The effect of testicular macrophages and interleukin-1 on testosterone production by purified adult rat Leydig cells cultured under in vitro maintenance conditions

Lower malathion concentrations reduce testosterone biosynthesis by Leydig TM3 cells in vitro by altering cellular redox profile and inducing oxidative damage

Malathion is an organophosphate pesticide used in agriculture and control of the Aedes aegypti mosquito. As previous reports have indicated the potential of malathion to compromise testosterone production in in vivo models, the objective of this study was to elucidate the mechanisms underlying the impairment of Leydig cell function, considering its critical role in male reproductive function. To this end, murine Leydig TM3 cells were exposed to concentrations of 1, 10, 100 or 1000 μM malathion for 24 h for evaluation of the compound on cell viability. Subsequently, concentrations of 1, 10, and 100 μM malathion were employed for a 24-h period to assess testosterone biosynthesis, levels of cytokines IL-1β, IL-6, IL-10, and TNF-α, as well as the redox profile. Malathion exerted a concentration-dependent impact on cell viability. Notably, the lower concentrations of malathion (1 and 10 μM) were found to impair testosterone biosynthesis in TM3 cells. While there were changes in IL-1 and TNF-α levels at specific concentrations, no direct correlation with altered hormone production was established. Our investigation revealed that varied malathion concentrations induced oxidative stress by increase in superoxide anion and a compensatory rise in antioxidants. In conclusion, the observed changes in the oxidative profile of TM3 cells were linked to functional impairment, evidenced by reduced testosterone biosynthesis at lower malathion concentrations.

In vitro effects of uncarboxylated osteocalcin on buffalo Leydig cell steroidogenesis

Uncarboxylated osteocalcin (UcOCN), a bone derived circulating protein, has been demonstrated to influence steroidogenesis in testicular Leydig cells of murine and human species. However, the role of UcOCN in testosterone biosynthesis remains unexplored in domestic animals. The present study aimed to investigate the impact of UcOCN on the expressions of steroidogenic genes (HSD3β1, HSD3β6, CYP17A1, CYP11A1), testosterone production and GPRC6A receptor localization in buffalo Leydig cells. Leydig cells from the testes of adult Murrah buffalo were isolated, with an average cell count and viability after digestion and Percoll enrichment of 1.43 × 106 cells/g of testes and 78.5%, respectively. Immunophenotyping of Percoll-enriched cell suspension by flow cytometry showed populations of Leydig cells ranging between 69 and 73.9%. Immunostaining confirmed the presence of GPRC6A receptors and CYP11A1 positive Leydig cells. When these cells were cultured and incubated with varying levels of UcOCN (6, 12, 24, and 48 ng/ml) and LH, there was a significant (P < 0.01) increase in testosterone production and up-regulation (P < 0.05) of CYP11A1, CYP17A1, HSD3β1 and HSD3β6 gene expression. In summary, the present study underscored the effects of UcOCN on testosterone biosynthesis, expression of crucial steroidogenic genes and interaction with GPRC6A receptors in buffalo Leydig cells, emphasizing its potential implications in andrology.

Testicular macrophages are recruited during a narrow fetal time window and promote organ-specific developmental functions

A growing body of evidence demonstrates that fetal-derived tissue-resident macrophages have developmental functions. It has been proposed that macrophages promote testicular functions, but which macrophage populations are involved is unclear. Previous studies showed that macrophages play critical roles in fetal testis morphogenesis and described two adult testicular macrophage populations, interstitial and peritubular. There has been debate regarding the hematopoietic origins of testicular macrophages and whether distinct macrophage populations promote specific testicular functions. Here our hematopoietic lineage-tracing studies in mice show that yolk-sac-derived macrophages comprise the earliest testicular macrophages, while fetal hematopoietic stem cells (HSCs) generate monocytes that colonize the gonad during a narrow time window in a Sertoli-cell-dependent manner and differentiate into adult testicular macrophages. Finally, we show that yolk-sac-derived versus HSC-derived macrophages have distinct functions during testis morphogenesis, while interstitial macrophages specifically promote adult Leydig cell steroidogenesis. Our findings provide insight into testicular macrophage origins and their tissue-specific roles.

