm Production in Roosters Vaccinated with a Killed Strain of Avian Infectious Bronchitis Virus

Our objective was to determine if vaccination with killed avian infectious bronchitis virus (AIBV) causes epididymal calcium stones in the rooster as is seen following vaccination with live attenuated AIBV. Specific-pathogen-free roosters were divided into three groups: nonvaccinated (NONVAC), live attenuated AIBV-vaccinated (LVAC), and killed AIBV-vaccinated (KVAC) groups. Roosters were vaccinated at 2, 6, 10, and 14 wk of age and the epididymal region was observed at 27 wk of age. Epididymal stones were present in 13% of NONVAC, 50% of KVAC, and 64% of LVAC roosters. Histologically, immune cells were seen in the interstitium of efferent ductules containing stones. We conclude that use of a killed vaccine does not reduce the incidence of epididymal stones.

Infliximab may reverse the toxic effects induced by tumor necrosis factor alpha in human spermatozoa: an in vitro model

OBJECTIVE

To examine the toxic effects of tumor necrosis factor alpha (TNF-alpha) on ejaculated spermatozoa and evaluate the ability of infliximab to reverse these effects.

DESIGN

Prospective controlled study.

SETTING

Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Thirty-one healthy sperm donors.

INTERVENTION(S)

Exposure of human spermatozoa to varying concentrations of TNF-alpha (100, 300, 400, 500 pg/mL, and 2.5 microg/mL) and infliximab (400 microg/mL).

MAIN OUTCOME MEASURE(S)

Sperm motility, functional integrity of plasma membrane, and DNA fragmentation.

RESULT(S)

Spermatozoa quality declined following incubation with TNF-alpha in a dose-dependent and time-dependent manner. Sperm motility and membrane integrity were higher in the samples incubated with TNF-alpha plus infliximab than in the samples treated with TNF-alpha only. These parameters improved significantly and were comparable with both controls and sperm incubated with infliximab alone. Similarly, the percentage of spermatozoa with DNA fragmentation improved significantly following incubation with TNF-alpha plus infliximab and again was comparable with both controls and sperm incubated with infliximab alone.

CONCLUSION(S)

Spermatozoa may be exposed to abnormal levels of TNF-alpha in the male reproductive tract or during their passage into the female reproductive tract (in cases of endometriosis). Exposing spermatozoa to pathological concentrations of TNF-alpha can result in significant loss of their functional and genomic integrity. Infliximab could potentially be used to help treat female infertility caused by endometriosis in those with elevated levels of TNF-alpha in their peritoneal fluid.

Neonatal lead exposure changes quality of sperm and number of macrophages in testes of BALB/c mice

BALB/c mice were exposed to 0.1 ppm lead acetate in the drinking water from postnatal day (PND) 1 for 6 weeks. Until PND21, lead exposure was from mother's milk; thereafter, it was directly from the drinking water. The blood lead levels were the highest in pups before weaning (59.5+/-0.9 microg/dL) and significantly lower between PND21 and PND42 (20.3+/-4.7 microg/dL). At PND42, lead-exposed male mice were tested for fertility, sperm DNA, and macrophage number. Mating of lead-treated males with non-treated females confirmed the reduction of fertility in the exposed males. Flow cytometric studies of testicular preparations indicated that the sperm count was not different between lead-exposed and control males; however, the lead-treated mice had a significant increase in the number of testicular cells having a < 1n amount of DNA, which coincided with a decrease in the number of testicular cells with a 2n and 4n amount of DNA. The number of testicular macrophages also was decreased in lead-exposed males, which could reflect altered levels of CSF-1 or response to CSF-1, as previously reported [Kowolenko, M., Tracy, L., Lawrence, D.A., 1989. Lead-induced alterations of in vitro bone marrow cell responses to colony stimulating factor-1. J. Leukoc. Biol. 45, 198-206]. Our study showed that exposure to 0.1 ppm of lead during the neonatal and adolescent period is sufficient to reduce fertility in adult male mice; however, it did not affect sperm count on PND42. The presence of an increased number of apoptotic (< 1n amount of DNA) testicular cells may be diagnostic of defective sperm function. Thus, an administered dose of 0.1 ppm via drinking water ingestion by neonatal male BALB/c mice sufficient to produce PbB of 20-60 mg/dL compromised reproductive function in these mice as adults.

