Nitric oxide: an autocrine regulator of human granulosa-luteal cell steroidogenesis

Cumulus Cell Transcriptome after Cumulus-Oocyte Complex Exposure to Nanomolar Cadmium in an In Vitro Animal Model of Prepubertal and Adult Age

Cadmium (Cd), a highly toxic pollutant, impairs oocyte fertilization, through oxidative damage on cumulus cells (CCs). This study analysed the transcriptomic profile of CCs of cumulus-oocyte complexes (COCs) from adult and prepubertal sheep, exposed to Cd nanomolar concentration during in vitro maturation. In both age-groups, CCs of matured oocytes underwent RNA-seq, data analysis and validation. Differentially expressed genes (DEGs) were identified in adult (n = 99 DEGs) and prepubertal (n = 18 DEGs) CCs upon Cd exposure. Transcriptomes of adult CCs clustered separately between Cd-exposed and control samples, whereas prepubertal ones did not as observed by Principal Component Analysis. The transcriptomic signature of Cd-induced CC toxicity was identified by gene annotation and literature search. Genes associated with previous studies on ovarian functions and/or Cd effects were confirmed and new genes were identified, thus implementing the knowledge on their involvement in such processes. Enrichment and validation analysis showed that, in adult CCs, Cd acted as endocrine disruptor on DEGs involved in hormone biosynthesis, cumulus expansion, regulation of cell signalling, growth and differentiation and oocyte maturation, whereas in prepubertal CCs, Cd affected DEGs involved in CC development and viability and CC-oocyte communications. In conclusion, these DEGs could be used as valuable non-invasive biomarkers for oocyte competence.

Chronic nitrate administration increases the expression the genes involved in the browning of white adipose tissue in female rats

Nitrate, a nitric oxide (NO) donor, has antiobesity effect in female rats. This study hypothesized that the antiobesity effect of nitrate in female rats is due to the browning of white adipose tissue (WAT). Female Wistar rats (aged 8 months) were divided into two groups (n = 10/group): the control group received tap water and the nitrate group received water containing 100 mg/L of sodium nitrate for 9 months. At months 0, 3, 6, and 9, obesity indices were measured. At month 9, gonadal adipose tissue was used to measure messenger RNA (mRNA) and protein levels of peroxisome proliferator-activated receptor-γ (PPAR-γ), PPAR-γ coactivator 1-α (PGC1-α), uncoupling protein 1 (UCP1), and adipocyte density and area. After the 9-month intervention, nitrate-treated rats had lower body weight, body mass index, thoracic circumference, and abdominal circumference by 6.4% (p = .012), 9.1% (p = .029), 6.0% (p = .056), and 5.7% (p = .098), respectively. In addition, nitrate-treated rats had higher PPAR-γ (mRNA: 1.78-fold, p = .016 and protein: 19%, p = .076), PGC1-α (mRNA: 1.69-fold, p = .012 and protein: 68%, p = .001), and UCP1 (mRNA: 2.50-fold, p = .001 and protein: 81%, p = .001) in gonadal adipose tissue. Nitrate also reduced adipocyte area by 35% (p = .054) and increased adipocyte density by 31% (p = .086). In conclusion, antiobesity effect of nitrate in female rats is associated with increased browning of gonadal adipose tissue as indicated by higher expression of PPAR-γ, PGC1-α, and UCP1 and reduced adipocyte area and increased adipocyte density.