Expression of CSF1, AR, and SRD5A2 during Postnatal Development of the Boar Reproductive Tract

Simple Summary

Understanding the initial development of the male reproductive system, including the prostate, should provide insight into malfunctions in the adult male. Although changes in circulating androgens during development are characterized in multiple species, potential changes in the androgen receptor, in the enzyme that converts testosterone to the presumably more potent dihydrotestosterone, and in colony stimulating factor 1, a critical mediator of macrophage influence on organ development, were previously unknown and anticipated to be influenced by androgens and estrogens. Gene expression in the testis, prostate, and seminal vesicles of these three mediators of development, including responses to reduced testosterone or estrogens, were evaluated. Each of these three genes had a unique temporal pattern of expression during postnatal reproductive tract development. However, surprisingly minimal effects of altered steroid signaling were reported on the expression of these presumed pivotal genes.

Abstract

The male reproductive system develops from a minimally functioning gonad and nonfunctioning accessory sex glands in the neonate; sex steroids, presumed to be primary influencers of these changes, have been characterized in multiple species. This study focused on the expression of the androgen receptor as the principal mediator of androgen-induced signaling; the 5α reductase enzyme that converts testosterone to the more active dihydrotestosterone; and colony stimulating factor 1, a mediator of macrophage influence on organ development in the pig. The time points chosen to evaluate normal developmental changes during the juvenile and prepubertal intervals included the inflection time points of 6.5 weeks of age at the nadir of circulating estradiol and testosterone concentrations in juveniles, and 11 weeks of age, when these concentrations begin to increase. The role of sex steroid signaling in the regulation of gene expression was evaluated by the blockade of androgen and estrogen receptors and reduction in endogenous estrogens. Expression of colony stimulating factor 1 in the testes gradually decreased during development; developmental profiles in the prostate and seminal vesicles were clearly different. Interference with sex steroid signaling had no effect on the expression of these three genes in testicular tissue and minimal and transient effects in prostate and seminal vesicles.

Immune Cells as Critical Regulators of Steroidogenesis in the Testis and Beyond

Steroidogenesis is an essential biological process for embryonic development, reproduction, and adult health. While specific glandular cells, such as Leydig cells in the testis, are traditionally known to be the principal players in steroid hormone production, there are other cell types that contribute to the process of steroidogenesis. In particular, immune cells are often an important component of the cellular niche that is required for the production of steroid hormones. For several decades, studies have reported that testicular macrophages and Leydig cells are intimately associated and exhibit a dependency on the other cell type for their proper development; however, the mechanisms that underlie the functional relationship between macrophages and Leydig cells are unclear. Beyond the testis, in certain instances immune cells themselves, such as certain types of lymphocytes, are capable of steroid hormone production, thus highlighting the complexity and diversity that underlie steroidogenesis. In this review we will describe how immune cells are critical regulators of steroidogenesis in the testis and in extra-glandular locations, as well as discuss how this area of research offers opportunities to uncover new insights into steroid hormone production.

The in vitro modulation of steroidogenesis by inflammatory cytokines and insulin in TM3 Leydig cells

BACKGROUND

Cytokines and hormones, including insulin, are known to modulate the hypothalamic-pituitary-testes axis and steroidogenesis, both centrally and peripherally. In the context of chronic inflammation and hyperinsulinaemia mediating male hypogonadism associated with obesity, metabolic syndrome and type 2 diabetes mellitus, these mechanisms are poorly understood and the impact of cytokines and insulin on Leydig cell steroidogenesis has not been fully elicited. This study aimed to further investigate the in vitro impact of TNFα, IL1ß, IL6, IL8 and insulin on Leydig cell function and steroidogenesis.

METHODS

hCG-stimulated TM3 Leydig cells were exposed to various concentrations of TNFα, IL1ß, IL6, IL8 (100 ng/ml, 10 ng/ml, 1 ng/ml and 0.1 ng/ml) and insulin (10 ng/ml, 1 ng/ml, 0.1 ng/ml and 0.01 ng/ml) in optimal cell culture conditions over 48 h. Cell viability (XTT) and testosterone and progesterone concentrations (ELISA) were assessed using standardised laboratory techniques.

RESULTS

TNFα significantly decreased cell viability and progesterone and testosterone concentrations in a dose-dependent relationship. IL1ß and IL6 had a subtle but significant negative effect on cell viability and testosterone concentrations, with a marked significant decrease in progesterone concentration at all concentrations investigated. IL8 showed an increase in cell viability, with no significant effect on testosterone concentrations alongside a significant decrease in progesterone concentrations. Insulin significantly increased cell viability and testosterone concentrations in a dose dependent relationship, but interestingly significantly decreased progesterone concentrations.

