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

Acute effects of para-chloroamphetamine on testosterone and markers of apoptosis in seminiferous epithelium of prepubertal male rats

Serotonin is a neurotransmitter that affects the secretion of gonadotropins and testosterone. In prepubertal male rats, serotonin has a stimulating role in testosterone secretion. Here, we used prepubertal male rats to study the effects of para-chloroamphetamine (pCA) on circulating testosterone and gonadotropins and markers of apoptosis in germ cells from day 1 to day 5 post-treatment. The intraperitoneal administration of pCA induced a significant reduction in concentrations of hypothalamic serotonin and circulating testosterone, but gonadotropins were not affected. In the seminiferous epithelium of pCA-treated rats, increased the number of germ cells positive to markers of apoptosis, concomitantly with alterations in morphometry and the presence of multinucleated germ cells. Levels of testosterone were reduced starting from 1 day after pCA was administered. The time window between the administration of the pCA and collection of samples was sufficient to detect changes in testosterone levels, in contrast with a previous work where no changes were found. There was a possible relationship between the reduction of testosterone and an increase in the number of germ cells positive to apoptosis markers. However, the mechanism that links pCA-testosterone-germ cell positive to markers of apoptosis is unknown. Our outcomes support the view that pCA exposure during the prepubertal stage has an acute impact on testosterone levels and affects the structure and physiology of seminiferous epithelium.

Sex difference in the interrelationship between TNF-α and oxidative stress status in first-episode drug-naïve schizophrenia

Background

Increasing evidence indicates that dysregulated TNF-α and oxidative stress (OxS) contribute to the pathophysiology of schizophrenia. Additionally, previous evidence has demonstrated sex differences in many aspects of schizophrenia including clinical characteristics, cytokines, and OxS markers. However, to the best of our knowledge, there is no study investigating sex differences in the association between TNF-α, the OxS system, and their interaction with clinical symptoms in schizophrenia patients, especially in first-episode drug-naïve (FEDN) patients.

Methods

A total of 119 FEDN schizophrenia patients and 135 healthy controls were recruited for this study. Serum TNF-α, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA) were measured. The Positive and Negative Syndrome Scale (PANSS) was applied to evaluate psychotic symptoms. Two-way ANOVA, partial correlation analysis, and multivariate regression analysis were performed.

Results

A sex difference in MDA levels was demonstrated only in healthy controls (F = 7.06, p_Bonferroni = 0.045) and not seen in patients. Furthermore, only male patients had higher MDA levels than male controls (F = 8.19, p_Bonferroni = 0.03). Additionally, sex differences were observed in the association of TNF-α and MDA levels with psychotic symptoms (all p_Bonferroni < 0.05). The interaction of TNF-α and MDA was only associated with general psychopathology symptom in male patients (B = − 0.07, p = 0.02).

Conclusion

Our results demonstrate the sex difference in the relationship between TNF-α, MDA, and their interaction with psychopathological symptoms of patients with schizophrenia.

Amphetamine-Decreased Progesterone and Estradiol Release in Rat Granulosa Cells: The Regulatory Role of cAMP- and Ca2+-Mediated Signaling Pathways

The purpose of this study is to evaluate the amphetamine effects on progesterone and estradiol production in rat granulosa cells and the underlying cellular regulatory mechanisms. Freshly dispersed rat granulosa cells were cultured with various test drugs in the presence of amphetamine, and the estradiol/progesterone production and the cytosolic cAMP level were measured. Additionally, the cytosolic-free Ca²⁺ concentrations ([Ca²⁺]i) were measured to examine the role of Ca²⁺ influx in the presence of amphetamine. Amphetamine in vitro inhibited both basal and porcine follicle-stimulating hormone-stimulated estradiol/progesterone release, and amphetamine significantly decreased steroidogenic enzyme activities. Adding 8-Bromo-cAMP did not recover the inhibitory effects of amphetamine on progesterone and estradiol release. H89 significantly decreased progesterone and estradiol basal release but failed to enhance a further amphetamine inhibitory effect. Amphetamine was capable of further suppressing the release of estradiol release under the presence of nifedipine. Pretreatment with the amphetamine for 2 h decreased the basal [Ca²⁺]i and prostaglandin F2α-stimulated increase of [Ca²⁺]i. Amphetamine inhibits progesterone and estradiol secretion in rat granulosa cells through a mechanism involving decreased PKA-downstream steroidogenic enzyme activity and L-type Ca²⁺ channels. Our current findings show that it is necessary to study the possibility of amphetamine perturbing reproduction in females.