Cigarette smoke is associated with up-regulation of inducible NOS and COX-2 protein expression and activity in granulosa cells of women undergoing in vitro fertilization

Cigarette smoke exposure represents a well-established ovotoxic exogenous stress, but the molecular mechanisms underlying of this effect are still unclear. Cigarette smoke upregulates inflammatory genes in the female reproductive organs, therefore an abnormal inflammation response may contribute to the impairment of female fertility. In this study we investigated for the first time the effect of cigarette smoke exposure on NOS and COX expression and activity and on their transcription factors (CREB and NF-kB) in human GCs and on the release of NO and PGE₂ in the FF in smoking and non-smoking patients undergoing IVF treatment. In addition, correlation analysis between AMH serum levels, an index of ovarian reserve, and smoking exposure or iNOS and COX-2 protein expression levels were performed using a Pearson correlation method. Cigarette smoke exposure resulted in a significant increase of iNOS and COX-2 protein expression together with an increase of iNOS activity and PGE₂ levels. pNF-kB and pCREB protein expression were upregulated in the GCs of smokers compared to non-smokers. The habit of smoking was negatively correlated with serum AMH levels, and positively correlated with iNOS and COX-2 protein expression levels. The data presented in the current study revealed a novel molecular mechanism underlying the toxic effects of cigarette smoke on fertility. Additional pathways mediating the effects of cigarette smoke exposure in human GCs cannot be excluded and should be investigated in future studies.

The Role of Nitric Oxide in Stem Cell Biology

Nitric oxide (NO) is a gaseous biomolecule endogenously synthesized with an essential role in embryonic development and several physiological functions, such as regulating mitochondrial respiration and modulation of the immune response. The dual role of NO in embryonic stem cells (ESCs) has been previously reported, preserving pluripotency and cell survival or inducing differentiation with a dose-dependent pattern. In this line, high doses of NO have been used in vitro cultures to induce focused differentiation toward different cell lineages being a key molecule in the regenerative medicine field. Moreover, optimal conditions to promote pluripotency in vitro are essential for their use in advanced therapies. In this sense, the molecular mechanisms underlying stemness regulation by NO have been studied intensively over the current years. Recently, we have reported the role of low NO as a hypoxia-like inducer in pluripotent stem cells (PSCs), which supports using this molecule to maintain pluripotency under normoxic conditions. In this review, we stress the role of NO levels on stem cells (SCs) fate as a new approach for potential cell therapy strategies. Furthermore, we highlight the recent uses of NO in regenerative medicine due to their properties regulating SCs biology.

Perchlorate, nitrate, and thiocyanate: Environmental relevant NIS-inhibitors pollutants and their impact on thyroid function and human health

Thyroid disruptors are found in food, atmosphere, soil, and water. These contaminants interfere with the thyroid function through the impairment of thyroid hormone synthesis, plasma transport, peripheral metabolism, transport into the target cells, and thyroid hormone action. It is well known that iodide uptake mediated by the sodium-iodide symporter (NIS) is the first limiting step involved in thyroid hormones production. Therefore, it has been described that several thyroid disruptors interfere with the thyroid function through the regulation of NIS expression and/or activity. Perchlorate, nitrate, and thiocyanate competitively inhibit the NIS-mediated iodide uptake. These contaminants are mainly found in food, water and in the smoke of cigarettes. Although the impact of the human exposure to these anions is highly controversial, some studies indicated their deleterious effects in the thyroid function, especially in individuals living in iodine deficient areas. Considering the critical role of thyroid function and the production of thyroid hormones for growth, metabolism, and development, this review summarizes the impact of the exposure to these NIS-inhibitors on thyroid function and their consequences for human health.

Activation of Ovarian Taste Receptors Inhibits Progesterone Production Potentially via NO/cGMP and Apoptotic Signaling