CONCLUSIONS

The inflammatory cytokines TNFα, IL1β and IL6 cause a dose dependent decline in steroidogenesis in TM3 Leydig cells. These results suggest that chronic inflammation may downregulate steroidogenesis in males via direct modulation of Leydig cell function. However, IL8 may stimulate TM3 Leydig cell growth. Insulin is associated with a dose-dependent increase in testosterone synthesis, with a significant decline in progesterone synthesis. With the phenomenon of insulin resistance, the literature is unclear on the potential role of hyperinsulinaemia in steroidogenesis. Further studies are warranted in order to fully elicit the molecular mechanisms and interactions of these molecules on male steroidogenesis.

Local Actions of Melatonin in Somatic Cells of the Testis

The pineal hormone melatonin regulates testicular function through the hypothalamic-adenohypophyseal axis. In addition, direct actions of melatonin in somatic cells of the testis have been described. Melatonin acts as a local modulator of the endocrine activity in Leydig cells. In Sertoli cells, melatonin influences cellular growth, proliferation, energy metabolism and the oxidation state, and consequently may regulate spermatogenesis. These data pinpoint melatonin as a key player in the regulation of testicular physiology (i.e., steroidogenesis, spermatogenesis) mostly in seasonal breeders. In patients with idiopathic infertility, melatonin exerts anti-proliferative and anti-inflammatory effects on testicular macrophages, and provides protective effects against oxidative stress in testicular mast cells. Consequently, melatonin is also involved in the modulation of inflammatory and oxidant/anti-oxidant states in testicular pathology. Overall, the literature data indicate that melatonin has important effects on testicular function and male reproduction.

Inhibition of NOS-NO System Prevents Autoimmune Orchitis Development in Rats: Relevance of NO Released by Testicular Macrophages in Germ Cell Apoptosis and Testosterone Secretion

Background

Although the testis is considered an immunoprivileged organ it can orchestrate immune responses against pathological insults such as infection and trauma. Experimental autoimmune orchitis (EAO) is a model of chronic inflammation whose main histopathological features it shares with human orchitis. In EAO an increased number of macrophages infiltrate the interstitium concomitantly with progressive germ cell degeneration and impaired steroidogenesis. Up-regulation of nitric oxide (NO)-NO synthase (NOS) system occurs, macrophages being the main producers of NO.

Objective

The aim of our study was to evaluate the role of NO-NOS system in orchitis development and determine the involvement of NO released by testicular macrophages on germ cell apoptosis and testosterone secretion.

Method and Results

EAO was induced in rats by immunization with testicular homogenate and adjuvants (E group) and a group of untreated normal rats (N) was also studied. Blockage of NOS by i.p. injection of E rats with a competitive inhibitor of NOS, L-NAME (8mg/kg), significantly reduced the incidence and severity of orchitis and lowered testicular nitrite content. L-NAME reduced germ cell apoptosis and restored intratesticular testosterone levels, without variations in serum LH. Co-culture of N testicular fragments with testicular macrophages obtained from EAO rats significantly increased germ cell apoptosis and testosterone secretion, whereas addition of L-NAME lowered both effects and reduced nitrite content. Incubation of testicular fragments from N rats with a NO donor DETA-NOnoate (DETA-NO) induced germ cell apoptosis through external and internal apoptotic pathways, an effect prevented by N-acetyl-L-cysteine (NAC). DETA-NO inhibited testosterone released from Leydig cells, whereas NAC (from 2.5 to 15 mM) did not prevent this effect.

Conclusions

We demonstrated that NO-NOS system is involved in the impairment of testicular function in orchitis. NO secreted mainly by testicular macrophages could promote oxidative stress inducing ST damage and interfering in Leydig cell function.

