Nitric oxide production by cultured rat Leydig cells

Role of serotonin, estrogen, and TNF-α in the paroxetine-impaired steroidogenesis and testicular macrophages polarization

BACKGROUND

Paroxetine, a selective serotonin reuptake inhibitor (SSRI) antidepressant, has caused male sexual dysfunction; however, the paroxetine mechanisms of action in testes are still unclear.

OBJECTIVES

Paroxetine serotonergic effects in testes were evaluated, focusing on steroidogenesis and the correlation between macrophages population and possible TNF-α-derived oxidative stress. We also verified whether the changes are reversible following treatment interruption.

MATERIALS AND METHODS

Adult rats received paroxetine (PG35 and PG65) or tap water (CG) for 35 days. PG65 was maintained without treatment for 30 more days. Intratesticular testosterone (IT), nitrite, and malondialdehyde concentrations were measured. To confirm serotonergic and estrogenic effects, Htr1b and Esr1 expressions were analyzed. The daily sperm production (DSP), frequency of abnormal seminiferous tubules (ST), SC number, ST area, and Leydig cells nuclear area (LCnu) were evaluated. TUNEL+ germ cells, M1 (CD68+ ), and M2 (Perls+ ) macrophages were quantified. 17β-HSD7, CYP19A1, NDRG2, oxytocin, TNF-α, and iNOS were evaluated by immunoreactions. Oxytocin and NDRG2 protein levels as well as Tnfa mRNA expression were also analyzed.

RESULTS

The Htr1b downregulation in testes confirmed the paroxetine serotonergic effect. The testicular sections showed abnormal ST frequency, ST atrophy and reduction of DSP, LCnu, SC number and Perls+ macrophages. TUNEL+ germ cells and LC were associated with strong NDRG2 immunoexpression. Paroxetine reduced IT levels and 17β-HSD7 immunoexpression in parallel to increased CYP19A1, oxytocin, TNF-α and iNOS. Esr1 and Tnfa overexpression and increased number of CD68+ macrophages were also observed together with high nitrite and malondialdehyde levels. Most parameters were not recovered in PG65.

CONCLUSIONS

Paroxetine serotonergic effect impairs LC steroidogenesis, via aromatization, increasing estrogen/testosterone ratio, which in turn upregulate NDRG2, promoting apoptosis, and impairing sperm production. Serotonin-estrogen pathways may be responsible for M2/M1 polarization, Tnfa upregulation, and induction of oxidative stress. The unrecovered testicular changes after treatment discontinuation are due to persistent paroxetine serotonin/estrogen effects.

Nitric oxide-induced lipophagic defects contribute to testosterone deficiency in rats with spinal cord injury

Introduction

Males with acute spinal cord injury (SCI) frequently exhibit testosterone deficiency and reproductive dysfunction. While such incidence rates are high in chronic patients, the underlying mechanisms remain elusive.

Methods and results

Herein, we generated a rat SCI model, which recapitulated complications in human males, including low testosterone levels and spermatogenic disorders. Proteomics analyses showed that the differentially expressed proteins were mostly enriched in lipid metabolism and steroid metabolism and biosynthesis. In SCI rats, we observed that testicular nitric oxide (NO) levels were elevated and lipid droplet-autophagosome co-localization in testicular interstitial cells was decreased. We hypothesized that NO impaired lipophagy in Leydig cells (LCs) to disrupt testosterone biosynthesis and spermatogenesis. As postulated, exogenous NO donor (S-nitroso-N-acetylpenicillamine (SNAP)) treatment markedly raised NO levels and disturbed lipophagy via the AMPK/mTOR/ULK1 pathway, and ultimately impaired testosterone production in mouse LCs. However, such alterations were not fully observed when cells were treated with an endogenous NO donor (L-arginine), suggesting that mouse LCs were devoid of an endogenous NO-production system. Alternatively, activated (M1) macrophages were predominant NO sources, as inducible NO synthase inhibition attenuated lipophagic defects and testosterone insufficiency in LCs in a macrophage-LC co-culture system. In scavenging NO (2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO)) we effectively restored lipophagy and testosterone levels both in vitro and in vivo, and importantly, spermatogenesis in vivo. Autophagy activation by LYN-1604 also promoted lipid degradation and testosterone synthesis.

Discussion

In summary, we showed that NO-disrupted-lipophagy caused testosterone deficiency following SCI, and NO clearance or autophagy activation could be effective in preventing reproductive dysfunction in males with SCI.

Nitric oxide synthase and its function in animal reproduction: an update

Nitric oxide (NO), a free radical labile gas, is involved in the regulation of various biological functions and physiological processes during animal reproduction. Recently, increasing evidence suggests that the biological role and chemical fate of NO is dependent on dynamic regulation of its biosynthetic enzyme, three distinct nitric oxide synthase (NOS) according to their structure, location and function. The impact of NOS isoforms on reproductive functions need to be timely elucidated. Here, we focus on and the basic background and latest studies on the development, structure, importance inhibitor, location pattern, complex functions. Moreover, we summarize the exactly mechanisms which involved some cell signal pathways in the regulation of NOS with cellular and molecular level in the animal reproduction. Therefore, this growing research area provides the new insight into the important role of NOS male and female reproduction system. It also provides the treatment evidence on targeting NOS of reproductive regulation and diseases.