Taste receptors are not only expressed in the taste buds, but also in other nongustatory tissues, including the reproductive system. Taste receptors can be activated by various tastants, thereby exerting relatively physiologic functions. The aim of this study was to investigate the effects and potential mechanisms underlying ovarian taste receptor activation on progesterone production using saccharin sodium as the receptor agonist in a pseudopregnant rat model. Taste 1 receptor member 2 (TAS1R2) and taste 2 receptor member 31 (TAS2R31) were demonstrated to be abundantly expressed in the corpora lutea of rats, and intraperitoneal injection of saccharin sodium can activate both of them and initiate their downstream signaling cascades. The activation of these ovarian taste receptors promoted nitric oxide (NO) production via endothelial nitric oxide synthase (eNOS). NO production then increased ovarian cyclic guanosine 3',5'-monophosphate (cGMP) levels, which, in turn, decreased ovarian cyclic adenosine 3',5'-monophosphate levels. In addition, the activation of ovarian taste receptors induced apoptosis, possibly through NO and mitogen-activated protein kinase signaling. As a result, the activation of ovarian taste receptors reduced the protein expression of steroidogenesis-related factors, causing the inhibition of ovarian progesterone production. In summary, our data suggest that the activation of ovarian taste receptors inhibits progesterone production in pseudopregnant rats, potentially via NO/cGMP and apoptotic signaling.

Current Knowledge on the Multifactorial Regulation of Corpora Lutea Lifespan: The Rabbit Model

Simple Summary

Corpora lutea (CL) are temporary endocrine structures that secrete progesterone, which is essential for maintaining a healthy pregnancy. A variety of regulatory factors come into play in modulating the functional lifespan of CL, with luteotropic and luteolytic effects. Many aspects of luteal phase physiology have been clarified, yet many others have not yet been determined, including the molecular and/or cellular mechanisms that maintain the CL from the beginning of luteolysis during early CL development. This paper summarizes our current knowledge of the endocrine and cellular mechanisms involved in multifactorial CL lifespan regulation, using the pseudopregnant rabbit model.

Abstract

Our research group studied the biological regulatory mechanisms of the corpora lutea (CL), paying particular attention to the pseudopregnant rabbit model, which has the advantage that the relative luteal age following ovulation is induced by the gonadotrophin-releasing hormone (GnRH). CL are temporary endocrine structures that secrete progesterone, which is essential for maintaining a healthy pregnancy. It is now clear that, besides the classical regulatory mechanism exerted by prostaglandin E2 (luteotropic) and prostaglandin F2α (luteolytic), a considerable number of other effectors assist in the regulation of CL. The aim of this paper is to summarize our current knowledge of the multifactorial mechanisms regulating CL lifespan in rabbits. Given the essential role of CL in reproductive success, a deeper understanding of the regulatory mechanisms will provide us with valuable insights on various reproductive issues that hinder fertility in this and other mammalian species, allowing to overcome the challenges for new and more efficient breeding strategies.

Novel Insights on the Role of Nitric Oxide in the Ovary: A Review of the Literature

Nitric oxide (NO) is formed during the oxidation of L-arginine to L-citrulline by the action of multiple isoenzymes of NO synthase (NOS): neuronal NOS (nNOS), endotelial NOS (eNOS), and inducible NOS (iNOS). NO plays a relevant role in the vascular endothelium, in central and peripheral neurons, and in immunity and inflammatory systems. In addition, several authors showed a consistent contribution of NO to different aspects of the reproductive physiology. The aim of the present review is to analyse the published data on the role of NO within the ovary. It has been demonstrated that the multiple isoenzymes of NOS are expressed and localized in the ovary of different species. More to the point, a consistent role was ascribed to NO in the processes of steroidogenesis, folliculogenesis, and oocyte meiotic maturation in in vitro and in vivo studies using animal models. Unfortunately, there are few nitric oxide data for humans; there are preliminary data on the implication of nitric oxide for oocyte/embryo quality and in-vitro fertilization/embryo transfer (IVF/ET) parameters. NO plays a remarkable role in the ovary, but more investigation is needed, in particular in the context of human ovarian physiology.