Melatonin in testes of infertile men: evidence for anti-proliferative and anti-oxidant effects on local macrophage and mast cell populations

Melatonin acting through the hypothalamus and pituitary regulates testicular function. In addition, direct actions of melatonin at the testicular level have been recently suggested. We have described that melatonin inhibits androgen production in hamster Leydig cells via melatonin subtype 1a (mel1a) receptors and the local corticotrophin-releasing hormone (CRH) system. The initial events of the melatonin/CRH signalling pathway have also been established. Melatonin and all components of the melatonergic/CRH system were also detected in Leydig cells of infertile men. This study attempted to search for additional targets of melatonin in the human testis, and to investigate the effects of melatonin on proliferation and the oxidative state in these novel target cells. To this aim, evaluation of human testicular biopsies of patients suffering from hypospermatogenesis or Sertoli cell only syndrome and cell culture studies were performed. Melatonergic receptors were found in macrophages (MACs) and mast cells (MCs) of the human testis. In biopsies of patients suffering idiopathic infertility, melatonin testicular concentrations were negatively correlated with MAC number per mm(2) and TNFα, IL1β and COX2 expression, but positively correlated with the expression of the anti-oxidant enzymes SOD1, peroxiredoxin 1 and catalase. Melatonin inhibited proliferation and the expression of pro-inflammatory cytokines and cyclooxygenase 2 (COX2) in both the human non-testicular THP-1 MAC cell line and primary cell cultures of hamster testicular MACs. In the human HMC-1 MC line, melatonin increased the expression of anti-oxidant enzymes and decreased reactive oxygen species (ROS) generation. The results reveal new testicular targets of melatonin and describe anti-proliferative and anti-inflammatory effects of this hormone on testicular MACs. Furthermore, melatonin might provide protective effects against oxidative stress in testicular MCs.

Distinct expression of interleukin-1α, interleukin-1β, and interleukin-1 receptor antagonist in testicular tissues and cells from human biopsies with normal and abnormal histology

Cytokines are paracrine/autocrine growth factors known to affect testicular cell functions. The cellular origin and expression levels of interleukin-1 (IL-1) in human normal and pathological testicular biopsies are not yet clear. In the present study, we have investigated the levels and cellular origin of IL-1 family members [IL-1α, IL-β, and IL-1 receptor antagonist (IL-1ra)] in human testicular normal and abnormal biopsies with incomplete maturation arrest (IMA) or Sertoli only syndrome (SOS), using real-time polymerase chain reaction and immunohistochemical staining analysis. Our results show that the levels of IL-1α were higher in Leydig/interstitial cells of biopsies with IMA and SOS compared with normal. The levels of IL-1α in Sertoli cells of normal biopsies were higher than IMA and SOS. The mRNA levels of IL-1α were similar in all biopsies. IL-1β levels were higher in Leydig/interstitial cells of normal biopsies compared with Sertoli and germ cells. The levels of IL-1β were similar in testicular cells of all biopsies. However, the mRNA levels of IL-1β were significantly lower in SOS and IMA biopsies compared with normal. IL-1ra was expressed only in Leydig/interstitial cells, and their expression in normal biopsies was higher than in biopsies with IMA and SOS. The mRNA levels of IL-1ra were similar in all biopsies. Thus, it is possible to suggest the involvement of IL-1 system in the regulation of spermatogenesis and male infertility.

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.

Possible involvement of microglia containing cyclooxygenase-1 in the accumulation of gonadotrophin-releasing hormone in the preoptic area in female rats

Prostaglandins (PGs), especially PGE(2), are involved in the hypothalamic control of gonadotrophin-releasing hormone (GnRH) release, acting at least in part on the terminal of GnRH axons in the median eminence. The present study aimed: (i) to clarify the role of PG(s) in regulating GnRH cell function at the level of the perikarya in the preoptic area; (ii) to determine the cyclooxygenase (COX) isozyme responsible for producing PG(s) that regulates GnRH perikarya; and (iii) to identify cell types that contain the responsible COX isozyme in female rats. A surge of luteinising hormone (LH) secretion was induced by oestrogen and progesterone in ovariectomised rats. Treatment of the rat before the LH surge with indomethacin, a nonselective COX inhibitor, or NS-398, a selective COX-2 inhibitor, did not interfere with the surge. However, treatment with indomethacin or flurbiprofen, a selective COX-1 inhibitor, significantly reduced the number of GnRH-immunoreactive cells in the preoptic area at the time of peak LH secretion during the surge. NS-398 did not affect the GnRH immunoreactivity. Double-labelled immunofluorescent histochemistry revealed COX-1 immunoreactivity in the vicinity of, but not within, GnRH containing neurones in the preoptic area. COX-2 immunoreactivity was not found in the same area. The COX-1 immunoreactivity was almost entirely localised in microglia in the preoptic area, but not in neurones or astrocytes. These results suggest that microglia in the preoptic area containing COX-1 are responsible for producing PG(s), which, in turn, facilitates the accumulation of GnRH during the gonadotrophin surge in female rats.

