Functional and phenotypic characteristics of testicular macrophages in experimental autoimmune orchitis

Testicular inflammation with compromised fertility can occur despite the fact that the testis is considered an immunoprivileged organ. Testicular macrophages have been described as cells with an immunosuppressor profile, thus contributing to the immunoprivilege of the testis. Experimental autoimmune orchitis (EAO) is a model of organ-specific autoimmunity and testicular inflammation. EAO is characterized by an interstitial inflammatory mononuclear cell infiltration, damage of the seminiferous tubules and germ cell apoptosis. Here we studied the phenotype and functions of testicular macrophages during the development of EAO. By stereological analysis, we detected an increased number of resident (ED2+) and non-resident (ED1+) macrophages in the testicular interstitium of rats with orchitis. We showed that this increase was mainly due to monocyte recruitment. The in vivo administration of liposomes containing clodronate in rats undergoing EAO led to a reduction in the number of testicular macrophages, which correlated with a decreased incidence and severity of the testicular damage and suggests a pathogenic role of macrophages in EAO. By immunohistochemistry and flow cytometry we detected an increased number of testicular macrophages expressing MHC class II, CD80 and CD86 costimulatory molecules in rats with orchitis. Also, testicular macrophages from rats with EAO showed a higher production of IFNgamma (ELISA). We conclude that testicular macrophages participate in EAO development, and the ED1+ macrophage subset is the main pathogenic subpopulation. They stimulate the immune response through the production of pro-inflammatory cytokines and antigen presentation and thus activation of T cells in the target organ.

Testis structure and function in a nongenetic hyperadipose rat model at prepubertal and adult ages

There are few data for hormonal levels and testis structure and function during postnatal development in rats neonatally treated with monosodium L-glutamate (MSG). In our study, newborn male pups were ip injected with MSG (4 mg/g body weight) every 2 d up to 10 d of age and investigated at prepubertal and adult ages. Plasma levels of leptin, LH, FSH, prolactin, testosterone (T), corticosterone, and free T4 (FT4) were measured. MSG rats displayed elevated circulating levels of corticosterone and hyperadiposity/hyperleptinemia, regardless of the age examined; conversely, circulating prolactin levels were not affected. Moreover, prepubertal MSG rats revealed a significant (P < 0.05) reduction in testis weight and the number of Sertoli (SC) and Leydig cells per testis. Leptin plasma levels were severalfold higher (2.41 vs. 8.07; P < 0.05) in prepubertal MSG rats, and these animals displayed plasma LH, FSH, T, and FT4 levels significantly decreased (P < 0.05). Taken together, these data indicate that testis development, as well as SC and Leydig cell proliferation, were disturbed in prepubertal MSG rats. Adult MSG rats also displayed significantly higher leptin plasma levels (7.26 vs. 27.04; P < 0.05) and lower (P < 0.05) LH and FSH plasma levels. However, T and FT4 plasma levels were normal, and no apparent alterations were observed in testis structure of MSG rats. Only the number of SCs per testis was significantly (P < 0.05) reduced in the adult MSG rats. In conclusion, although early installed hyperadipose/hyperleptinemia phenotype was probably responsible for the reproductive axis damages in MSG animals, it remains to be investigated whether this condition is the main factor for hypothalamus-pituitary-gonadal axis dysfunction in MSG rats.

Direct effect of ghrelin on leptin production by cultured rat white adipocytes

OBJECTIVE

Because ghrelin is known to stimulate adipogenesis, we tested whether ghrelin could contribute to the maintenance of homeostasis, directly affecting rat white adipocyte leptin production.

RESEARCH METHODS AND PROCEDURES

Isolated retroperitoneal adipocytes were cultured for 0.5 to 48 hours without (baseline) or with (0.001 to 1 nM) ghrelin alone or in combination with insulin (0.01 to 10 nM) or dexamethasone (1 to 100 nM). Adipocytes were also incubated with ghrelin and inhibitors either of RNA (actinomycin D) or protein synthesis (cycloheximide) or with several concentrations (10 to 1000 nM) of a specific ghrelin antagonist. When cultures were terminated, we evaluated adipocyte leptin secretion and ob mRNA expression.