Involvement of nitric oxide during in vitro oocyte maturation, sperm capacitation and in vitro fertilization in pig

The importance of porcine species for meat production is undeniable. Due to the genetic, anatomical, and physiological similarities with humans, from a biomedical point of view, pig is considered an ideal animal model for the study and development of new therapies for human diseases. The in vitro production (IVP) of porcine embryos has become widespread as a result of these qualities and there is significant demand for these embryos for research purposes. However, the efficiency of porcine embryo IVP remains very low, which hinders its use as a model for research. The high degree of polyspermic fertilization is the main problem that affects in vitro fertilization (IVF) in porcine species. Furthermore, oocyte in vitro maturation (IVM) is another important step that could be related to polyspermic fertilization and low embryo production. The presence of nitric oxide synthase (NOS), the enzyme that produces nitric oxide (NO), has been detected in the oviduct, the ovary, the oocyte and the sperm cell of porcine species. Its functions include regulating oviductal activity, ovulation, acquisition of meiotic competence, oocyte activation, sperm capacitation, and gamete interaction. Therefore, in this review, we summarize the current knowledge on the role of NO/NOS system in each of the steps that lead to the production of porcine embryos in an in vitro environment, i.e. IVM, sperm capacitation, IVF, and embryo culture. We also discuss the possible ways in which the NO/NOS system could be used to enhance IVP of porcine embryos.

What happens after a blood meal? A transcriptome analysis of the main tissues involved in egg production in Rhodnius prolixus, an insect vector of Chagas disease

The blood-sucking hemipteran Rhodnius prolixus is a vector of Chagas disease, one of the most neglected tropical diseases affecting several million people, mostly in Latin America. The blood meal is an event with a high epidemiological impact since adult mated females feed several times, with each meal resulting in a bout of egg laying, and thereby the production of hundreds of offspring. By means of RNA-Sequencing (RNA-Seq) we have examined how a blood meal influences mRNA expression in the central nervous system (CNS), fat body and ovaries in order to promote egg production, focusing on tissue-specific responses under controlled nutritional conditions. We illustrate the cross talk between reproduction and a) lipids, proteins and trehalose metabolism, b) neuropeptide and neurohormonal signaling, and c) the immune system. Overall, our molecular evaluation confirms and supports previous studies and provides an invaluable molecular resource for future investigations on different tissues involved in successful reproductive events. These analyses serve as a starting point for new investigations, increasing the chances of developing novel strategies for vector population control by translational research, with less impact on the environment and more specificity for a particular organism.

Physiological relevance of nitric oxide in ovarian functions: An overview

Nitric oxide (NO, nitrogen monoxide), a short-lived, free radical carrying an unpaired electron, is one of the smallest molecules synthesized in the biological system. In addition to its role in angiogenesis, neuronal function and inflammatory response, NO has wide-spread significance in regulation of ovarian function in vertebrates. Based on tissue-specific expression, three different nitric oxide synthase (NOS) isoforms, neuronal (nNOS) or NOS1, inducible (iNOS) or NOS2 and endothelial (eNOS) or NOS3 have been identified. While expression of both inducible (iNOS) and constitutive NOS (eNOS) isoforms varies considerably in the ovary at various stages of follicular growth and development, selective binding of NO with proteins containing heme moieties have significant influence on ovarian steroidogenesis. Besides, NO modulation of ovulatory response suggests physiological significance of NO/NOS system in mammalian ovary. Compared to the duality of NO action on follicular development, steroidogenesis and meiotic maturation in mammalian models, participation of NO/NOS system in teleost ovary is less investigated. Genes encoding nos1 and nos2 have been identified in fish; however, presence of nos3 is still ambiguous. Interestingly, two distinct nos2 genes, nos2a and nos2b in zebrafish, possibly arose through whole genome duplication. Differential expression of major NOS isoforms in catfish ovary, NO inhibition of meiosis resumption in Anabas testudineus follicle-enclosed oocytes and NO/sGC/cGMP modulation of oocyte maturation in zebrafish are some of the recent advancements. The present overview is an update on the advancements made and shortfalls still remaining in NO/NOS modulation of intercellular communication in teleost vis-à-vis mammalian ovary.