Aging has the opposite effect on cAMP and cGMP circadian variations in rat Leydig cells

The Leydig cell physiology displays a circadian rhythm driven by a complex interaction of the reproductive axis hormones and circadian system. The final output of this regulatory process is circadian pattern of steroidogenic genes expression and testosterone production. Aging gradually decreases robustness of rhythmic testosterone secretion without change in pattern of LH secretion. Here, we analyzed effect of aging on circadian variation of cAMP and cGMP signaling in Leydig cells. Results showed opposite effect of aging on cAMP and cGMP daily variation. Reduced amplitude of cAMP circadian oscillation was probably associated with changed expression of genes involved in cAMP production (increased circadian pattern of Adcy7, Adcy9, Adcy10 and decreased Adcy3); cAMP degradation (increased Pde4a, decreased Pde8b, canceled rhythm of Pde4d, completely reversed circadian pattern of Pde7b and Pde8a); and circadian expression of protein kinase A subunits (Prkac/PRKAC and Prkar2a). Aging stimulates expression of genes responsible for cGMP production (Nos2, Gucy1a3 and Gucy1b3/GUCYB3) and degradation (Pde5a, Pde6a and Pde6h) but the overall net effect is elevation of cGMP circadian oscillations in Leydig cells. In addition, the expression of cGMP-dependent kinase, Prkg1/PRKG1 is up-regulated. It seems that aging potentiate cGMP- and reduce cAMP-signaling in Leydig cells. Since both signaling pathways affect testosterone production and clockwork in the cells, further insights into these signaling pathways will help to unravel disorders linked to the circadian timing system, aging and reproduction.

Protective Effect of Adrenomedullin on Rat Leydig Cells from Lipopolysaccharide-Induced Inflammation and Apoptosis via the PI3K/Akt Signaling Pathway ADM on Rat Leydig Cells from Inflammation and Apoptosis

This study was carried out to investigate whether ADM can modulate LPS-induced inflammation and apoptosis in rat Leydig cells. Leydig cells were treated with ADM before LPS-induced cytotoxicity. We determined the concentrations of ROS, MDA, GSH, LDH, and testosterone and the MMP. The mRNA levels of IL-1, IL-6, iNOS, and COX-2 were obtained, and the concentrations of IL-1, IL-6, NO, and PGE2 were determined. Apoptosis was assessed by TUNEL and detection of DNA fragmentation. The levels of mRNA and protein were determined for Bcl-2, Bax, caspase-3, and PARP. The protein contents for total and p-Akt were measured. ADM pretreatment significantly elevated the MMP and testosterone concentration and reduced the levels of ROS, MDA, GSH, and LDH. ADM pretreatment significantly decreased the mRNA levels of IL-1, IL-6, iNOS, and COX-2 and the concentrations of IL-1, IL-6, NO, and PGE2. LPS-induced TUNEL-positive Leydig cells were significantly decreased by ADM pretreatment, a result further confirmed by decreased DNA fragmentation. ADM pretreatment decreased apoptosis by significantly promoting Bcl-2 and inhibiting Bax, caspase-3, and PARP expressions. The LPS activity that reduced p-Akt level was significantly inhibited by ADM pretreatment. ADM protected rat Leydig cells from LPS-induced inflammation and apoptosis, which might be associated with PI3K/Akt mitochondrial signaling pathway.

Effects of different cryoprotectants on the cryopreservation of cattle testicular tissue

Abstract. Cryopreservation of testicular tissue is a new option in fertility preservation for prepubertal male animals. The purpose of this study was to explore the effects of different cryoprotectant agents (CPAs) at various concentrations on testes after the cryopreservation of calf testicular tissue. These experiments selected dimethyl sulfoxide (DMSO), glycerol, propylene glycol (PrOH), and sucrose as CPAs in varying doses (2.5, 5, 7.5, 10, 12.5, 15, 17.5, and 20 %; v/v) in 8-month-old calf testicular tissue that was frozen and preserved. Then, cell viability, testosterone production, malondialdehyde (MDA) level, and superoxide dismutase (SOD) level were detected and analyzed following cryopreservation. The results showed that the optimal concentrations of DMSO, PrOH, glycerol, and sucrose were 10, 10, 7.5, and 10 %, respectively. Compared to the optimal concentrations of CPAs, cell viability and testosterone production decreased significantly at a lower and higher CPA concentration (P < 0.05). At the optimal concentrations of CPAs, the DMSO group showed higher cell viability and testosterone production than other CPA groups (P < 0.05). Compared to the optimal concentration of CPAs, the MDA level increased and the SOD level decreased at a lower or higher concentration of CPAs, but there was no significant difference (P > 0.05). Cell viability was significantly positively correlated with testosterone production (P < 0.05). In conclusion, DMSO provided the most effective protection for calf testicular tissue cryopreservation and the optimal concentration was 10 %.