RESULTS

Our data indicate that ghrelin directly enhanced adipocyte leptin release and ob mRNA expression, that the leptin-releasing activity of ghrelin was additive to the action of both insulin and dexamethasone and was abrogated by protein synthesis inhibitors, and that effects of ghrelin on adipocyte ob mRNA expression and release were blocked by coincubation with the specific growth hormone secretagogue receptor 1a antagonist.

DISCUSSION

Our study supports the ability of ghrelin to enhance white adipose tissue leptin production by a direct receptor-mediated effect. This activity of ghrelin could play a potentially significant role in rapid restoration of homeostasis after food intake.

Modulatory effects of leptin on leydig cell function of normal and hyperleptinemic rats

Neonatal L-monosodium glutamate (MSG) administration in rats induces several neuroendocrine and metabolic disruptions. Leptin, the adipocyte product, modulates several neuroendocrine systems including the hypothalamic-pituitary-gonadal (HPG) axis in mammals. The aim of the present study was to determine whether MSG-induced chronic hyperleptinemia could play any relevant role in the hypogonadism developed by male rats when examined in adulthood. We found that 120-day-old MSG male rats displayed significant hyperleptinemia, hypogonadism, and undisturbed basic testis structure and spermatogenesis. In vitro studies in purified Leydig cells from normal (CTR) and MSG-damaged rats revealed that basal and human chorionic gonadotropin (hCG)-stimulated 17-hydroxy-progesterone (17-HO-P(4)), Delta(4)-androstenedione (Delta(4)A) and testosterone (T) secretions were significantly lower in MSG than in CTR cells. Exposure to murine leptin (Mleptin, 10(-8)M) significantly inhibited hCG-elicited T secretion by CTR cells after 180 min incubation. While Mleptin significantly inhibited hCG-stimulated Delta(4)A output and the Delta(4)A:17-OH-P(4) ratio of secretion, conversely, it failed to modify the ratio T:Delta(4)A release by CTR Leydig cells. Interestingly, the effects of Mleptin found on CTR Leydig cells were absent in MSG Leydig cells. Finally, endogenous hyperleptinemia was associated with a significant decrease in Leydig cell expression of Ob-Rb mRNA in MSG rats. In summary, this study demonstrates that: (1) Mleptin inhibited testicular steroidogenesis in CTR rats; (2) MSG-treated rats showed lower in vitro 17-OH-P(4), Delta(4)A and T production under basal and post-hCG stimulation conditions; (3) purified Leydig cells from MSG-treated rats displayed resistance to the inhibitory action of Mleptin on T release, and (4) endogenous leptin exerts a modulatory effect on Leydig cell Ob-Rb mRNA expression. The inhibitory effect of leptin on testicular function is thus abrogated in MSG-damaged rats. The testicular leptin-resistance developed by MSG rats seems to be due to early chronic exposure of Leydig cells to high leptin circulating levels, which in turn down-regulate testicular Ob-Rb expression. It remains to be determined whether the testicular dysfunction of MSG rats can be reversed after correction of hyperleptinemia or whether it is an irreversible effect of the hypothalamic lesion.

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.

Correlation between inhibin secretion and damage of seminiferous tubules in a model of experimental autoimmune orchitis