Therapeutic potential of sodium selenite in letrozole induced polycystic ovary syndrome rat model: Targeting mitochondrial approach (selenium in PCOS)

Polycystic ovary syndrome (PCOS) is the most common endorinopathy in fertile women with heterogeneous reproductive and metabolic phenotypes and unknown etiology. This study was undertaken to investigate the beneficial effect of selenium in management of letrozole induced PCOS and its role in modulating mitochondrial dynamics, and its associated signals. Twenty four adult female rats were enrolled and randomly divided into four equal groups; control group received 0.5% w/v carboxymethyl cellulose (CMC); PCOS group received letrozole (1 mg/kg, daily) in 0.5% CMC for 21 days. From day 22 to day 36, after letrozole PCOS induction, the (PCOS +Metformin) group received metformin (2 mg/kg, daily) while (PCOS + sodium selenite) group received sodium selenite (0.1 mg/kg, daily). All doses were given via oral gavage. At the study end, serum hormone levels, lipid profile and HOMA-IR were assessed. Ovaries were dissected, used for histopathological evaluation, immunohistochemical detection of B-cell lymphoma-2 (Bcl-2), and its associated X protein (Bax) expression, measurement of redox status, mitochondrial dynamics markers and citrate synthase (CS) activity. Furthermore Mitofusins 2 (Mfn2) and dynamin related protein 1 (Drp1) mRNA expression was assessed by real time PCR. Selenium treatment of PCOS rats succeeded, comparable to metformin, to greatly improve the PCOS associated endocrine and metabolic phenotypes and histopathological changes, mostly through modulating mitochondrial dynamics, anti-apoptotic action, alleviating oxidative stress and mitochondrial dysfunction. So, selenium could provide a novel therapeutic strategy for PCOS.

Effects of plane of nutrition and arginine on ovarian follicles in non-pregnant sheep: Cell proliferation, and expression of endothelial nitric oxide and its receptor

The aim of this study was to investigate the role of the nitric oxide (NO) system in ovarian function, by determining if arginine (Arg) supplementation impacts follicle number, cell proliferation, and expression of the NO system members in nutritionally compromised ewes. Ewes were randomly assigned into maintenance (C, 100% requirements), excess (O; 2xC), or restricted (U; 0.6xC) diets 8 weeks prior to Arg treatment. Ewes were individually fed twice daily with pelleted diets. Ewes from each nutritional group were randomly assigned to one of two treatments: saline or Arg, which was initiated on day 0 of the estrous cycle and administered 3 times per day. Ovaries were collected at the early-luteal, mid-luteal and late-luteal/follicular phases of the estrous cycle to determine 1) the number of surface follicles, 2) follicle cell proliferation marked by Ki67 protein expression, and 3) expression of endothelial nitric oxide (eNOS; NOS3) and soluble guanylyl cyclase beta (sGC; GUCY1B3) protein and mRNA in granulosa (G) and theca (T) layers using immunohistochemistry followed by image analysis and qPCR, respectively. During nutritional treatment, C maintained body weight, O gained 6±1.2 kg, and U lost 14±1.3 kg. Our data show that: 1) Ki67 was expressed in all ovarian compartments, eNOS protein was detected in blood vessels of T and stroma, and sGC protein was detected in T cells, and blood vessels of T layer and other ovarian compartments; 2) plane of nutrition affected the number of surface follicles, and thus folliculogenesis, cell proliferation in the T layer, eNOS and sGC protein expression in T, and NOS3 and GUCY1B3 mRNA expression in G; 3) Arg treatment affected cell proliferation in G and T, eNOS and sGC protein expression in T, mRNA expression of NOS3 in T in all groups, and GUCY1B3 in G depending on the stage of the estrous cycle; and 4) G and T cell proliferation, and expression of eNOS and sGC protein in T was affected by the stage of the estrous cycle. Our data demonstrated that plane of nutrition and Arg are involved in the regulation of follicular functions in non-pregnant sheep.