Testicular STAC3 regulates Leydig cell steroidogenesis through potentiating mitochondrial membrane potential and StAR processing

SH3 and cysteine-rich protein 3 (STAC3), a small adapter protein originally identified as a core component of excitation–contraction coupling machinery, regulates the voltage-induced Ca²⁺ release in skeletal muscle. However, the possibility of additional, as yet unknown, non-muscle effects of STAC3 cannot be ruled out. Herein, we provide the evidence for the expression and functional involvement of STAC3 in spermatogenesis. STAC3 expression was localized in the testicular interstitium of rodent and human testes. By using the cytotoxic drug ethylene dimethane sulfonate (EDS), STAC3 expression was observed to be decreased sharply in rat testis after selective withdrawal of Leydig cells (LCs), and reappeared immediately after LCs repopulation, indicating that testicular expression of STAC3 mainly stems from LCs. From a functional standpoint, in vivo lentiviral vector–mediated suppression of STAC3 resulted in a significant decrease in testosterone production, and thereafter caused impairment of male fertility by inducing oligozoospermia and asthenospermia. The indispensible involvement of STAC3 in testicular steroidogenesis was validated using the in vivo knockdown model with isolated primary LCs as well as in vitro experiments with primary LCs. By generating the TM3^Stac3−/− cells, we further revealed that STAC3 depletion attenuated mitochondrial membrane potential and StAR processing in db-cAMP-stimulated LCs. Thus, the inhibitory effect of STAC3 deficiency on testicular steroidogenesis may be ascribed to a disturbed mitochondrial homeostasis. Collectively, the present results strongly suggest that STAC3 may function as a novel regulator linking mitochondrial homeostasis and testicular steroidogenesis in LCs. Our data underscore an unexpected reproductive facet of this muscle-derived factor.

Substance Abuse and Male Hypogonadism

Progressive deterioration of male reproductive function is occurring in Western countries. Environmental factors and unhealthy lifestyles have been implicated in the decline of testosterone levels and sperm production observed in the last fifty years. Among unhealthy lifestyles, substance and drug abuse is a recognized cause of possible alterations of steroidogenesis and spermatogenesis. Alcohol, opioids and anabolic-androgenic steroids are capable to reduce testosterone production in male interfering with testicular and/or hypothalamic-pituitary function. Other substances such as nicotine, cannabis, and amphetamines alter spermatogenesis inducing oxidative stress and subsequent apoptosis in testicular tissue. Substance and drug abuse is a potentially reversible cause of hypogonadism, defined as the failure of the testis to produce physiological concentrations of testosterone and/or a normal number of spermatozoa. The identification of the abuse is important because the withdrawal of substance intake can reverse the clinical syndrome. This review summarizes the most important clinical and experimental evidence on the effect of substance abuse on testosterone and sperm production.

Impaired serotonin communication during juvenile development in rats diminishes adult sperm quality

Spermatogenesis and steroidogenesis are testicular functions regulated by gonadotrophins as well as other factors, including serotonin. Testicular serotonin acts as an autocrine regulator of testosterone secretion, but studies on its role in spermatogenesis and sperm quality are scarce. Here, we analyzed the effects of intratesticular inhibition of serotonin synthesis on gonadotrophins, testosterone, and sperm quality. Both testicles of 30-day-old rats were injected once with saline solution (SS) or distinct concentrations of p-chloroamphetamine (PCA) (0.03, 0.06, or 0.12 mg). At 65 days of age, rats were euthanized and sperm density, motility, membrane integrity, mitochondrial function, and abnormalities were evaluated in gametes from the vas deferens. Inhibition of synthesis of intratesticular serotonin by PCA diminished the concentrations of testosterone and follicle-stimulating hormone (FSH) but luteinizing hormone (LH) levels were unaltered. Sperm density was not modified in animals injected with the different concentrations of PCA. In contrast, the percentage of sperm with abnormalities increased and the sperm membrane integrity decreased in animals injected at higher PCA concentrations. The functionality of sperm mitochondria in PCA-injected animals decreased only at the highest PCA dose. Our results indicate that testicular serotonin plays a role in testosterone synthesis and in the normal development of sperm, and blocking its effects disrupts the hormonal communication between the testis and hypophysis.

ABBREVIATIONS

SS: saline solution; PCA: p-chloroamphetamine; FSH: follicle-stimulating hormone; LH: luteinizing hormone; TPH: tryptophan hydroxylase; MAO: monoamine oxidase; AC: absolute control group; PI: propidium iodide; FLICA: fluorescence inhibitor of caspase; 3β-HSD: 3β-hydroxysteroid dehydrogenase; 17-KSR: 17-ketosteroid reductase; DHT: 5-dihydrotestosterone.