The aim of the present study was to evaluate inhibin secretion in rats with autoimmune orchitis. As we have previously described, experimental autoimmune orchitis (EAO) induced in rats by active immunization with testis homogenate and adjuvants is characterized by an interstitial mononuclear cell infiltrate and sloughing of the germinal epithelium. At 120 days after the first immunization 60% of the rats exhibited a severe orchitis with large areas of aspermatogenic seminiferous tubules in which only spermatogonia and Sertoli cells with cytoplasmic vacuolization remained attached to the tubular wall. None of the untreated (N) or control (C) rats revealed pathological alterations. Sixty percent decrease in testis weight was observed in rats with EAO compared with N or C groups. A 3-fold increase in serum FSH levels was observed in rats with EAO compared with N or C groups (19.8+/-3.7 vs 5.6+/-0.3 and 5.9+/-0.1 ng/ml respectively). A significant decrease in inhibin B levels was observed in rats with EAO when compared with N or C groups (40+/-4.6 vs 207+/-38.8 and 221.4+/-28.6 pg/ml respectively). An inverse correlation between inhibin B and FSH serum levels and a direct correlation between inhibin B and testis weight were found. Strong expression of the inhibin alpha-subunit in Sertoli cells of untreated and control rats was observed; this subunit was undetectable or poorly detectable in rats with orchitis. Positive staining for the inhibin alpha-subunit was also observed in Leydig cells of all groups studied. In conclusion, using a model of autoimmune orchitis our results show that circulating inhibin B levels and inhibin alpha-subunit expression in Sertoli cell cytoplasm closely correlate with the degree of damage of the germinal epithelium.

Effect of testicular macrophage conditioned media from rats with autoimmune orchitis on Leydig cell function

PROBLEM

The aim of this study was to investigate the influence of immune-activated testicular macrophages obtained from rats with autoimmune orchitis (EAO) on Leydig cell steroidogenesis.

METHOD OF STUDY

EAO was induced in rats by active immunization with testis homogenate and adjuvants. Testicular and peritoneal macrophages from rats with EAO were isolated and cultured for 24 hr. Testosterone (T) production by purified Leydig cells incubated in vitro with macrophage-conditioned media (CM) from rats with EAO or control rats was measured.

RESULTS

An increase in T production by Leydig cells incubated with CM from testicular, but not peritoneal, macrophages of rats with EAO was observed. This increase was dose-dependent up to a concentration of 30% CM; proportions higher than 35% exhibited an inhibitory effect.

CONCLUSIONS

Immune-activated testicular macrophages obtained from rats with EAO induced both stimulatory and inhibiting steroidogenic effects on Leydig cells in vitro and not the exclusively inhibitory action that has widely been attributed to activated macrophages. This dual effect probably depends on the ability of these cells to synthesize different molecules that may exert opposite effects.

Increased testosterone production in vitro by Leydig cells from rats with severe autoimmune orchitis

We have previously observed (M. O. Suescun et al., 1994, Journal of Andrology, 15, 442-448) that rats with autoimmune orchitis (EAO) exhibit increased testosterone production in vitro by isolated testes. The aim of the present study was to determine whether the increase in testosterone production correlated with an enhanced number of Leydig cells and/or enhanced steroidogenic capacity per Leydig cell. For this purpose, EAO was induced in adult Sprague-Dawley rats by active immunization with testicular homogenate and adjuvants. At 80 days after the primary immunization, 60% of rats presented with severe testicular damage characterized by sloughing of the seminiferous epithelium, seminiferous tubule atrophy and interstitial mononuclear cell infiltration. At 160 days after the first immunization, testicular lesions were more severe. A morphometric study, by light microscopy, showed an increase in the number of Leydig cells in rats with EAO (45% increase at 80 days and 50% at 160 days). By electronmicroscopy, testicular sections of rats with EAO revealed the presence of numerous Leydig cells closely associated with macrophages. Most Leydig cells exhibited ultrastructural features of active steroid secreting cells. The steroidogenic capacity of Percoll-purified Leydig cells from tests of rats with EAO, killed at 80 and 160 days, was evaluated. Leydig cells from rats with EAO exhibited an enhanced steroidogenic response to hCG in vitro at 80 days (38%) and an increase in basal (77%) and post-hCG testosterone production (115%) at 160 days compared to controls. However, these cells were less sensitive to hCG. In conclusion, the results indicate that the enhancement of in-vitro testosterone production observed in rats with EAO is accounted for both by the increased number of Leydig cells and by the increased testosterone production of each Leydig cell.