Adrenomedullin attenuates interleukin-1β-induced inflammation and apoptosis in rat Leydig cells via inhibition of NF-κB signaling pathway

The aim of this paper is to investigate the protective effects of adrenomedullin (ADM) on interleukin-1β (IL-1β)-induced inflammation and apoptosis in rat Leydig cells and its underlying molecular mechanisms. Leydig cells were isolated from adult Sprague-Dawley rats. The cell culture was established by adding ADM 2h prior to 24h treatment with IL-1β-induced cytotoxicity. We detected cell viability and concentrations of testosterone, reactive oxygen species (ROS), malondialdehyde (MDA), and reduced glutathione (GSH). Gene expression levels were measured for inducible nitric oxide synthase (iNOS) and cyclo-oxygenase-2 (COX-2). Concentrations were detected for nitric oxide (NO) and prostaglandin E2 (PGE2). Apoptosis was assessed using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL). Levels of gene expression and protein were detected for Bcl-2, Bax, caspase-3, and poly adenosine diphosphate-ribose polymerase (PARP). Protein levels were measured for nuclear factor kappa B (NF-κB) p65 and IκBα. ADM reduced IL-1β-induced cytotoxicity. ADM pretreatment significantly increased testosterone concentrations and decreased ROS, MDA, and GSH concentrations. ADM pretreatment inhibited IL-1β-induced inflammation in Leydig cells by decreasing the gene expression levels of iNOS and COX-2, as well as the concentrations of NO and PGE2. ADM pretreatment further decreased the number of TUNEL-positive stained Leydig cells, as confirmed by the increase in gene expression and protein levels of Bcl-2 and the decrease of Bax, caspase-3, and PARP levels. Moreover, ADM pretreatment inhibited NF-κB p65 phosphorylation and IκBα phosphorylation and degradation. ADM has potential anti-inflammatory and anti-apoptotic properties in IL-1β-induced rat Leydig cells, which might be related to NF-κB signaling pathway.

N (G)-nitro-L-arginine Methyl Ester Protects Against Hormonal Imbalances Associated with Nicotine Administration in Male Rats

Background:

The administration of nicotine is associated with altered hormonal imbalances and increased serum and testicular nitric oxide (NO) level.

Aim:

This study sought to investigate the effects of NO inhibition with N^G-nitro-L-arginine methyl ester (L-NAME) on altered hormonal imbalance in adult male albinorats.

Materials and Methods:

Rats were administered with 0.5 mg/kg body weight (BW) and 1.0 mg/kg BW nicotine and were treated with L-NAME in the drinking water or drinking water alone for 30 days. Serum was analyzed for testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin using radioimmunoassay.

Results:

Nicotine administration significantly decreased (P < 0.05) testosterone in the low and high dose treated groups and FSH in the high dose treated group when compared with the control group. There was a significant increase (P < 0.05) in mean LH and prolactin level in the high dose treated group when compared with the control. Concomitant treatment with nicotine and L-NAME produced significant increases in testosterone and FSH, and a decrease in prolactin in 1.0 mg/kg BW. L-NAME alone did not lead to a significant increase in testosterone when compared with control.

Conclusion:

These data demonstrate that the suppressive effects of nicotine on testosterone level of the adult male rat can be prevented by NOS blockade with L-NAME. It appears that these beneficial effects are mediated primarily within the gonad; however, the involvement of the pituitary cannot be totally ruled out.

Increase in the expression of inducible nitric oxide synthase on exposure to bisphenol A: a possible cause for decline in steroidogenesis in male mice

Bisphenol A (BPA) is a well-known plasticizer and xenoestrogen that is responsible for many acquired reproductive difficulties, especially in men. Despite the prevalence of BPA in society, the mechanism behind reproductive deficits remains elusive. The present study investigates the mode of BPA's action by evaluating its effect on the expression of inducible nitric oxide synthase (iNOS) and steriodogenic acute regulatoryprotein (StAR) in male mice testis. Swiss albino mice were treated with a range BPA concentrations of 0.5, 50 and 100μg/kg body weight/day intraperitoneally for 60 days. Several markers of oxidative stress and male fertility were investigated. Nitrite levels, malondialdehyde levels and testicular injury scores were elevated whereas the sperm count, serum testosterone levels and catalase activity were reduced in the BPA groups. Mechanistically, an increase in iNOS expression was observed in the testis whereas the expression of the StAR was down regulated in the BPA treated mouse. These results suggest that BPA induces oxidative stress by altering the expression of iNOS, which consequently leads to the down regulation of StAR expression in the testis of male mouse.

Overexpression of Endothelial Nitric Oxide Synthase in Transgenic Mice Accelerates Testicular Germ Cell Apoptosis Induced by Experimental Cryptorchidism