Constitutive expression of prostaglandin-endoperoxide synthase 2 by somatic and spermatogenic cells is responsible for prostaglandin E2 production in the adult rat testis

Prostaglandins (PGs), particularly PGE(2), have been implicated in the control of testicular steroidogenesis, spermatogenesis, and local immunity. However, virtually nothing is known about the expression or activity of the prostaglandin-endoperoxide synthases (PTGSs; also referred to as the cyclooxygenases), the specific rate-limiting enzymes responsible for PG production, in the adult testis. This activity was investigated in rats under normal conditions and during lipopolysaccharide-induced inflammation using quantitative real-time PCR, in situ hybridization, Western blotting, and PGE(2) measurements by ELISA. The mRNA for both the "constitutive" Ptgs1 and the "inducible" Ptgs2 forms was detected in multiple testicular cell types. Testicular Ptgs2 expression was substantially higher than that of Ptgs1, and testicular production of PGE(2) in vitro was found to be suppressed by a specific PTGS2 inhibitor (NS-398), but not by an inhibitor of PTGS1. Further investigation indicated that 1) PGE(2) production in the adult testis is attributable to constitutive expression of PTGS2 by somatic (Leydig cells and Sertoli cells) and spermatogenic cells; 2) testicular macrophages constitutively produce relatively low levels of PTGS2 and PGE(2) but are the only cell type to respond significantly to an inflammatory stimulus by increasing production of PGE(2); and 3) testicular PTGS2 expression and intratesticular PGE(2) levels are only marginally affected by acute inflammation. These data point toward a previously unanticipated maintenance role for the "inducible" PTGS2 enzyme in normal testicular function, as well as an anomalous response of testicular PTGS2 to inflammatory stimuli. Both observations are consistent with the reduced capacity of the testis to initiate and support inflammatory reactions.

Paracrine modulation of androgen synthesis in rat leydig cells by nitric oxide

The free radical nitric oxide (NO), generated through the oxidation of L-arginine to L-citrulline by NO synthases (NOSs), has been shown to inhibit steroidogenic pathways. NOS isoforms are known to be present in rat and human testes. Our study examined the sensitivity of Leydig cells to NO and determined whether NOS activity resides in Leydig cells or in another cell type such as the testicular macrophage. The results showed a low level of L-[14C]arginine conversion in purified rat Leydig cell homogenates. Administration of the NOS inhibitor L-N(G)-nitro-arginine methyl ester (L-NAME), or the calcium chelator ethylenebis (oxyethylenenitrilo)tetraacetic acid (EGTA), had no effect on L-[14C]citrulline accumulation. Increased intracellular Ca2+ concentrations that were induced by a calcium ionophore, or the addition of luteinizing hormone (LH), failed to affect NO formation in intact cells that were cultured in vitro. Introduction of a high concentration of the NO precursor L-arginine did not decrease testosterone (T) production, and NOS inhibitors did not increase T biosynthesis. However, exposing Leydig cells to low concentrations of the NO donor S-nitrosoglutathione (GSNO) induced a dramatic blockade of T production under basal and LH-stimulated conditions. DNA array assays showed a low level of expression of endothelial NOS (eNOS), while the neuronal and inducible isoforms of NOS (nNOS and iNOS) were below detection levels. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses confirmed these findings and demonstrated the presence of high iNOS messenger RNA (mRNA) levels in activated testicular macrophages that produced large amounts of NO. These data suggest that, while T production in rat Leydig cells is highly sensitive to NO and an endogenous NO-generating system is not present in these cells, NOS activity is more likely to reside in activated testicular macrophages.

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.