Involvement of tumor necrosis factor-alpha in the pathogenesis of autoimmune orchitis in rats

We studied the testicular macrophages of rats with experimental autoimmune orchitis (EAO) and analyzed whether the tumor necrosis factor-alpha (TNFalpha) is involved in germ cell apoptosis and in Leydig cell steroidogenesis. The EAO was induced in adult male Sprague-Dawley rats by active immunization with testicular homogenate and adjuvants. In the experimental group, a severe orchitis was observed 80 days after the first immunization. ED1- and ED2-positive macrophages were quantified by immunohistochemistry. The TNFalpha concentration of conditioned media from testicular macrophages (TMCM) was determined by ELISA. The number of apoptotic TNF receptor 1 (TNFR1)-positive germ cells was identified by combining in situ end labeling of apoptotic DNA and immunohistochemical techniques. The effect of TNFalpha on Leydig cell testosterone production was determined by RIA. In rats with EAO, we observed a significant increase in the number of TNFalpha-positive testicular macrophages, the TNFalpha concentration in TMCM, and the number of TNFR1-positive germ cells. Sixty percent of TNFR1-positive germ cells were apoptotic. These results suggest that TNFalpha could be involved in the pathogenesis of EAO. Acting together with other local factors such as Fas-FasL, TNFalpha could trigger germ cell apoptosis. We also demonstrated that TNFalpha inhibited in vitro testosterone production in basal and hCG-stimulated Leydig cells from rats with orchitis.

Role of testicular interstitial macrophages in regulating testosterone release in hyperprolactinemia

Hyperprolactinemia-induced hypogonadism has been linked to a dysfunction of the hypothalamus-pituitary-testis axis. The direct inhibitory effects of prolactin on the testicular release of testosterone have also been demonstrated, though their mechanisms remain unclear. Incubation of rat testicular interstitial cells (TICs) with prolactin stimulated the release of testosterone. TICs from rats with anterior pituitary-grafting-induced hyperprolactinemia release lower amounts of testosterone than controls. However, Leydig cells isolated from anterior pituitary-grafted rats release a greater amount of testosterone. These paradoxical observations have remained unexplained. This study examined the roles of testicular interstitial macrophages and of their product, tumor necrosis factor-alpha (TNF-alpha), in regulating Leydig cells under condition of hyperprolactinemia. Hyperprolactinemia was induced by grafting two anterior pituitary glands of rats under the renal capsule. Control animals were grafted with rat cortex tissue. The rats were sacrificed 6 weeks later. TICs and macrophages, and Leydig cells were isolated for in vitro incubation and drugs challenge. Testosterone released by testicular interstitial or Leydig cells was measured by radioimmunoassay. TNF-alpha concentration in the medium of TICs or macrophages was measured by enzyme-linked immunosorbent assay (ELISA). A dose-dependent stimulation of TNF-alpha secretion in the medium of TICs or macrophages by the prolactin challenge was observed. Higher amounts of TNF-alpha were released by TICs in the anterior pituitary-grafted rats than in the control group. In contrast, the release of TNF-alpha by testicular interstitial macrophages isolated from the anterior pituitary- and cortex-grafted groups was quantitatively similar. Challenge with human chorionic gonadotropin did not modify the TNF-alpha release by testicular interstitial macrophages in either group. Challenge of Leydig cells with TNF-alpha inhibited their release of testosterone stimulated by human chorionic gonadotropin, but not their basal testosterone release. These different patterns of testosterone release in TICs versus Leydig cells cultures in anterior pituitary-grafted rats may be due to the influence of testicular interstitial macrophages. These observations correlate with in vivo conditions, where prolactin increases the release of TNF-alpha by testicular interstitial macrophages, which, in turn, decreases the human chorionic gonadotropin-stimulated release of testosterone by Leydig cells. In summary, hyperprolactinemia-induced hypogonadism involves a mechanism of prolactin-originated, macrophage-mediated inhibitory regulation of testosterone release by Leydig cells. TNF-alpha, one of the cytokines secreted by macrophages, may play a key role in this mechanism.