Surgical induction of cryptorchidism in experimental animals causes testicular germ cell apoptosis and infertility. The mechanisms of germ cell apoptosis have been associated with oxidative stress or testicular exposure to elevated temperature. Nitric oxide (NO) has been associated with apoptosis in a number of cell types. The objective of this study was to investigate whether overexpression of endothelial NO synthase (eNOS) could accelerate apoptosis of germ cells in the testes of transgenic mice. There are 3 NOS isoforms, and we restricted the analysis to eNOS at this time. For the colocalization of eNOS, staining in degenerating germ cells that were apoptotic cells suggested that eNOS may be related to germ cell apoptosis. eNOS overexpression in the testes of eNOS transgenic (eNOS-Tg) mice was examined using Western blot analysis. Unilateral cryptorchidism was surgically induced in both eNOS-Tg and wild-type (WT) adult mice. The testes were evaluated 1, 3, 5, 7, and 14 days after the operation by weighing the testes and examining histopathologic features and cell apoptosis using in situ microscopic analysis of DNA fragmentation. Immunoblotting for eNOS protein demonstrated increases in eNOS protein expression in testes, as well as the lung and aorta. In eNOS-Tg mice, weight reduction of cryptorchid testis was significantly increased on days 3, 5, and 7 (P = .02, .02, and .04, respectively). The numbers of spermatocytes and spermatids of eNOS-Tg cryptorchid testis significantly decreased compared with those of WT cryptorchid testis from day 3 (spermatocytes: P = .04; spermatids: P = .02). Moreover, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling demonstrated that eNOS-Tg mice significantly accelerate germ cell apoptotic changes induced by experimental cryptorchidism compared with WT mice from day 3 (P = .03). We have provided evidence that eNOS plays a functional role in mouse spermatogenesis in cryptorchidism-induced apoptosis.

The expression of inducible nitric oxide synthase (iNOS) in the testis and epididymis of rats with a dihydrotestosterone (DHT) deficiency

In our previous studies, we showed that a finasteride-induced DHT deficiency may cause changes in the morphology of the seminiferous epithelium without any morphological alteration of the epididymis. In this study, we demonstrated the constitutive immunoexpression of inducible nitric oxide synthase (iNOS) in the testis and epididymis of Wistar rats treated with finasteride for 28 days (the duration of two cycles of the seminiferous epithelium) and 56 days (the duration of one spermatogenesis). We noted that a 56-day finasteride treatment mainly caused a decrease in the level of circulating DHT, as well as a statistically insignificant decrease in the level of T. The hormone deficiency also led to a change in the iNOS immnoexpression in the testis and epididymis of the finasteride-treated rats. In vitro, DHT did not modify NO production by the epithelial cells of the caput epididymis even when stimulated with LPS and IFNγ, but it did give rise to an increase in NO production by the epithelial cells of the cauda epididymis without the stimulation. DHT did not have a statistically significant influence on estradiol production by cultured, LPS- and IFNγ-stimulated epithelial cells from the caput and cauda epididymis. In conclusion, our data clearly indicates that a finasterideinduced DHT deficiency intensifies the constitutive expression of iNOS in most rat testicular and epididymal cells, so it can be expected that the expression of inducible nitric oxide synthase (iNOS) could be regulated by DHT. On the other hand, the profile of the circulating DHT and T levels strongly suggests that the regulation of constitutive iNOS expression is complex and needs more detailed study.

Involvement of nitric oxide synthase in the mechanism of histamine-induced inhibition of Leydig cell steroidogenesis via histamine receptor subtypes in Sprague-Dawley rats

This study was conducted to shed light on the so far unexplored intracellular mechanisms underlying negative modulation of Leydig cell steroidogenesis by histamine (HA). Using the MA-10 cell line and highly purified rat Leydig cells as experimental models, we examined the effect of the amine on biochemical steps known to be modulated by HA or involved in LH/hCG action. In agreement with previous findings, HA at 10 microM showed a potent inhibitory effect on hCG-stimulated steroid synthesis, regardless of the gonadotropin concentration used. Moreover, HA decreased not only LH/hCG-induced cAMP production but also steroid synthesis stimulated by the permeable cAMP analog dibutyryl cAMP (db-cAMP). Considering the post-cAMP sites of HA action, it is shown herein that HA markedly inhibited db-cAMP-stimulated steroidogenic acute regulatory (STAR) protein expression, as well as steps catalyzed by P450-dependent enzymes, mainly the conversion of cholesterol to pregnenolone by cholesterol side-chain cleavage enzyme (CYP11A). The antisteroidogenic action of HA was blocked by addition of the phospholipase C (PLC) inhibitor U73122, and HA significantly augmented inositol triphosphate (IP3) production, suggesting a major role for the PLC/IP3 pathway in HA-induced inhibition of Leydig cell function. Finally, HA increased nitric oxide synthase (NOS) activity, and the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) markedly attenuated the effect of the amine on steroid synthesis. On the basis of our findings, HA antagonizes the gonadotropin action in Leydig cells at steps before and after cAMP formation. NOS activation is the main intracellular mechanism by which HA exerts its antisteroidogenic effects.

Opposing effects of D-aspartic acid and nitric oxide on tuning of testosterone production in mallard testis during the reproductive cycle

D-Aspartic acid (D-Asp) and nitric oxide (NO) play an important role in tuning testosterone production in the gonads of male vertebrates. In particular, D-Asp promotes either the synthesis or the release of testosterone, whereas NO inhibits it. In this study, we have investigated for the first time in birds the putative effects of D-Asp and NO on testicular testosterone production in relation to two phases of the reproductive cycle of the adult captive wild-strain mallard (Anas platyrhynchos) drake. It is a typical seasonal breeder and its cycle consists of a short reproductive period (RP) in the spring (April-May) and a non reproductive period (NRP) in the summer (July), a time when the gonads are quiescent. The presence and the localization of D-Asp and NO in the testis and the trends of D-Asp, NO and testosterone levels were assessed during the main phases of the bird's reproductive cycle. Furthermore, in vitro experiments revealed the direct effect of exogenously administered D-Asp and NO on testosterone steroidogenesis.