Modulation of goldfish testicular testosterone production in vitro by tumor necrosis factor alpha, interleukin-1beta, and macrophage conditioned media

The relevance of immune-endocrine interactions to the regulation of testicular steroidogenesis in teleosts is virtually unexplored. The objectives of the present study were: 1) to investigate the effects of murine cytokines, tumor necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta), and trout (Oncorhynchus mykiss) macrophage conditioned media (MCM) on testosterone (T) production by goldfish (Carassius auratus) testis pieces in vitro; and 2) to identify the site(s) of the inhibitory action of TNFalpha on hCG-stimulated T formation. TNFalpha (0-100 ng/ml) affected basal T production differentially depending on the gonadosomatic index (GSI) value of the fish. TNFalpha stimulated basal T of fish with a relatively low GSI (average 1.99), but inhibited T production by testis of fish with a higher GSI (average 5.14). The remaining studies used fish with only high GSI values. IL-1beta (0-10 ng/ml) inhibited basal T production, while MCM (0-25% v/v) had no effect. The cytokines significantly inhibited hCG-stimulated T production at all doses tested, whereas MCM was inhibitory only at the lower doses of 2.5-5% v/v. TNFalpha did not affect basal or hCG-stimulated cAMP levels, but did inhibit forskolin (0.5 microM; adenylate cyclase activator) and 8-bromo-cAMP (0.15 mM; cAMP analog) stimulated T levels. The inhibitory actions of TNFalpha on T production were greatly reduced by treatment of testis with 25-hydroxycholesterol (1 and 10 microg/ml), pregnenolone (50 and 100 ng/ml), and 17 alpha-hydroxypregesterone (50 ng/ml). TNFalpha caused a moderate decrease in pregnenolone (100 ng/ml)-stimulated T production. Together, these data demonstrate that regulatory actions of TNFalpha may occur at multiple sites within the steroid biosynthetic pathway, but the major effect appears to be related to cholesterol availability in the mitochondria. In conclusion, the results of this study implicate macrophage-derived factors in the regulation of teleost testicular androgen biosynthesis.

Is steroid deficiency the cause of tolerance in nitrate therapy?

The award of the Nobel Prize in Physiology and Medicine for 1998 bears witness to the 'explosive' field of nitric oxide (NO), and who would have thought the explosive nitroglycerin owed its therapeutic effectiveness to this little molecule? NO is also involved in causing penile erection, which has brought sildenafil to the aid of patients with erectile dysfunction. However, emerging evidence in animals and in vitro studies indicates that NO also inhibits steroidogenesis, which may have repercussions in humans. The decrease in androgen secretion may impact on secondary sexual characteristics, including penile size. The tolerance to the nitrate therapy in angina, characterized by volume expansion and not due to sodium retention, may also be related to steroid hormone deficiency. Decreased cortisol secretion may impair water excretion, resulting in volume expansion. Impaired aldosterone secretion would cause hyponatraemia with resultant raised renin. I hypothesize that continuous therapy with nitrates and sildenafil will result in diminished levels of steroid hormones with predicted sequelae.

D-Aspartate stimulation of testosterone synthesis in rat Leydig cells

D-Aspartate increases human chorionic gonadotropin-induced testosterone production in purified rat Leydig cells. L-Aspartate, D-,L-glutamate or D-,L-asparagine could not substitute for D-aspartate and this effect was independent of glutamate receptor activation. Testosterone production was enhanced only in cells cultured with D-aspartate for more than 3 h. The increased production of testosterone was well correlated with the amounts of D-aspartate incorporated into the Leydig cells, and L-cysteine sulfinic acid, an inhibitor of D-aspartate uptake, suppressed both testosterone production and intracellular D-aspartate levels. D-Aspartate therefore is presumably taken up into cells to increase steroidogenesis. Intracellular D-aspartate probably acts on cholesterol translocation into the inner mitochondrial membrane, the rate-limiting process in steroidogenesis.

Testicular Pathologic Changes and the Pituitary-Testicular Axis During Human Immunodeficiency Virus Infection

OBJECTIVE

To chronicle pituitary-testicular axis dysfunction and its clinicopathologic features in homosexual men.

METHODS

Between 1984 and 1992, 84 homosexual men underwent longitudinal follow-up for 4 years. At entry into the study, 28 were seronegative and 56 were seropositive for human immunodeficiency virus (HIV). Although 40 subjects remained asymptomatic (nonprogressors), 16 had progression to acquired immunodeficiency syndrome (AIDS). Of those 16 patients with progression, 8 had AIDS within 2 years (early progressors) and 8 demonstrated AIDS within 4 years after enrollment (late progressors), and all died. The testes of five patients were examined at autopsy. The control group had similar follow-up. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, and bioavailable testosterone (bio-T) were measured in stored sera collected at 2-year intervals. The last hormonal measurement was between 3 and 24 months before autopsy. Comparison was made between autopsied and nonautopsied patients with AIDS as well as between HIV nonprogressors and control seronegative men. The correlation between pathologic findings and hormonal status was examined by regression analysis.