Polyamines in the male reproductive system

This review covers some common aspects of the biosynthesis, interconversion pathways and biochemical functions of polyamines. A particular emphasis is given in experimental models as well as humans, to their presence in the male gonad, prostate gland, seminal vesicles, epididymis and semen. The interaction between hormones (androgens, LH, FSH and PRL) and the main enzymes involved on the polyamine biosynthesis, and the relationship of these compounds on cell growth and differentiation, are also discussed. In this regard, an attention is offered to the potential role of polyamines during early spermatogenesis stages and the use of some enzymes involved in their biosynthesis as sensitive and specific markers of the action of androgens and antiandrogens in the epididymis. Finally, a special issue is addressed to the controversial information documented on polyamines, their oxidation products and the relationship with male fertility.

Alterations of testicular function after induced autoimmune orchitis in rats

The endocrinological profile of animals with experimental autoimmune orchitis (EAO) has not been sufficiently explored. With this purpose orchitis was induced in adult rats by active immunization with testicular homogenate (TH) and adjuvants. Animals were sacrificed 50 or 80 days after the first immunization. Forty-three percent of rats immunized with TH developed orchitis. Different degrees of cell sloughing and atrophy of the seminiferous tubules and numerous macrophages and lymphocytes in close association with Leydig cells were seen. A significant increase in the number of Leydig cells was observed in rats with orchitis killed at 50 and 80 days. An enhanced number of interstitial non-Leydig cells was also detected in rats with testicular damage killed at 80 days. Levels of serum follicle-stimulating hormone (FSH) were two- to threefold higher in rats with EAO compared to concentrations detected in other groups. Moreover, rats with orchitis had significantly increased testicular testosterone. Serum luteinizing hormone (LH) did not change in animals of any group. In vitro studies showed an increase in the basal and human chorionic gonadotropin (hCG)-stimulated testosterone production in rats with EAO. The increase in testicular steroidogenesis without a concomitant enhancement in serum LH levels detected in rats with autoimmune orchitis suggests the existence of local control mechanisms.

Modulation of ornithine decarboxylase activity by prolactin in seminal vesicles of the rat

The stimulatory effect of prolactin on sexual accessory glands is well established, though the mechanism of trophic action remains poorly understood. We have therefore assessed the effect of high levels of prolactin on ornithine decarboxylase activity and polyamine content in seminal vesicles (SV) of adult rats. Hyperprolactinaemia was induced by implantation of tissue fragments of a prolactin-secreting tumour 7315a, and the rats killed at 35 days post-inoculation. Serum levels of prolactin were increased significantly (p < 0.001) in tumour-bearing rats. Levels of testosterone in serum were reduced markedly, whereas LH levels remained unchanged. SV weight in the experimental group was not significantly different from that in the corresponding control group. A clear increase in ornithine decarboxylase activity of SV was observed (p < 0.001) in the hyperprolactinaemic rats. However, there was no change in the polyamine content of SV in tumour-bearing rats, compared to the control group. These results indicate that ornithine decarboxylase activity in SV of adult rats is regulated mainly by prolactin. This experimental model may be useful for identification of some of the events involved in the trophic action of prolactin.

Effects of gonadectomy and sex hormone therapy on the endotoxin-stimulated hypothalamo-pituitary-adrenal axis: evidence for a neuroendocrine-immunological sexual dimorphism