Prepubertal male rats with high rates of germ-cell apoptosis present exacerbated rates of germ-cell apoptosis after serotonin depletion

Male germ-cell apoptosis occurs naturally and can be increased by exposure to drugs and toxic chemicals. Individuals may have different rates of apoptosis and are likely to also exhibit differential sensitivity to outside influences. Previously, we reported that p-chloroamphetamine (pCA), a substance that inhibits serotonin synthesis, induced germ-cell apoptosis in prepubertal male rats. Here, we identified prepubertal rats with naturally high or low rates of germ-cell apoptosis and evaluated gene expression in both groups. Bax and Shbg mRNA levels were higher in rats with high rates of germ-cell apoptosis. Rats were then treated with pCA and the neuro-hormonal response and gene expression were evaluated. Treatment with pCA induced a reduction in serotonin concentrations but levels of sex hormones and gonadotrophins were not changed. Rats with initially high rates of germ-cell apoptosis had even higher rates of germ-cell apoptosis after treatment with pCA. In rats with high rates of germ-cell apoptosis Bax mRNA expression remained high after treatment with pCA. On the basis of category, an inverse relationship between mRNA expression of Bax and Bcl2, Bax and AR and Bax and Hsd3b2 was found. Here we provide evidence that innate levels of germ-cell apoptosis could be explained by the level of mRNA expression of genes involved with apoptosis and spermatogenesis.

Eurycomanone, the major quassinoid in Eurycoma longifolia root extract increases spermatogenesis by inhibiting the activity of phosphodiesterase and aromatase in steroidogenesis

ETHNOPHARMACOLOGICAL RELEVANCE

Eurycoma longifolia Jack (Simaroubaceae family), known locally as 'Tongkat Ali' by the ethnic population, is popularly taken as a traditional remedy to improve the male libido, sexual prowess and fertility. Presently, many tea, coffee and carbonated beverages, pre-mixed with the root extract are available commercially for the improvement of general health and labido. Eurycomanone, the highest concentrated quassinoid in the root extract of E. longifolia improved fertility by increasing testosterone and spermatogenesis of rats through the hypothalamus-pituitary-gonadal axis, but the mechanisms underlying the effects are not totally clear.

AIM OF THE STUDY

To provide evidences on the plant ethnopharmacological use and the involvement of eurycomanone, the major indigenous plant quassinoid in testosterone steroidogenesis and spermatogenesis increase.

MATERIAL AND METHODS

The rat testicular Leydig cell-rich interstitial cells were isolated and incubated in the culture medium M199. The viability of the cells was determined with trypan blue staining and the concentration of the viable cells was counted with a haemocytometer. The 3β-hydroxysteroid dehydrogenase (HSD) staining method was used to measure the abundance of Leydig cells in the preparation. Eurycomanone and the standard steroidogenesis inhibitors were incubated with 1.0 × 10(5) cells, and after 2h, the testosterone and the oestrogen concentrations were determined by the ELISA method. Computational molecular docking was performed to determine the binding affinity of the compound at the respective steroidogenesis enzymes.

RESULTS

Eurycomanone (EN) significantly increased testosterone production dose-dependently at 0.1, 1.0 and 10.0 μM (P<0.05), but the two lower doses when combined with 3-isobutyl-1-methylxanthine (IBMX), the phosphodiesterase inhibitor were not significantly higher than EN or IBMX alone, except at a higher concentration. The molecular docking studies indicated EN and IBMX were binding at different sites of the enzyme. EN has no reversal of inhibition by aminoglutethimide, ketoconazole or nifedipine at the respective steroidogenesis enzyme. The quassinoid was also non-responsive to the inhibition of oestrogen receptor by tamoxifen, but displayed improved formestane inhibition of aromatase in reducing oestrogen production. The molecular docking studies further supported that EN and formestane bound to aromatase with similar orientations and free energy binding values.

CONCLUSION

Eurycomanone enhanced testosterone steroidogenesis at the Leydig cells by inhibiting aromatase conversion of testosterone to oestrogen, and at a high concentration may also involve phosphodiesterase inhibition. The quassinoid may be worthy for further development as a phytomedicine to treat testosterone-deficient idiopathic male infertility and sterility.

Standardized quassinoid-rich Eurycoma longifolia extract improved spermatogenesis and fertility in male rats via the hypothalamic-pituitary-gonadal axis

ETHNOPHARMACOLOGICAL RELEVANCE

Eurycoma longifolia Jack, a small Simaroubaceae tree, known locally as 'Tongkat Ali' is popularly used as a sexual tonic in traditional medicine for aphrodisiac activity and improvement of fertility and male libido.

AIM OF THE STUDY

To investigate the effects of the standardized bioactive fraction of E. longifolia and its chemical constituents on the male fertility and the mechanisms of action involved.

MATERIAL AND METHODS

The powdered roots of E. longifolia were extracted separately with methanol and water. The organic extract upon further fractionation on HP 20 resin and elution with the methanol/water mixture afforded four fractions (F1-F4). These fractions, together with the crude aqueous (W) and organic extracts were standardized following their respective major quassinoid content and profile. The effects of the fractions on the rat spermatogenesis were compared with that of the aqueous extract (W) to determine the bioactive fraction. The effects of the bioactive fraction on the sperm count and quality, the histological morphometric changes on the spermatogenesis cycle, fertility and hormonal changes of plasma testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH) and estrogen in the animals upon oral administration were determined. The effects of the bioactive quassinoids on the testosterone release from the isolated testicular interstitial cells rich in Leydig cells, were also described.