Number, distribution pattern, and identification of macrophages in the testes of infertile men

OBJECTIVE

To investigate the number, location, and secretory products of macrophages in human testes showing normal and abnormal spermatogenesis.

DESIGN

Evaluation of testicular biopsies with the use of immunohistochemistry, laser capture microdissection, and reverse transcriptase polymerase chain reaction.

SETTING

University research and clinical institutes.

PATIENT(S)

Infertile men with germ cell arrest (n = 10), Sertoli cell only (n = 8), or mixed atrophy (n = 7) syndromes, and with cases of idiopathic infertility showing normal spermatogenesis (n = 8).

INTERVENTION(S)

Diagnostic testicular biopsy was performed on participants.

MAIN OUTCOME MEASURE(S)

We recorded the location, number, distribution, and cytokine expression of human testicular macrophages.

RESULT(S)

CD68-positive macrophages were found in the testes of all groups analyzed. These macrophages expressed the genes for interleukin 1 and tumor necrosis factor-alpha, and were located in the interstitium, tubular wall, and tubular lumen. In Sertoli cell only and germ cell arrest syndromes, the overall macrophage number was increased over twofold. In all pathologic states, there was a significant shift of these cells from the interstitium to the tubules.

CONCLUSION(S)

Our study suggests that increased numbers of CD68-positive macrophages directly (via phagocytosis) or indirectly (via paracrine actions exerted through their secretory products) are involved in the regulation of steroidogenesis, Sertoli cell activity, germ cell survival, and, in consequence, in the pathogenesis or maintenance of infertility states in the human testes.

Human natural tumor necrosis factor alpha induces multiple endocrine and hematologic disorders in rats

Slc:Wistar male rats treated with human natural tumor necrosis factor alpha (hn TNF-alpha, 3 X 10(5) Japan reference units/kg intravenously) for 3 months showed histologic vacuolation of basophils in the anterior pituitary, hyperplasia of the thyroidal follicular epithelium, and hyperplasia of the testicular interstitial cells. The vacuolated basophils were immunohistochemically shown to be thyrotrophs. In addition, there were decreases in plasma levels of triiodothyronine (T3), thyroxin (T4), and testosterone, and an increase in thyroid-stimulating hormone (TSH). The number of lymphocytes in the marginal zones of lymphoid follicles in spleen and lymph nodes and B-lymphocytes in the peripheral blood decreased. Hyperplasia of hematopoietic cells in the bone marrow and decreases in both leukocytes and erythrocytes in the peripheral blood were prominent. Hyperplasia of bile ductular epithelial cells with periportal mononuclear cell infiltration in the liver and increased cellularity in alveolar walls in the lung were also characteristic. In in vitro studies, hn TNF-alpha inhibited both proliferation and peroxidase activity of thyroid follicular epithelial cells. These findings demonstrate that hn TNF-alpha may induce histologic vacuolation of thyrotrophs by causing a decrease in plasma levels of T3 and T4; hyperplasia of the thyroid follicular epithelium, which may be attributed to the increased plasma level of TSH; hyperplasia of testicular interstitial cells, by lowering the plasma level of testosterone; hyperplasia of bile ductular epithelial cells; hyperplasia of hematopoietic cells in bone marrow; and the increase in cellularity in pulmonary alveolar walls. In addition, hn TNF-alpha may suppress the differentiation of B-lymphocytes.

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.