RESULTS

At baseline, testosterone, bio-T, LH, and FSH were not significantly different among all patients and subjects. During the study period, testosterone, bio-T, and serum gonadotropin levels remained unchanged in the seronegative homosexual men. In nonprogressors, serum FSH and LH concentrations remained unchanged, whereas testosterone and bio-T levels decreased significantly during this 4-year period. After progression to AIDS (in both groups of progressors), the serum FSH and LH levels were higher and the serum testosterone and bio-T were lower in comparison with values in the seronegative men. In late progressors to AIDS, FSH and LH increased, whereas serum testosterone and bio-T decreased significantly from baseline. All five patients with AIDS on whom autopsy was done had boundary wall thickening of the seminiferous tubules and decreased spermatogenesis. No significant differences were found in serum testosterone, bio-T, and LH between those in whom autopsy was or was not done; however, FSH was significantly higher in the autopsied cases. The serum testosterone and bio-T levels were negatively correlated with the interstitial inflammation. A significant correlation was also observed between change of bio-T and weight loss.

CONCLUSION

We conclude that dysfunction of the pituitary-gonadal axis is common in HIV-infected men. All patients in whom autopsy was done because of AIDS-related diseases had been hypogonadal 3 to 24 months before death. Decreased spermatogenesis, subacute interstitial inflammation, or both were seen at autopsy of patients with AIDS. Pathologic damage to the testes during AIDS was associated with decreased testosterone and bio-T as well as increased serum gonadotropin levels. In a substantial proportion of men with progression to AIDS, compensated hypogonadism (normal serum testosterone and increased serum LH levels) preceded the development of low serum testosterone level.

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.

The role of cyclic AMP production, calcium channel activation and enzyme activities in the inhibition of testosterone secretion by amphetamine

1. The aim of this study was to investigate the mechanism by which amphetamine exerts its inhibitory effect on testicular interstitial cells of male rats. 2. Administration of amphetamine (10(-12)-10(-6) M) in vitro resulted in a dose-dependent inhibition of both basal and human chorionic gonadotropin (hCG, 0.05 iu ml(-1))-stimulated release of testosterone. 3. Amphetamine (10(-9) M) enhanced the basal and hCG-increased levels of adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation in vitro (P<0.05) in rat testicular interstitial cells. 4. Administration of SQ22536, an adenylyl cyclase inhibitor, decreased the basal release (P<0.05) of testosterone in vitro and abolished the inhibitory effect of amphetamine. 5. Nifedipine (10(-6) M) alone decreased the secretion of testosterone (P<0.01) but it failed to modify the inhibitory action of amphetamine (10(-10)-10(-6) M). 6. Amphetamine (10(-10)-10(-6) M) significantly (P<0.05 or P<0.01) decreased the activities of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), P450c17, and 17-ketosteroid reductase (17-KSR) as indicated by thin-layer chromatography. (t.l.c.). 7. These results suggest that increased cyclic AMP production, decreased Ca2+ channel activity and decreased activities of 3beta-HSD, P450c17, and 17-KSR are involved in the inhibition of testosterone production induced by the administration of amphetamine.

Expression of stem cell factor in the postnatal rat testis

The expression of stem cell factor (SCF) mRNA and protein was examined in the postnatal rat testis. Northern blot analysis of total RNA from 1-4 days postpartum (dpp) testes showed none or barely detectable levels of the approximately 6.5 kb SCF transcript. At 5 dpp, there was a striking elevation in this mRNA, a timing that coincides with the onset of spermatogonial proliferation. Immunohistochemical staining of testes showed that SCF protein was readily detected within Sertoli cells at 1-7 dpp and in the adult. Immunoreactive material was also detected within gonocytes and within Leydig cells at 1-7 dpp and in Leydig cells in the adult. Given the intense staining of Leydig cells by two different antibodies to SCF, the potential synthesis of SCF mRNA by these cells was investigated. Northern blot and reverse transcription/polymerase chain reaction analysis indicated that adult Leydig cells do not synthesize SCF mRNA, and Sertoli cells do. The significance of these findings is discussed in the context of germ cell-Sertoli cell interactions and Leydig cell function.