RESULTS

The male rats orally administered with 25mg/kg of F2 and 250mg/kg of W, significantly increased the sperm concentration when compared with that of the control animals (P<0.05). High performance liquid chromatography analysis revealed that 25mg/kg of F2 and 250mg/kg of W were almost similar in concentration of eurycomanone, the major and most potent quassinoid. Microscopic morphometrical analysis of the rat testis following treatment with F2, showed significant increase in the number of spermatocytes and round spermatids at Stage VII of the spermatogenesis cycle when compared to that of the control (P<0.05). The estimated spermatozoa production rate and the number of Leydig cells were also elevated (P<0.001). The fertility index, fecundity index and the pup litter size delivered from the females after mating with the males treated with F2 were increased. The plasma testosterone level of the animals given 25mg/kg of F2 orally was significantly different at day-26 (p<0.05) and day-52 (P<0.01) from those of control but was not different at day-104. The testicular testosterone also peaked in the animals treated with 25mg/kg F2 and was higher than that in the plasma. The plasma LH and FSH levels of the rats treated with 25mg/kg of F2 were higher than those of the control (P<0.001). In contrast, the plasma estrogen level was significantly lower than that of the untreated control. Amongst the isolated quassinoids of F2, eurycomanone and 13α(21)-dihydroeurycomaone significantly increased the testosterone level from the Leydig cells of the testicular interstitial cells cultured in vitro (P<0.05).

CONCLUSION

The standardised extract F2 of E. longifolia and its major quassinoids especially eurycomanone improved the rat spermatogenesis by affecting the hypothalamic-pituitary-gonadal axis and the potential efficacy may be worthy of further investigation.

Differential effects of nonylphenol on testosterone secretion in rat Leydig cells

Nonylphenol (NP), a final metabolite of nonylphenol polyethoxylate, has been reported to interfere with male reproduction. However, its mechanisms are not fully understood. In the present study, we examined the effects of NP on steroidogenesis of testosterone in rat Leydig cells. The testosterone concentrations in rat plasma were examined after intravenous injection of NP (100 microg/kg) at different time intervals. In addition, rat Leydig cells were challenged with different concentrations of NP (4.25-127.5 microM) to evaluate its influences on testosterone steroidogenesis. Administration of NP showed a decrease of hCG-induced plasma testosterone. Moreover, in vitro experiments revealed that NP (127.5 microM) alone stimulated testosterone release through increase of both protein levels and activities of the StAR and P450(SCC). In contrast, NP inhibited hCG-induced testosterone release in rat Leydig cells. The inhibitory effect was also observed after incubation of the Leydig cells in the presence of different precursors. These results suggested that NP had differential effects on testosterone synthesis.

Detection of calretinin expression in abnormal immature Sertoli cells in non-obstructive azoospermia

The current study identified for the first time calretinin expression in abnormal Sertoli cells of azoospermic men who underwent testicular biopsy for sperm recovery and application of the retrieved sperm by in vitro fertilization techniques. Testicular biopsies with various spermatogenic impairments were evaluated immunohistochemically for the expression of the calretinin calcium-binding protein and the marker for immaturity of Sertoli cells, cytokeratin-18 (CK-18). Distribution of the markers was assessed in testes demonstrating a histological phenotype of mixed atrophy, Sertoli cell-only, or normal spermatogenesis (obstructive-azoospermia) and in men carrying a deletion in the azoospermia factor region located on the Y chromosome. Calretinin-immunopositive immature Sertoli cells revealed by co-localization of both markers, calretinin and CK-18, were identified in the mixed atrophy group in seminiferous tubules demonstrating spermatogenic failure. Sertoli cells expressing both markers were rarely detected in all other groups. Leydig cells in all the assessed biopsies expressed calretinin and served as a built-in control for immunoreactivity. This pattern of calretinin-selective expression in immature Sertoli cells suggests a functional relationship between calretinin expression and the degree of Sertoli cell differentiation. Disorders of Sertoli cell differentiation as indicated by calretinin and/or CK-18 expression contribute to the multifactorial mechanisms underlying spermatogenic failure.

Molecular biology of the 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase gene family