Adaptive interactions between cytokines and the hypothalamic-pituitary-gonadal axis

Circulating and tissue concentrations of pyrogenic cytokines, especially interleukin (IL)-1 beta, vary temporally through the menstrual cycle and pregnancy. The secretion of these cytokines in vitro by isolated human mononuclear cells is significantly influenced by exogenous gonadal steroids and gonadotropins. Reciprocally, cytokines influence gonadotropin secretion by the pituitary and steroidogenesis by the ovaries and testes. Several hypotheses have been advanced regarding the adaptive value of these interrelationships. Cytokine-induced synthesis of proteolytic enzymes and extracellular matrix proteins may be important for the tissue remodeling necessary for ovulation, implantation, and delivery. Tolerance of the fetal allograft may require downregulation of cytotoxic effector cells and reciprocal upregulation of humoral and nonspecific host defenses. The inhibitory influence of IL-1 beta on the luteinizing hormone surge may prevent inopportune conception, and the abortive influences of tumor necrosis factor-alpha and gamma interferon may terminate pregnancy during periods of infection.

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.

Identification of IL-6 as one of the important cytokines responsible for the ability of mononuclear cells to stimulate Sertoli cell functions

There is increasing evidence that locally produced cytokines may play an important role in the control of testicular function. In a previous report we demonstrated that medium conditioned by activated human peripheral blood mononuclear cells (PBMC-CM), which is a rich source of cytokines, has extremely potent effects on Sertoli cell transferrin and cGMP secretion. Part of this activity could be explained by interleukin-1beta (IL-1beta) but additional cytokines were evidently involved. In the present study we tried to characterize and purify additional components active on Sertoli cells from PBMC-CM. To this end PBMC-CM was subjected to a purification procedure involving successively: adsorption to silicic acid, affinity chromatography with an antiserum recognizing a mixture of cytokines except IL-1beta, gel-filtration, reversed-phase HPLC and cation-exchange FPLC. Throughout this protocol a Sertoli cell bioassay was used to monitor the effects on transferrin and cGMP production. After cation-exchange FPLC, SDS-PAGE using silver staining showed a single protein band in the bioactive fractions. NH2-terminal amino-acid sequencing revealed that the active principle(s) in this band corresponded to four truncated forms of IL-6 missing the first 13, 14, 17 and 18 N-terminal amino-acids, respectively. The truncated IL-6 molecules were as active as intact IL-6 in the Sertoli cell bioassay. Since neither IL-1beta nor IL-6 alone or in combination could account for the extremely potent effect of PBMC-CM, we tested a series of additional cytokines (IL-1alpha, INF-alpha, IL-4, TGF-beta, IFN-gamma) alone and in combination with IL-1beta and IL-6. These data suggest that IL-1beta, IL-6 and TNF-alpha display more than additive effects on Sertoli cell transferrin and cGMP secretion and that the combination of these cytokines may explain the major part of the effects observed with crude PBMC-CM. The observation that the latter effects could be observed with murine as well as human IL-1beta, IL-6 and TNF-alpha further supports the potential physiological relevance of these findings.

Inhibition of gonadotropin-induced testosterone secretion by the intracerebroventricular injection of interleukin-1 beta in the male rat

The intracerebroventricular (icv) injection of the proinflammatory cytokine interleukin (IL)-1 beta is known to significantly decrease plasma LH levels in the male rat, thereby lowering testosterone (T) secretion. We show here that central administration of this cytokine (20-80 ng) also inhibits T secretion in response to human CG (hCG), an effect that is apparent already when IL-1 beta is injected 15 min before hCG. This phenomenon is independent of LH secretion because lowering LH levels with the potent GnRH antagonist Azaline B neither mimics nor affects the suppressive influence of icv IL-1 beta on the hCG-induced T secretory response. Elevations in plasma corticosterone levels do not seem to play a role either, because icv IL-1 beta is able to blunt hCG-induced T secretion in animals whose corticosterone has been removed by adrenalectomy or reduced by the administration of antibodies to CRF. Furthermore, the observation that icv IL-1 beta inhibits the T response to hCG before elevations in plasma IL-6 concentrations are detectable, and that central treatment with the cytokine is more effective than iv treatment, indicates that circulating levels of neither IL-1 beta nor IL-6 are important mediators of this effect. Collectively, these results lead us to propose that IL-1 beta of central origin influences neural pathways linking the brain and the testes, resulting in decreased testicular responses to hCG.