Bacterial lipopolysaccharide (LPS) and interleukin 1 (IL-1) exert multiple physiological effects in the tilapia Oreochromis mossambicus (Teleostei)

To gain insight in immuno-endocrine communication in teleosts the physiological effects of interleukin 1 and bacterial lipopolysaccharide in teleosts were investigated. Tilapia (Oreochromis mossambicus) were treated with murine interleukin 1 and E. coli lipopolysaccharide in vivo, and lipopolysaccharide was administered to pituitary lobes and head kidneys in vitro. The integument of the fish appeared to be a sensitive target for the preparations tested, since proliferation of chloride cells and of epidermal mucous cells was observed as well as an increase in epidermal thickness. These effects may relate to an acute phase-like reaction caused by the treatments. Lipopolysaccharide administration furthermore resulted in an increase in plasma free fatty acids levels. Lipopolysaccharide, but not interleukin 1, stimulated the interrenal axis of the fish, as judged by the increase in cortisol production measured in superfusion of head kidneys. In addition to these in vivo effects, lipopolysaccharide also displayed several effects in vitro. Pituitary adrenocorticotropic hormone, as well as alpha-melanocyte stimulating hormone, release was inhibited, and the head kidney responsiveness to adrenocorticotropic hormone was inhibited after pretreatment of the tissue with the E. coli product. This latter effect coincided with the release of an unidentified alpha-melanocyte stimulating hormone immunoreactive fraction by the head kidneys which could be stimulated by lipopolysaccharide. The data strongly support the notion that the immune system is involved in adaptive regulations in teleosts, and that immunoendocrine interactions are phylogenetically old mechanisms.

The effects of interleukin 1 beta on the hypothalamic tachykinin, neurokinin A

Interleukin-1 beta (IL-1 beta) is a pleiotropic cytokine that appears to be an integral component of the bidirectional signalling between the immune and central nervous systems. It is produced in the hypothalamus and has been shown to inhibit the hypothalamo-pituitary-gonadal axis and to activate the hypothalamo-pituitary-adrenal axis. IL-1 beta is reported to up-regulate the tachykinin, substance P (SP), in the peripheral nervous system. We have recently observed that members of the hypothalamic tachykinin family including SP, neurokinin A (NKA) and two N-terminal extended forms of NKA (neuropeptides kappa and gamma), inhibit hypothalamic LHRH and pituitary LH release and stimulate adrenal corticosterone secretion. The similarity in the endocrine effects of the tachykinins and the cytokine prompted us to test the hypothesis that IL-1 beta may stimulate the hypothalamic tachykinins, which would then mediate the neuroendocrine effects of IL-1 beta. First, the effects of IL-1 beta on the in vitro release of NKA-like immunoreactivity (NKA-li) from the hypothalamus was examined. Addition of 10 nM IL-1 beta significantly increased NKA-li release from the hypothalami of castrated rats, but not from the hypothalami of intact rats. To identify the site of IL-1 beta action, the effects of intraventricular IL-1 beta (100 ng) on NKA-li levels in various hypothalamic sites of intact and castrated rats were examined. The results showed that IL-1 beta increased NKA-li selectively in the median eminence (ME) and arcuate nucleus (ARC) of castrated rats only.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of receptor tyrosine kinases in the rat testis

Evidence of receptor/ligand interactions that regulate testis cell function was sought in order to broaden the current understanding of the molecular basis of testis cell function. Using reverse transcription and the polymerase chain reaction, we have obtained novel evidence for the expression of three mRNAs encoding receptor tyrosine kinases in the adult rat testis: the platelet-derived growth factor type A receptor (PDGF-RA), the basic fibroblast growth factor receptor (flg), and fetal liver kinase 1 (Flk-1). A 6.8 kb transcript encoding the PDGF-RA was observed in RNA prepared from testes of rats aged day 5 through adult, with a decline in relative abundance with increasing age after day 17. Analysis of mRNA from isolated cell preparations (day 21 Sertoli cells, adult Leydig cells, round spermatids, and primary spermatocytes) and testes depleted of specific cell types [ethane dimethane sulfonate (EDS)-treated and cryptorchid] indicated that the Leydig cell was the predominant source of this mRNA in the adult testis. The addition of PDGF-BB to cultures of highly purified adult rat Leydig cell preparations resulted in a 40% increase in LH-stimulated testosterone production, confirming a role for this growth factor in regulation of Leydig cell function. These data indicate that the Leydig cell is a principal site of action of PDGF in the testis.