The 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) isoenzymes are responsible for the oxidation and isomerization of Delta(5)-3beta-hydroxysteroid precursors into Delta(4)-ketosteroids, thus catalyzing an essential step in the formation of all classes of active steroid hormones. In humans, expression of the type I isoenzyme accounts for the 3beta-HSD activity found in placenta and peripheral tissues, whereas the type II 3beta-HSD isoenzyme is predominantly expressed in the adrenal gland, ovary, and testis, and its deficiency is responsible for a rare form of congenital adrenal hyperplasia. Phylogeny analyses of the 3beta-HSD gene family strongly suggest that the need for different 3beta-HSD genes occurred very late in mammals, with subsequent evolution in a similar manner in other lineages. Therefore, to a large extent, the 3beta-HSD gene family should have evolved to facilitate differential patterns of tissue- and cell-specific expression and regulation involving multiple signal transduction pathways, which are activated by several growth factors, steroids, and cytokines. Recent studies indicate that HSD3B2 gene regulation involves the orphan nuclear receptors steroidogenic factor-1 and dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Other findings suggest a potential regulatory role for STAT5 and STAT6 in transcriptional activation of HSD3B2 promoter. It was shown that epidermal growth factor (EGF) requires intact STAT5; on the other hand IL-4 induces HSD3B1 gene expression, along with IL-13, through STAT 6 activation. However, evidence suggests that multiple signal transduction pathways are involved in IL-4 mediated HSD3B1 gene expression. Indeed, a better understanding of the transcriptional factors responsible for the fine control of 3beta-HSD gene expression may provide insight into mechanisms involved in the functional cooperation between STATs and nuclear receptors as well as their potential interaction with other signaling transduction pathways such as GATA proteins. Finally, the elucidation of the molecular basis of 3beta-HSD deficiency has highlighted the fact that mutations in the HSD3B2 gene can result in a wide spectrum of molecular repercussions, which are associated with the different phenotypic manifestations of classical 3beta-HSD deficiency and also provide valuable information concerning the structure-function relationships of the 3beta-HSD superfamily. Furthermore, several recent studies using type I and type II purified enzymes have elegantly further characterized structure-function relationships responsible for kinetic differences and coenzyme specificity.

Antisteroidogenic actions of hydrogen peroxide on rat Leydig cells

It has been well known that reactive oxygen species (ROS) are produced in the steroidogenic pathway and spermatozoa. H2O2, one of ROS produced by spermatozoa, appears to be a primary toxic agent. In the present study, we examined the effects of H2O2 on the basal and evoked-testosterone release from primary Leydig cells, the protein expressions of cytochrome P450 side chain cleavage enzyme (P450scc) and steroidogenic acute regulatory (StAR) protein were also investigated. Our preparation was found to contain approximately 87% Leydig cells and very few macrophages. The results demonstrated that H2O2 (>1 x 10(-4) M) significantly inhibited the basal and hCG-stimulated testosterone release. H2O2 abolished forskolin- or 8-Br-cAMP-evoked testosterone release. In the presence of pregnenolone, progesterone, or androstenedione, the inhibitory effect of H2O2 on testosterone release was prevented. H2O2 also inhibited pregnenolone production in the presence of trilostane (an inhibitor of 3beta-hydroxysteroid dehydrogenase), therefore diminished the activity of P450scc in Leydig cells. In addition to the inhibition of hormone secretion, H2O2 also regulated steroidogenesis by diminishing protein expression of StAR. These results suggest that H2O2 acts directly on rat Leydig cells to diminish testosterone production by inhibiting P450scc activity and StAR protein expression.

Effects of amphetamine on steroidogenesis in MA-10 mouse Leydig tumor cells

Amphetamine influences plasma and testicular testosterone levels. However, there is no evidence that amphetamine can directly influence Leydig cell functions. In the present study, a MA-10 mouse Leydig tumor cell line was used to determine whether and how amphetamine affected Leydig cell steroidogenesis. MA-10 cells were treated with different concentrations of amphetamine without or with human chorionic gonadotropin (hCG) and/or enzyme precursors over different time durations. Steroid production, enzyme activities and StAR protein expression were determined. Amphetamine alone had no any effect on MA-10 cell steroidogenesis. However, amphetamine (10(-11)M and 10(-10)M) significantly enhanced hCG-treated progesterone production at 3 hr in MA-10 cells (p < 0.05). Furthermore, amphetamine significantly induced more progesterone production upon treatment with 22R-hydroxycholesterol (p < 0.05), a precursor of P450 side-chain cleavage enzyme (P450scc). However, amphetamine did not induce more progesterone production when treated with pregnenolone (p > 0.05), a precursor of 3beta-hydroxysteroid dehydrogenase. In addition, the expressions of StAR protein and P450scc enzyme were not significantly different between hCG alone and hCG plus amphetamine treatment in MA-10 cells (p > 0.05). These results suggested that amphetamine enhanced hCG-induced progesterone production in MA-10 cells by increasing P450scc activity without influencing StAR protein and P450scc enzyme expression or 3beta-HSD enzyme activity.

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.