METHODS

By using immunohistochemical (IHC) techniques, we studied the presence and the distributional pattern of D-Asp and NO in the testes of RP and NRP drakes. D-Asp levels were evaluated by an enzymatic method, whereas NO content, via nitrite, was assessed using biochemical measurements. Finally, immunoenzymatic techniques determined testicular testosterone levels.

RESULTS

IHC analyses revealed the presence of D-Asp and NO in Leydig cells. The distributional pattern of both molecules was in some way correlated to the steroidogenic pathway, which is involved in autocrine testosterone production. Indeed, whereas NO was present only during the NRP, D-Asp was almost exclusively present during the RP. Consistently, the high testosterone testicular content occurring during RP was coupled to a high D-Asp level and a low NO content in the gonad. By contrast, in sexually inactive drakes (NRP), the low testosterone content in the gonad was coupled to a low D-Asp content and to a relatively high NO level. Consequently, to determine the exogenous effects of the two amino acids on testosterone synthesis, we carried out in vitro experiments using testis sections deriving from both the RP and NRP. When testis slices were incubated for 60 or 120 min with D-Asp, testosterone was enhanced, whereas in the presence of L-Arg, a precursor of NO, it was inhibited.

CONCLUSION

Our results provide new insights into the involvement of D-Asp and NO in testicular testosterone production in the adult captive wild-strain mallard drake. The localization of these two molecules in the Leydig cells in different periods of the reproductive cycle demonstrates that they play a potential role in regulating local testosterone production.

Testosterone production in mice lacking inducible nitric oxide synthase expression is sensitive to restraint stress

Immobilization stress (IMO) induces a rapid increase in glucocorticoid secretion [in rodents, corticosterone CORT)] and this is associated with decreased circulating testosterone (T) levels. Nitric oxide (NO), a reactive free radical and neurotransmitter, has been reported to be produced at higher rates in tissues such as brain during stress. The biosynthesis of T is also known to be dramatically suppressed by NO. Specifically, the inducible isoform of nitric oxide synthase (iNOS) was directly implicated in this suppression. To assess the respective roles of CORT and NO in stress-mediated inhibition of T production, adult wild-type (WT) and inducible nitric oxide synthase knockout (iNOS(-/-)) male mice were evaluated. Animals of each genotype were assigned to either basal control or 3-h IMO groups. Basal plasma and testicular T levels were equivalent in both genotypes, whereas testicular weights of mutant mice were significantly higher compared with WT animals. Exposure to 3-h IMO increased plasma CORT and decreased T concentrations in mice of both genotypes. Testicular T levels were also affected by stress in WT and mutant males, being sharply reduced in both genotypes. However, the concentrations of nitrite and nitrate, the stable metabolites of NO measured in testicular extracts, did not differ between control and stressed WT and iNOS(-/-) mice. These results support the hypothesis that CORT, but not NO, is a plausible candidate to mediate rapid stress-induced suppression of Leydig cell steroidogenesis.

Interleukin-1beta signals through a c-Jun N-terminal kinase-dependent inducible nitric oxide synthase and nitric oxide production pathway in Sertoli epithelial cells

Our recent Sertoli cell (SC) studies showed that the c-Jun N-terminal kinase (JNK) and inducible cyclooxygenase-2 (COX-2) pathways are key regulatory components of IL (IL-1alpha, IL-1beta, and IL-6) expression and START-domain containing StARD1 and StARD5 proteins. IL-1beta regulates SC autocrine/paracrine activities and subsequently influences developing germ cells and spermatogenesis. This study was designed to evaluate whether IL-1beta mediates high-output inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in these specialized epithelial cells and characterize gonadotropin and cytokine-regulation of NO. Purified SCs were maintained in serum-free cultures and treated with FSH (100 ng-1 microg/ml) or IL-1beta (10 ng/ml) in time-course studies. To determine obligatory intracellular pathways, treatments were conducted with or without activity inhibitors: COX-2 selective (NS-398, 10 microM) or JNK (SP600125, 10 microM) for 1, 3, 6, and 24 h. NOS mRNAs and proteins were evaluated by RT-PCR and Western analysis, respectively. NO and reactive oxygen species were measured by flow cytometry and ELISA. IL-1beta transiently induces intracellular NO (30 min) but not reactive oxygen species. Subsequently, iNOS mRNA and protein expression (3-6 h) significantly increased after IL-1beta but not FSH stimulation, and in time-dependent manner, markedly increased extracellular NO (24 h, 8-fold). No change in the constitutive endothelial NOS isoform was observed. Inhibition of JNK, but not COX-2, activity inhibits IL-1beta-induced iNOS expression and NO production. Such findings suggest that intra- and extracellular NO within the tubule may alert SCs monitoring the microenvironment to an aberrant cytokine, triggering antioxidant and antiinflammatory activities to avoid disruption of spermatogenesis.