Recombinant murine tumor necrosis factor-alpha inhibits cholesterol side-chain cleavage cytochrome P450 and insulin-like growth factor-I gene expression in rat Leydig cells

The purpose of the present study was to evaluate the effects of murine recombinant tumor necrosis factor-alpha (TNF-alpha) on rat Leydig cell function. In primary cultures of Leydig cells, we found that in the presence of hCG (10 ng/ml), testosterone levels were markedly elevated, 69.3 +/- 3.1 ng/10(6) cells/h (mean + SE). TNF-alpha in a concentration of 1 ng/ml markedly inhibited testosterone biosynthesis (a 69% reduction; p < 0.01) and 100 ng/ml of TNF-alpha almost completely inhibited testosterone formation (p < 0.001). TNF-alpha (10 ng/ml) inhibited hCG (0.1, 1 and 10 ng/ml)-induced testosterone formation by 63%, 67% and 61%, respectively. TNF-alpha (10 ng/ml) also markedly inhibited 8-bromo cAMP-induced testosterone formation from 76 +/- 9 ng/10(6) cells/h to 4.9 ng/10(6) cells/h. This indicates that the major effect of TNF-alpha is at steps beyond LH receptor site. To further evaluate the site(s) of action of TNF-alpha, we evaluated its effect on the conversion of precursor steroids to testosterone. We found that the addition of 20-hydroxy-cholesterol could not reverse inhibitory effects of TNF-alpha on hCG-induced testosterone formation. TNF-alpha had no effect on the conversions of pregnenolone, 17-OH-pregnenolone, DHEA and androstenedione to testosterone. This indicates that the major effect of TNF-alpha is at the key steroidogenic enzyme, P450scc. We reported previously that human recombinant TNF-alpha had no effect on hCG-induced testosterone formation but did enhance the inhibitory effects of human recombinant IL-1beta. In the present study, we demonstrated that both murine TNF-alpha and human IL-1beta were potent inhibitors of hCG-induced testosterone formation. IL-1beta alone in concentrations of 0.1, 1 and 10 ng/ml inhibited testosterone formation by 45%, 62% and 91%, respectively, in the presence of TNF-alpha (10 ng/ml), IL-1beta in a concentration as low as 0.1 ng/ml completely blocked hCG-induced testosterone formation. We next evaluated the effect of TNF-alpha on P450scc gene expression. There was no constitutively expressed P450scc mRNA in Leydig cells after 24 h in culture. In response to hCG, there was a 33-fold increase in the P450scc mRNA level. Both TNF-alpha and IL-1beta inhibited hCG-induced expression of P450scc mRNA. Finally, the effect of TNF-alpha on IGF-I gene expression was investigated since IGF-I enhances Leydig cell androgen formation and IGF-I gene is expressed in high levels in Leydig cells. TNF-alpha inhibited both large (7.4 kb) and small species (0.8-1.2 kb) IGF-I mRNA levels in a dose-dependent manner. In conclusion, murine TNF-alpha is a potent inhibitor of Leydig cell function. TNF-alpha inhibited both P450scc and IGF-I mRNA gene expression.

Effects of tumor necrosis factor on the hypothalamic-pituitary-testicular axis in healthy men

Tumor necrosis factor (TNF) has been implicated as a mediator of many diseases associated with alterations in hypothalamic-pituitary-testicular (HPT) function. To assess the effects of TNF on the HPT axis, we performed a saline-controlled cross-over study in six healthy men, sequentially measuring serum concentrations of gonadotropins, testosterone, and sex hormone-binding globulin (SHBG) after a bolus intravenous injection of recombinant human TNF (50 micrograms/m2). TNF induced an early and transient increase in serum luteinizing hormone (LH) levels from 6.0 +/- 1.0 to a maximum of 8.0 +/- 1.0 U/L after 30 minutes (P < .005), whereas the concentrations of follicle-stimulating hormone (FSH) remained unchanged. The increase in LH concentrations was followed by a transient decrease in serum testosterone levels from 18.2 +/- 0.3 to 9.1 +/- 1.2 nmol/L after 4 hours (P < .0001). Remarkably, LH levels had returned to control values when the testosterone level reached its nadir. SHBG levels were not affected by TNF. Our results suggest that TNF affects the HPT axis at multiple levels and may be involved either directly or indirectly in the decrease in circulating testosterone concentrations in systemic illnesses.