Progesterone attenuates the inhibitory effects of cardiotonic digitalis on pregnenolone production in rat luteal cells

Previous studies have shown that digoxin decreases testosterone secretion in testicular interstitial cells. However, the effect of digoxin on progesterone secretion in luteal cells is unclear. Progesterone is known as an endogenous digoxin-like hormone (EDLH). This study investigates how digitalis affected progesterone production and whether progesterone antagonized the effects of digitalis. Digoxin or digitoxin, but not ouabain, decreased the basal and human chorionic gonadotropin (hCG)-stimulated progesterone secretion as well as the activity of cytochrome P450 side chain cleavage enzyme (P450scc) in luteal cells. 8-Br-cAMP and forskolin did not affect the reduction. Neither the amount of P450scc, the amount of steroidogenic acute regulatory (StAR) protein, nor the activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) was affected by digoxin or digitoxin. Moreover, in testicular interstitial and luteal cells, progesterone partially attenuated the reduction of pregnenolone by digoxin or digitoxin and the progesterone antagonist, RU486, blocked this attenuation. These new findings indicated that (1) digoxin or digitoxin inhibited pregnenolone production by decreasing the activity of P450scc enzyme, but not Na(+)-K(+)-ATPase, resulting in a decrease on progesterone secretion in rat luteal cells, and (2) the inhibitory effect on pregnenolone production by digoxin or digitoxin was reversed partially by progesterone. In conclusion, digoxin or digitoxin decreased progesterone production via the inhibition of pregnenolone by decreasing P450scc activity. Progesterone, an EDLH, could antagonize the effects of digoxin or digitoxin in luteal cells.

Cutaneous androgen metabolism: basic research and clinical perspectives

The skin, especially the pilosebaceous unit composed of sebaceous glands and hair follicles, can synthesize androgens de novo from cholesterol or by locally converting circulating weaker androgens to more potent ones. As in other classical steroidogenic organs, the same six major enzyme systems are involved in cutaneous androgen metabolism, namely steroid sulfatase, 3beta-hydroxy-steroid dehydrogenase, 17beta-hydroxysteroid dehydrogenase, steroid 5alpha-reductase, 3alpha-hydroxysteroid dehydrogenase, and aromatase. Steroid sulfatase, together with P450 side chain cleavage enzyme and P450 17-hydroxylase, was found to reside in the cytoplasm of sebocytes and keratinocytes. Strong steroid sulfatase immunoreactivity was observed in the lesional skin but not in unaffected skin of acne patients. 3beta-hydroxysteroid dehydrogenase has been mainly immunolocalized to sebaceous glands, with the type 1 being the key cutaneous isoenzyme. The type 2 17beta-hydroxysteroid dehydrogenase isoenzyme predominates in sebaceous glands and exhibits greater reductive activity in glands from facial areas compared with acne nonprone areas. In hair follicles, 17beta-hydroxysteroid dehydrogenase was identified mainly in outer root sheath cells. The type 1 5alpha-reductase mainly occurs in the sebaceous glands, whereby the type II isoenzyme seems to be localized in the hair follicles. 3alpha-hydroxysteroid dehydrogenase converts dihydrotestosterone to 3alpha-androstanediol, and the use of 3alpha-androstanediol glucuronide serum level to reflect the hyperandrogenic state in hirsute women may be a reliable parameter, especially for idiopathic hirsutism. In acne patients it is still controversial if 3alpha-androstanediol glucuronide or androsterone glucuronide could serve as suitable serum markers for measuring androgenicity. Aromatase, localized to sebaceous glands and to both outer as well as inner root sheath cells of anagen terminal hair follicles, may play a "detoxifying" role by removing excess androgens. Pharmacologic development of more potent specific isoenzyme antagonists may lead to better clinical treatment or even prevention of androgen-dependent dermatoses.

Expression of calretinin in human ovary, testis, and ovarian sex cord-stromal tumors

Calretinin, a calcium-binding protein, is primarily expressed in certain subtypes of neurons. It has also been found to be present in mesothelial cells and mesotheliomas but not in many types of carcinomas. Using a polyclonal anti-calretinin antibody, we investigated the expression of calretinin immunohistochemically in nonneoplastic human ovaries and testes and ovarian sex cord-stromal tumors (SCSTs). In ovaries, calretinin was expressed in theca interna cells, hilus cells, and scattered individual stromal cells. Oocytes, granulosa cells, theca externa cells, rete ovarii, and most stromal cells were negative. Expression of calretinin was also seen in the ovarian surface epithelium and in collapsed and flat epithelial inclusion glands (EIGs), but not in round, columnar, and ciliated EIGs. In some glands, a transition from calretinin-positive to calretinin-negative epithelium was observed. In postpubertal testes, calretinin was expressed in Leydig cells, but not in germ cells or most rete testes and Sertoli cells. In ovarian SCSTs, strong calretinin staining was seen in all hilus cell tumors (4/4) and the Leydig cell component of Sertoli-Leydig cell tumors (10/10). The Sertoli cell component showed focal weak positivity in 5/10. Fibrothecomas were completely negative (0/8). In granulosa cell tumors, the tumor cells were either completely negative (8/14) or weakly positive at the periphery of the tumor (6/14) while scattered stromal cell staining was seen in 9/14 cases. The expression of calretinin in normal Leydig cells, theca interna cells, the Leydig cell component of Sertoli-Leydig cell tumors, and hilus cell tumors suggests its functional relationship with androgen production. Its pattern of expression in ovarian SCSTs is useful in the differential diagnosis of these tumors. The presence of a transition from calretinin-positive, flat, nonciliated epithelium to calretinin-negative, columnar, ciliated epithelium in the same glands provides strong evidence for mullerian metaplasia.