Activation of a neural brain-testicular pathway rapidly lowers Leydig cell levels of the steroidogenic acute regulatory protein and the peripheral-type benzodiazepine receptor while increasing levels of neuronal nitric oxide synthase

Activation of a neural brain-testicular pathway by the intracerebroventricular injection of the beta-adrenergic agonist isoproterenol (ISO), the hypothalamic peptide corticotropin-releasing factor (CRF), or alcohol (EtOH) rapidly decreases the testosterone (T) response to human chorionic gonadotropin. To elucidate the intratesticular mechanisms responsible for this phenomenon, we investigated the influence of intracerebroventricular-injected ISO, CRF, or EtOH on levels of the steroidogenic acute regulatory (StAR) protein, the peripheral-type benzodiazepine receptor (PBR), and the cytochrome P450 side-chain cleavage enzyme in semipurified Leydig cells. ISO (10 microg), CRF (5 microg), or EtOH (5 microl of 200 proof, a dose that does not induce neuronal damage nor leaks to the periphery) rapidly decreased StAR and PBR but not cytochrome P450 side-chain cleavage enzyme protein levels. Levels of the variant of the neuronal nitric oxide synthase (nNOS) that is restricted to Leydig cells, TnNOS, significantly increased in response to ISO, CRF, and EtOH over the time course of altered StAR/PBR concentrations. However, pretreatment of the rats with N(w)nitro-arginine methylester, which blocked ISO-induced increases in TnNOS, neither restored the T response to human chorionic gonadotropin nor prevented the decreases in StAR and PBR. These results provide evidence of concomitant changes in Leydig cell StAR and PBR levels in live rats. They also indicate that activation of a neural brain-testicular pathway rapidly decreases concentrations of these steroidogenic proteins while up-regulating testicular NO production. However, additional studies are necessary to elucidate the functional role played by this gas in our model.

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.

Calcium-sensing receptor activation induces nitric oxide production in H-500 Leydig cancer cells

Nitric oxide (NO) is a versatile second messenger. NO is produced by Leydig cells, where NO is a negative regulator of steroidogenesis. In cancer cells, NO is thought to have mutagenic and proliferative effects. We have previously shown that the calcium-sensing receptor (CaR) has promalignant effects in rat H-500 Leydig cancer cells, a model for humoral hypercalcemia of malignancy. Calcium, the major physiological ligand of the CaR, is a recognized intracellular cofactor in the process of NO production by virtue of its positive modulation of neuronal and endothelial nitric oxide synthase (NOS), but importantly, not of inducible (i) NOS activity. iNOS activity is regulated by changes in its expression level. Therefore, we investigated whether CaR activation changes iNOS expression. We found that high extracellular calcium (Cao2+) upregulates the level of mRNA for iNOS, whereas no change was seen in neuronal or endothelial NOS, as assessed by microarray and real-time PCR, respectively. The high Cao2+-induced iNOS upregulation was also detected by Northern and Western blotting. By quantitative real-time PCR, we showed that calcium maximally upregulates iNOS at 18 h. The effect of calcium was abolished by overexpression of a dominant-negative CaR (R185Q), confirming that the effect of Cao2+ was mediated by the CaR. Cells treated with high calcium had higher NO production than those treated with low calcium, as detected with the NO-specific DAF2-AM dye. This was confirmed in single-cell fluorescence determinations using confocal microscopy. In conclusion, high calcium upregulates the levels of iNOS mRNA and protein as well as NO production in H-500 cells, and the effect of Cao2+ on iNOS expression is mediated by the CaR.

Effects of nitric oxide on aldosterone synthesis and nitric oxide synthase activity in glomerulosa cells from bovine adrenal gland

This study investigated the effects of two NO-releasing agents, diethylenetriamine-NO (deta-NO) and sodium nitroprusside (SNP), on basal, ACTH-, and angiotensin II (AngII)-stimulated aldosterone production in glomerulosa cells from bovine adrenal gland. NO donors inhibited basal and ACTH- or AngII-stimulated aldosterone synthesis in a concentration-dependent manner. Deta-NO and SNP also provoked a concentration-dependent stimulation of cGMP production. However, cGMP was not responsible for the inhibition of aldosterone secretion, because a cGMP analog did not reproduce the inhibitory effect. Moreover, soluble guanylyl cyclase or protein kinase G inhibitors did not revert the inhibitory effect of NO on aldosterone production. NO donors did not modify ACTH-stimulated cAMP production or AngII-stimulated PLC activity stimulation, but inhibited 22[R] hydroxycholesterol- or pregnenolone-stimulated aldosteronogenesis. NO can be synthesized in bovine glomerulosa cells because nitrite production was determined and characterization of NOS activity was also performed. Nitrite accumulation was not modified in the presence of ACTH, AngII, or other factors used to induce iNOS. NOS activity that showed a Michaelis-Menten kinetic was NADPH- and calcium-dependent and was inhibited by two competitive inhibitors, L-NAME and L-NMMA. These results show that NO inhibits aldosterone production in glomerulosa cells acting on P450scc and other P450-dependent steroidogenic enzymes, and these cells display NOS activity suggesting that NO can be produced by constitutive NOS isozymes.