Bacterial lipopolysaccharide (LPS) stimulates the hypothalamo-pituitary-adrenal axis by a mechanism involving the release of cytokines, which activate the CRH-ACTH system and, as a result, increase glucocorticoid secretion. In the present study we investigated the possibility that endogenous sex hormones modulate the in vivo endotoxin-stimulated adrenal and immune responses in adult BALB/c mice. In preliminary experiments we determined that the maximal glucocorticoid release in response to LPS (50 micrograms, ip) administration was reached 2 h after treatment. The endotoxin effect on the adrenal and immune responses was then tested in male, randomly cycling female, 20-day-gonadectomized and 20-day-gonadectomized mice treated with either testosterone or estradiol. In addition, in vitro experiments were performed to determine whether 1) LPS exerts any direct effect on basal and ACTH-stimulated corticosterone release, and 2) adrenal function is influenced by bilateral gonadectomy and sex steroid therapy. Our results indicate that 1) randomly cycling female mice have significantly more pronounced corticosterone secretion than males 2 h after endotoxin injection, although the tumor necrosis factor responses were similar; 2) the response of the hypothalamo-pituitary-adrenal axis to endotoxin stimulation in female mice was invariable throughout the different stages of the normal estrous cycle; 3) gonadectomy leads to enhanced (P < 0.05) adrenal and immune responses to LPS stimulation compared to the responses in shams; 4) the endotoxin-elicited adrenal and immune overresponses observed in gonadectomized mice are reversed by testosterone treatment, regardless of sex; 5) LPS does not directly modify spontaneous and ACTH-stimulated adrenal corticosterone secretion; and 6) gonadectomy alone or combined with sex steroid therapy does not increase the in vitro adrenal response to ACTH stimulation. Our findings further suggest an evident neuroendocrine-immunological sexual dimorphism during the acute phase of inflammatory processes.

Effect of an antiestrogen on the testicular response to acute and chronic administration of hCG in normal and hypogonadotropic hypogonadic men: tamoxifen and testicular response to hCG

The effect of the antiestrogen tamoxifen (Tx) on the acute and chronic hCG administration was evaluated in patients with hypogonadotropic hypogonadism (HH) and in normal men. An hCG test (5000 IU hCG) was performed before, after two months of hCG administration (2000 IU hCG three times weekly) and after two months of hCG + Tx (2000 IU hCG three times weekly plus 20 mg/day of tamoxifen). Blood samples were obtained before and following 24 and 72 h of every test to determine T, E, 17OHP and SHBG. T increased only in HH with both treatments (X +/- SEM: Basal: 97.9 +/- 19.7; hCG: 237.7 +/- 43.2; hCG +/- Tx: 204.7 +/- 10.7 ng/100 ml). 17OHP rose with hCG alone, but not with hCG + Tx in both groups. E, SHBG and 17OHP/T ratio did not change after treatments. hCG tests: E increased 24 h following hCG administration in every test. The ratio 17OHP/T rose at 24 h in the first and second test but in the third test it did not change. These results support the role of E in the acute hCG-induced Leydig cell desensitization. However, the association of Tx does not improve T serum levels, suggesting that E might not be the unique factor involved in the mechanisms for testicular desensitization.

Ornithine decarboxylase activity as a marker of androgen and antiandrogen action in the rat epididymis

After castration, there was a marked decrease in serum androgen concentration at 6 h, and a dramatic inhibition of ornithine decarboxylase (ODC) at 12 h. Administration of testosterone propionate to castrated rats at a dose of 0.05 mg/animal restored ODC activity to the normal value. However, no change was observed when intact rats were treated with testosterone even at a 40-fold higher dose, indicating that endogenous androgens present in intact rats are far in excess for maintenance of maximal levels of activity. Administration of the antiandrogen flutamide to intact rats caused a moderate decrease in epididymal weight, whereas this effect was more pronounced in castrated, androgen-treated rats. In the latter, the effect of flutamide was significant at the lowest dose used (0.5 mg/day). ODC activity was significantly decreased by flutamide treatment of intact rats, but even at the highest dose used (10 mg/day) only a 39% inhibition was observed. In flutamide-treated rats, LH concentrations were markedly increased, as were serum and epididymal androgens. In androgen-treated castrated rats, flutamide caused epididymal ODC to fall to undetectable values. These results show that: (1) androgens are essential for the maintenance of ODC activity in the epididymis; (2) epididymal ODC activity is maximally stimulated by endogenous androgens, at least in the pubertal rat; (3) the apparent potency of flutamide is substantially lowered by an increase in epididymal androgens. We suggest that ODC is a sensitive marker of the action of androgens and antiandrogens in the epididymis.