Effects of hyperprolactinemia on testosterone production in rat Leydig cells

The pathogenesis of hyperprolactinemia (hyperPRL) induced hypogonadism has been suggested to be related with a dysfunction of hypothalamus-pituitary-testis axis. While the direct inhibitory effects of prolactin (PRL) on testosterone (T) release have been demonstrated, the mechanism is still unclear. Our previous study demonstrated a diminished T release in the testicular interstitial cells (TICs) from the anterior pituitary (AP)-grafted rats as compared with the control, and the pattern was in agreement with the in vivo model. However, TICs incubation cannot totally represent the response of the Leydig cells. Therefore, a Percoll gradient purified Leydig cell model was adopted to explore the response of T release under similar challenges in this study to investigate the effects of hyperPRL on the Leydig cells per se. HyperPRL in male rats was induced by grafting rat AP under the renal capsule. The control animals were grafted with rat brain cortex tissue (CX). Six weeks after grafting, the rats were sacrificed. Either TICs or Leydig cells were isolated, respectively, for in vitro incubation and challenge. Challenge drugs included human chorionic gonadotropin (hCG, 0.05 IU/ml), steroidogenic precursors (25-OH-cholesterol, 10(-6) M; pregnenolone, 10(-6) M), forskolin (an anenylyl cyclase activator, 10(-4) M) and 8-bromo-3':5' cyclic adenosine monophosphate (cAMP) (8-Br-cAMP 10(-4) M). T released by TICs or Leydig cells was determined by radioimmunoassay. The TICs from the AP-grafted rats showed lower levels of T release than the control group while the purified Leydig cells demonstrated a reverse pattern in response to challenges of hCG, steroidogenic precursors, forskolin and 8-Br-cAMP. In hyperPRL rats, a paradoxical pattern of T release between TICs and purified Leydig cells is observed. The purified Leydig cells from AP-grafted rats demonstrated a higher level amount of T release than the control after stimulation. The phenomenon can be attributed to the change of Leydig cell sensitivity to the stimulation after the effects of chronic hyperPRL. Moreover, another possibility is the role played by other interstitial cells to modulate steroidogenesis in Leydig cells.

Direct effects of propylthiouracil on testosterone secretion in rat testicular interstitial cells

The aim of this study was to investigate the mechanism by which propylthiouracil (PTU) exerts its inhibitory effects on the production of testosterone by rat testicular interstitial cells. The plasma testosterone concentration was decreased 60 and 120 min after an intravenous infusion of PTU (10 or 20 mg kg(-1)), but the concentration of plasma T(4) was unaffected by the drug treatment. Exposure of anterior pituitary tissue to PTU (3-12 mM) in vitro did not affect either basal or gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) release. PTU (3 - 12 mM) inhibited both the basal and the human chorionic gonadotropin (hCG, 0.05 i.u. ml(-1))-stimulated release of testosterone from rat testicular tissue in vitro; at the highest concentration tested (12 mM), it also inhibited the forskolin or 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cyclic AMP)-stimulated release of testosterone. The 25-OH-cholesterol (10(-7)-10(-5) M)-stimulated release of pregnenolone and testosterone by the testicular interstitial cells was inhibited by PTU (12 mM, P<0.05). The results suggest that the inhibitory actions of PTU on testosterone secretion are exerted, at least in part, at the testicular level through a mechanism which is independent of thyroid status and which involves a reduction in P450scc activity and, hence, in the conversion of cholesterol to pregnenolone.

Effects of evodiamine on the secretion of testosterone in rat testicular interstitial cells

Evodiamine, a bioactive component isolated from the Chinese medicine Wu-chu-yu, exhibits vasodilative and antianoxic action. Although evodiamine indeed has many biological effects, its effects on the endocrine system are not clear. The present study explored the effects of evodiamine on testosterone secretion in vitro. Rat collagenase-dispersed testicular interstitial cells (TICs) were incubated with evodiamine (0 to 10(-4) mol/L) in the presence or absence of human chorionic gonadotropin (hCG), forskolin, 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), or steroidogenic precursors (including 25-hydroxycholesterol, pregnenolone, progesterone, 17alpha-hydroxyprogesterone, and androstenedione) at 34 degrees C for 1 hour. The testosterone concentration in the media samples was measured by radioimmunoassay. Evodiamine 10(-4) mol/L was effective to reduce both basal and hCG-stimulated testosterone secretion in rat TICs after 1, 2, or 4 hours of incubation. The stimulatory effect of forskolin on testosterone release in TICs was prevented by administration of evodiamine. Evodiamine 10(-4) mol/L also decreased 8-Br-cAMP- and androstenedione-stimulated testosterone secretion. These results suggest that evodiamine reduces testosterone secretion in rat TICs via a mechanism involving reduced activity of cAMP-related pathways and 17beta-hydroxysteroid dehydrogenase (17beta-HSD).