Nitric Oxide/Nitric Oxide Synthase, Spermatogenesis, and Tight Junction Dynamics1

During spermatogenesis, preleptotene and leptotene spermatocytes, residing in the basal compartment of the seminiferous epithelium, must traverse the blood-testis barrier (BTB) to gain entry to the adluminal compartment for further development at late stage VIII and early stage IX of the epithelial cycle. As such, the timely opening and closing of the BTB is crucial to spermatogenesis. A compromise in this process can lead to infertility. Moreover, the BTB is unique in its relative localization in the seminiferous epithelium compared to the tight junctions (TJs) found in other epithelia. Sertoli cell TJs are situated near the basal lamina in the testis, closest to the basement membrane (a modified form of extracellular matrix [ECM]), unlike TJs found in other epithelia, which are found nearest the apical portion of an epithelium, farthest away from ECM. Needless to say, BTB function in the testis is maintained by intricate regulatory mechanisms. In addition to hormones and cytokines, nitric oxide (NO) was recently shown to be a putative TJ regulator in the testis. Perhaps equally important, TJ dynamics in the testis were shown to be regulated, at least in part, by occludin, a TJ-integral membrane protein, via the NO/soluble guanylate cyclase/cGMP/protein kinase G signaling pathway. This minireview summarizes recent advances in the field regarding the role of NO in testicular function, with special emphasis regarding its role in TJ dynamics and the likely implications of these studies for male contraceptive development.

Regulation of Sertoli cell tight junction dynamics in the rat testis via the nitric oxide synthase/soluble guanylate cyclase/3',5'-cyclic guanosine monophosphate/protein kinase G signaling pathway: an in vitro study

Nitric oxide (NO) synthase (NOS) catalyzes the oxidation of L-arginine to NO. NO plays a crucial role in regulating various physiological functions, possibly including junction dynamics via its effects on cAMP and cGMP, which are known modulators of tight junction (TJ) dynamics. Although inducible NOS (iNOS) and endothelial NOS (eNOS) are found in the testis and have been implicated in the regulation of spermatogenesis, their role(s) in TJ dynamics, if any, is not known. When Sertoli cells were cultured at 0.5-1.2 x 10(6) cells/cm(2) on Matrigel-coated dishes or bicameral units, functional TJ barrier was formed when the barrier function was assessed by quantifying transepithelial electrical resistance across the cell epithelium. The assembly of the TJ barrier was shown to associate with a significant plummeting in the levels of iNOS and eNOS, seemingly suggesting that their presence by producing NO might perturb TJ assembly. To further confirm the role of NOS on the TJ barrier function in vitro, zinc (II) protoporphyrin-IX (ZnPP), an NOS inhibitor and a soluble guanylate cyclase inhibitor, was added to the Sertoli cell cultures during TJ assembly. Indeed, ZnPP was found to facilitate the assembly and maintenance of the Sertoli cell TJ barrier, possibly by inducing the production of TJ-associated proteins, such as occludin. Subsequent studies by immunoprecipitation and immunoblotting have shown that iNOS and eNOS are structurally linked to TJ-integral membrane proteins, such as occludin, and cytoskeletal proteins, such as actin, vimentin, and alpha-tubulin. When the cAMP and cGMP levels in these ZnPP-treated samples were quantified, a ZnPP-induced reduction of intracellular cGMP, but not cAMP, was indeed detected. Furthermore, 8-bromo-cGMP, a cell membrane-permeable analog of cGMP, could also perturb the TJ barrier dose dependently similar to the effects of 8-bromo-cAMP. KT-5823, a specific inhibitor of protein kinase G, was shown to facilitate the Sertoli cell TJ barrier assembly. Cytokines, such as TGF-beta and TNF-alpha, known to perturb the Sertoli cell TJ barrier, were also shown to stimulate Sertoli cell iNOS and eNOS expression dose dependently in vitro. Collectively, these results illustrate NOS is an important physiological regulator of TJ dynamics in the testis, exerting its effects via the NO/soluble guanylate cyclase/cGMP/protein kinase G signaling pathway.

Cyclooxygenase 2 pathway mediates IL-1beta regulation of IL-1alpha, -1beta, and IL-6 mRNA levels in Leydig cell progenitors

Prostanoids are arachidonic acid (AA) metabolites derived from the cyclooxygenase (COX1 and COX2 isozymes) pathway and are involved in signal transduction pathways activated by distinct ILs. Although COX1 is the constitutive isoform of COX, IL-1beta is a potent inducer of COX2 expression in distinct cell types. This study was designed to determine whether cyclooxygenases could mediate endogenous cytokine regulation in rat progenitor Leydig cells. COX and IL (IL-1alpha, IL-1beta, and IL-6) mRNAs were measured by PCR and real-time PCR analyses, respectively. COX function was assessed using COX activity inhibitors: indomethacin (INDO; COX1 and COX2 inhibitor) and NS-398 (COX2 selective inhibitor). Our data indicate that endogenous progenitor COX1 mRNA levels are low and are not regulated by IL-1beta. In contrast, COX2 mRNA is induced by IL-1beta at 6, 9, and 24 h. IL-1beta induction of IL mRNAs was in part significantly impaired in the presence of INDO or NS-398. Among the prostanoids tested, prostaglandin E(2) (PGE(2)), PGF(2alpha), and carbaprostacyclin reversed the INDO inhibition of IL production. PGs alone have no (IL-1alpha and IL-1beta) or a modest (IL-6) effect on IL mRNA levels. PGE(2), PGF(2alpha), and PGI(2) measurements show that IL-1beta treatment significantly increases progenitor Leydig cell production of these PGs. Taken together, our data demonstrate that this COX2 cascade is a regulator of cytokines in Leydig progenitors.