Secretion of tumor necrosis factor alpha by testicular macrophages

While it has been shown that culture medium from testicular macrophages can influence testosterone production when added to Leydig cells, the identity of the factor(s) responsible for this activity remains unknown. Since tumor necrosis factor alpha (TNF alpha) has been shown to be capable of influencing testosterone production by Leydig cells, a series of studies was conducted to determine if testicular macrophages produce TNF alpha. It was found that testicular macrophages from adult rats produce a factor that is capable of lysing L929 cells, which are used as a traditional bioassay for TNF alpha. The TNF alpha activity in the macrophage-conditioned medium could be neutralized by the addition of anti-murine TNF alpha but not with the addition of preimmune IgG. While lipopolysaccharide (LPS) slightly increased the release of TNF alpha, neither follicle-stimulating hormone (FSH) nor testosterone had a similar effect. It was not determined if the isolation procedure had artificially 'activated' the macrophages. Medium from cultured Sertoli cells, Leydig cells and peritubular cells did not contain TNF alpha activity. These studies are consistent with the hypothesis that the paracrine interaction between testicular macrophages and Leydig cells is mediated in part by TNF alpha.

The role of cytokines in the regulation of Leydig cell P450c17 gene expression

Cytokines produced by immune-activated testicular interstitial macrophages (TIMs) may play a fundamental role in the local control mechanisms of testosterone biosynthesis in Leydig cells. We investigated whether in vivo immune-activation of TIMs can modulate Leydig cell steroidogenesis. To immune activate TIMs in vivo, mice were injected intraperitoneally (i.p.) with lipopolysaccharide (LPS, 6 mg/kg). TIMs and Leydig cells were purified for RNA analysis. LPS treatment resulted in a 47-fold increase in interleukin-1β (IL-1β) mRNA in TIMs. P450c17 mRNA levels in the Leydig cells from the same animals, decreased to less than 10% compared to control. The effect of LPS on IL-1β and P450c17 mRNA levels was reversible on both TIMs and Leydig cells, respectively. To determine if the effect of LPS on P450c17 was mediated by a possible decrease in pituitary LH secretion, mice were co-injected with LPS and hCG. Treatment with hCG did not change the effect observed with LPS alone, in TIMs or in Leydig cells. In vitro, LPS treatment of TIMs resulted in marked induction of IL-1β mRNA expression. In parallel, in vitro treatment of Leydig cells with recombinant IL-1 resulted in a dose-dependent inhibition of P450c17 mRNA expression and testosterone production. These data demonstrate that LPS treatment, in vivo and in vitro, induced IL-1 gene expression in TIMs, and that IL-1 inhibits P450c17 mRNA in vitro. Therefore, we suggest that immune-activation of TIMs might have caused the observed inhibition of P450c17 gene expression in Leydig cells in vivo.

Recombinant monocyte-derived interleukin-1 receptor antagonist reverses inhibitory effects of interleukin-1 on Leydig cell steroidogenesis

Previously we have reported that interleukin-1 (IL-1) is a potent inhibitor of Leydig cell function. Most recently, IL-1 receptor antagonist (IL-1ra) has been purified, sequenced and cloned. In the present study, we evaluated the recombinant monocyte-derived IL-1ra on the inhibitory effects of IL-1. The addition of recombinant human IL-1ra up to 1000 ng/ml has no discernible effects on human chorionic gonadotropin (hCG)-stimulated testosterone formation in primary cultures of rat Leydig cells. Similar to that reported previously, IL-1 beta caused a dose-dependent inhibition of hCG-induced testosterone. The inhibitory effect of IL-1 beta could be reversed by the concomitant addition of IL-1ra. The amounts of IL-1ra required to reverse the effect of IL-1 were 25-fold higher. Our results suggest that IL-1 is important in modulating Leydig cell function and its effect most likely is mediated by specific IL-1 receptors.