Inhibition of salmon calcitonin on secretion of progesterone and GnRH-stimulated pituitary luteinizing hormone

The effects of salmon calcitonin (sCT) on the production of progesterone and secretion of luteinizing hormone (LH) were examined in female rats. Diestrous rats were intravenously injected with saline, sCT, human chorionic gonadotropin (hCG), or hCG plus sCT. Ovariectomized (Ovx) rats were injected with saline or sCT. In the in vitro experiments, granulosa cells and anterior pituitary glands (APs) were incubated with the tested drugs. Plasma LH levels of Ovx rats were reduced by sCT injection. Administration of sCT decreased the basal and hCG-stimulated progesterone release in vivo and in vitro. 8-Bromo-cAMP dose dependently increased progesterone production but did not alter the inhibitory effect of sCT. H-89 did not potentiate the inhibitory effect of sCT. Higher doses of 25-hydroxycholesterol and pregnenolone stimulated progesterone production and diminished the inhibitory effects of sCT. sCT did not decrease basal release of LH by APs, but pretreatment of sCT decreased gonadotropin-releasing hormone (GnRH)-stimulated LH secretion. These results suggested that sCT inhibits progesterone production in rats by preventing the stimulatory effect of GnRH on LH release in rat APs and acting directly on ovarian granulosa cells to decrease the activities of post-cAMP pathway and steroidogenic enzymes.

Inhibitory effect of digoxin on testosterone secretion through mechanisms involving decreases of cyclic AMP production and cytochrome P450scc activity in rat testicular interstitial cells

1. In vivo and in vitro experiments were performed to examine inhibitory effects of digoxin on testosterone secretion and to determine possible underlying mechanisms. 2. A single intravenous injection of digoxin (1 microg kg(-1)) decreased the basal and human chorionic gonadotropin (hCG)-stimulated plasma testosterone concentrations in adult male rats. 3. Digoxin (10(-7) - 10(-4) M) decreased the basal and hCG-stimulated release of testosterone from rat testicular interstitial cells in vitro. 4. Digoxin (10(-7) - 10(-4) M) also diminished the basal and hCG-stimulated production of cyclic 3':5'-adenosine monophosphate (AMP) and attenuated the stimulatory effects of forskolin and 8-Br-cyclic AMP on testosterone production by rat testicular interstitial cells. 5. Digoxin (10(-4) M) inhibited cytochrome P450 side chain cleavage enzyme (cytochrome P450sec) activity (conversion of 25-hydroxy cholesterol to pregnenolone) in the testicular interstitial cells but did not influence the activity of other steroidogenic enzymes. 6. These results suggest that digoxin inhibits the production of testosterone in rat testicular interstitial cells, at least in part, via attenuation of the activities of adenylyl cyclase and cytochrome P450sec.

Effects of methanol extract of Chansu on hypothalamic-pituitary-testis function in rats

Chansu, a galenical preparation of the dried white venom of Chinese Bufo bufo gargarizans, is one of the major components of Kyushin, a traditional Chinese medicine. Kyushin is reported to have a cardiotonic effect that has been suggested to be due to the action of bufadienolides such as bufalin and cinobufagin. Recently, we found that administration of bufalin in male rats diminished the luteinizing hormone (LH) response to gonadotropin-releasing hormone (GnRH) and the secretion of testosterone both in vivo and in vitro. These observations suggest that Chansu may possess hypogonadal effects in male rats. In the present study, the effects of the methanol extract of Chansu on hypothalamic-pituitary-testicular function in male rats were examined. Crude Chansu was extracted by methanol and purified by a Sep-Pak C18 column. No activity of bufalin, cinobufagin, estradiol, or digoxin in purified methanol extract was detected; all Chansu used in this study was the purified methanol extract. A single intravenous injection of Chansu resulted in a decrease of the basal (20% to 55%) and human chorionic gonadotropin (hCG)-induced (35% to 40%) levels of plasma testosterone and the GnRH-induced level of plasma LH (25% to 30%). Administration of Chansu in vitro decreased basal and hCG-stimulated testosterone production by 60% to 70% and 40% to 60%, respectively, as well as spontaneous and forskolin- or 3-isobutyl-1-methylxanthine (IBMX)-induced accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) by 30% to 45% in rat testicular interstitial cells. Although LH release by rat anterior pituitary glands was diminished, GnRH release by the rat mediobasal hypothalamus was enhanced by administration of Chansu in vitro. These results suggest that the bufalin-free extracts of Chansu inhibit testosterone secretion in rats, in part, due to (1) a decreased production of testicular cAMP, (2) a decreased response of testosterone to gonadotropin, and (3) a reduction of the LH response to GnRH.