Nitric oxide synthase patterns in normal and varicocele testis in adolescents

OBJECTIVE

To determine if the testes of normal adolescents can produce nitric oxide (NO), by assessing NO synthase (NOS) activity, and whether this activity changes in adolescents with left idiopathic varicocele.

PATIENTS AND METHODS

After obtaining informed consent, testicular biopsies were obtained from eight adolescents (mean age 16.4 years; controls) who underwent surgery for inguinal hernia or hydrocele, and from 20 adolescents (mean age 16.2 years) operated for left idiopathic varicocele. Inducible and endothelial NOS (iNOS and eNOS) isoforms were investigated in the biopsy specimens by immunohistochemical localization and Western blot analysis using specific fluorescein-conjugated antibodies.

RESULTS

Both normal and pathological samples expressed eNOS at the level of vessels and Leydig cells. The iNOS was expressed in Leydig cells of normal testes and over-expressed in Leydig cells of varicocele testes.

CONCLUSION

Leydig cells of adolescent testes constitutively express iNOS. Under pathological conditions, e.g. varicocele, iNOS is up-regulated and is a possible source of NO overproduction. These results could be useful in explaining the pathogenesis of both testis and sperm dysfunction in varicocele.

Inducible nitric oxide synthase in the rat testis: evidence for potential roles in both normal function and inflammation-mediated infertility

In vitro data have indicated that nitric oxide (NO) inhibits Leydig cell testosterone production, suggesting that NO may play a role in the suppression of steroidogenesis and spermatogenic function during inflammation. Consequently, we investigated expression of the inflammation-inducible isoform of NO synthase (iNOS) in the inflamed adult rat testis and the ability of a broad-spectrum inhibitor of NO production, L-nitro-L-arginine methyl ester, to prevent Leydig cell dysfunction during inflammation. Unexpectedly, immunohistochemical and mRNA data established that iNOS is expressed constitutively in Leydig cells and in a stage-specific manner in Sertoli, peritubular, and spermatogenic cells in the normal testis. Expression was increased in a dose-dependent manner in all these cell types during lipopolysaccharide (LPS)-induced inflammation. In noninflamed testes, treatment with the NO synthase inhibitor reduced testicular interstitial fluid formation and testosterone production without any effect on serum LH levels. Administration of the inhibitor did not prevent the suppression of testicular interstitial fluid and testosterone production that occurs within 6 h after LPS treatment. Collectively, these data indicate a novel role for iNOS in autocrine or paracrine regulation of the testicular vasculature, Leydig cell steroidogenesis, and spermatogenesis in the normal testis. The data suggest that increased NO is not the major cause of acute Leydig cell dysfunction in the LPS-treated inflammation model, although a role for NO in this process cannot be excluded, particularly at other time points. Moreover, up-regulation of iNOS may contribute to the seminiferous epithelium damage caused by LPS-induced inflammation.

Induction of nitric oxide synthase activity in adrenal cells

The induction of nitric oxide synthase (NOS) II by bacterial lypopolysaccharide (LPS) was studied in a steroidogenic mouse tumor adrenal cell line (Y1). Conditioned media from LPS-stimulated peritoneal macrophages induced an increase in NOS II expression as shown by western and northern blot analysis. Accordingly, in the presence of conditioned media an increase in nitrite levels was observed. In addition, steroid production was significantly decreased. In conclusion, NOS II expression could be induced in steroidogenic cells with a concomitant inhibition of steroid production.

Biphasic effect of nitric oxide on testosterone and cyclic GMP production by purified rat Leydig cells cultured in vitro

Nitric oxide (NO) biphasically modulates osteoclast function and sperm motility by exerting a positive effect at low concentrations and a negative effect at high concentrations. We therefore tested whether NO exerts a comparable effect on testosterone secretion by cultured rat Leydig cells. Three NO-donors, S-nitroso-N-acetylpenicillamine (SNAP), diethylamine/nitric oxide complex sodium salt (DEA/NO) and diethylenetriamine nitric oxide adduct (DETA/NO) were administered in a wide range of concentrations (10(-8)-10(-3) M for 3 h) to Percoll-purified Leydig cells from adult rats. These drugs raised testosterone and cGMP secretion when used at low concentrations (10(-8)-10(-5) M); however, they inhibited testosterone, but did not affect cGMP, secretion at concentrations higher than 10(-5) M. Administration of the NO scavenger haemoglobin (160 micrograms/mL) prevented both the stimulatory and the inhibitory effect of these drugs. Nitrite accumulation was measured as a marker of NO released by the drugs in our in vitro system; it fell within the range of control media in the presence of NO-donor concentrations lower than 10(-5) M, but was several-fold higher in the media of cells treated with concentrations of the NO-donors greater than 10(-5) M. These data show that (1) NO exerts a biphasic effect on testosterone secretion, which is stimulatory at low and inhibitory at high concentrations; (2) the stimulatory effect of NO is mediated by cGMP, the classic second messenger for NO action.