Effects of induced hypoprolactinemia on testicular function during gonadal maturation in the rat

We have evaluated the effects of hypoprolactinemia during gonadal maturation in the male rat. Intact 30-day-old rats were injected daily for 10 days with three different doses of bromocriptine (0.75, 1.5 or 3.0 mg/kg of body weight/day). At the end of the treatment period, the animals were sacrificed, serum was collected for prolactin (PRL), LH, and androgen measurements. Intratesticular testosterone and 5 alpha-androstanediol (androstanediol) were measured following celite column chromatography and a specific radioimmunoassay. In addition, the production of androgens by decapsulated testes and dispersed Leydig cells was also studied in vitro. Serum levels of PRL (9.4 +/- 1.9 ng/ml) were suppressed to undetectable levels in the three bromocriptine-treated groups, whereas LH levels were not altered. All three doses of bromocriptine markedly depressed serum testosterone (plus DHT) and androstanediol. Intra-testicular testosterone and androstanediol were diminished (25% and 35%, respectively, P less than 0.05) during hypoprolactinemia. Decapsulated testes and dispersed Leydig cells from bromocriptine-treated animals showed a significant reduction in the basal secretion of testosterone (plus DHT) and androstanediol, and in androgen responses to submaximal hCG stimulation. Maximal steroidogenic responses from bromocriptine-treated rats were similar to controls. The present findings show that, during puberty, bromocriptine influences testicular steroidogenesis, and these effects may be partly due to changes in PRL levels. A direct effect of this dopaminergic agonist on the male gonad cannot be completely ruled out.

Induced hypoprolactinemia and testicular steroidogenesis in man

The effects of short-term hypoprolactinemia on the pituitary-gonadal axis were evaluated in a group of patients with untreated prostatic carcinoma. Each patient was studied prior to and during 7-day oral administrations of bromocriptine (2.5 mg q.i.d.). Serum LH, prolactin (PRL), androst-4-ene-3,17 dione (androstenedione), testosterone, and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha-Diol) levels, as well as intra-testicular testosterone, dihydrotestosterone (DHT), 5 alpha-Diol and zinc (Zn) concentrations, were determined. Daily administration of bromocriptine caused a marked suppression of serum PRL (mean +/- SEM, 23.8 +/- 2.5 vs. 6.4 +/- 1.0 ng/ml) without concomitant changes in serum LH levels (mean +/- SEM, 8.3 +/- 1.6 vs. 8.9 +/- 2.1 ng/ml). Hypoprolactinemia induced a significant decrease (P less than 0.05) in the mean peripheral testosterone levels; but 5 alpha-Diol and androstenedione remained unchanged. However, in testicular tissues, bromocriptine treatment resulted in significant increases in mean concentrations of total androgens (P less than 0.001), testosterone (P less than 0.001) and DHT (P less than 0.02). Testicular levels of 5 alpha-Diol were not significantly altered. There was no change in Zn levels in basal conditions and during bromocriptine administration. These results indicate that short-term suppression of serum PRL levels in man affects basal testicular function without altering serum LH. However, a direct action of bromocriptine on the human gonad cannot be excluded.

Testosterone, dihydrotestosterone, and zinc concentrations in human testis and epididymis

Tissue testosterone, dihydrotestosterone, and zinc concentrations have been determined in testis and epididymis of 13 patients with carcinoma of the prostate, 1 patient with carcinoma of the penis, and 3 patients with carcinoma of the prostate on estrogens. The 13 patients not receiving estrogens had the following testicular levels: testosterone, of 529 +/- 63.1 ng/g (mean +/- SE); dihydrotestosterone, 23.7 +/- 2.58 ng/g; and zinc 62.2 +/- 7.6 micrograms/g. The epididymal levels were as follows: testosterone, 40.6 +/- 3.4 ng/g; dihydrotestosterone, 20.5 +/- 2.36 ng/g; and zinc, 67.2 +/- 11.1 micrograms/g. Patients on estrogen therapy showed much lower androgen values in the two organs but zinc was not changed significantly. Concentrations of androgens were not significantly different in the epididymal fractions of caput, corpus, and cauda. In testis, there was a positive correlation between zinc and androgens contents, while the opposite was suggested by the data in the epididymis. Even though these patients were not normal, there was no evidence of testicular or epididymal disturbances.