Nitrate: An Environmental Endocrine Disruptor? A Review of Evidence and Research Needs

Nitrate is heavily used as an agricultural fertilizer and is today a ubiquitous environmental pollutant. Environmental endocrine effects caused by nitrate have received increasing attention over the last 15 years. Nitrate is hypothesized to interfere with thyroid and steroid hormone homeostasis and developmental and reproductive end points. The current review focuses on aquatic ecotoxicology with emphasis on field and laboratory controlled in vitro and in vivo studies. Furthermore, nitrate is just one of several forms of nitrogen that is present in the environment and many of these are quickly interconvertible. Therefore, the focus is additionally confined to the oxidized nitrogen species (nitrate, nitrite and nitric oxide). We reviewed 26 environmental toxicology studies and our main findings are (1) nitrate has endocrine disrupting properties and hypotheses for mechanisms exist, which warrants for further investigations; (2) there are issues determining actual nitrate-speciation and abundance is not quantified in a number of studies, making links to speciation-specific effects difficult; and (3) more advanced analytical chemistry methodologies are needed both for exposure assessment and in the determination of endocrine biomarkers.

Diethylstilbestrol administration inhibits theca cell androgen and granulosa cell estrogen production in immature rat ovary

Diethylstilbestrol (DES), a strong estrogenic compound, is well-known to affect the reproductive system. In this study, we investigated the effects of DES administration on gonadotropin levels and ovarian steroidogenesis in prepubertal rats. DES treatment acutely reduced serum LH levels, followed by a reduction in the expression of various steroidogenesis-related genes in theca cells. Serum FSH levels were almost unaffected by DES-treatment, even though Cyp19a1 expression was markedly reduced. Serum progesterone, testosterone and estradiol levels were also declined at this time. LH levels recovered from 12 h after DES-treatment and gradually increased until 96 h with a reduction of ERα expression observed in the pituitary. Steroidogenesis-related genes were also up-regulated during this time, except for Cyp17a1 and Cyp19a1. Consistent with observed gene expression pattern, serum testosterone and estradiol concentrations were maintained at lower levels, even though progesterone levels recovered. DES-treatment induced the inducible nitric oxide synthase (iNOS) in granulosa cells, and a nitric oxide generator markedly repressed Cyp19a1 expression in cultured granulosa cells. These results indicate that DES inhibits thecal androgen production via suppression of pituitary LH secretion and ovarian Cyp17a1 expression. In addition, DES represses Cyp19a1 expression by inducing iNOS gene expression for continuous inhibition of estrogen production in granulosa cells.

Histological analysis of arteriovenous anastomosis-like vessels established in the corpus luteum of cows during luteolysis

Background

The mechanisms regulating the function and regression of the corpus luteum (CL) have not yet been elucidated in detail. The regressed CL of cows was previously reported to be filled with unusual vessels like arteriovenous anastomosis (AVA); however how these vessels are being established during luteolysis remains unknown.

Methods

The bovine CL at different luteal stages and regressing bovine CL induced by prostaglandin F_2α (PGF) were histologically analyzed using light and electron microscopic levels. The changes in mRNA expression of genes encoding α-smooth muscle actin (SMA; Acta2) and transforming growth factor β1 (Tgfb1) in luteal tissues were analyzed by quantitative RT-PCR.

Results

AVA-like vessels appeared in the regressed CL with a diameter less than 1.5 cm in which no functional luteal cells and macrophages were observed. Epithelioid cells in the AVA-like vessel wall were immunoreactive for SMA, and the lumen of the vessels were narrow. Immunoreaction for SMA was found in the tunica media of typical arteries and arterioles, and pericytes around capillary vessel. Cells with elongated cytoplasmic processes ―resident fibroblasts expressing vimentin― distributed in the CL parenchyma without any association with blood vessels are also immunoreactive for SMA, and accumulated around arteries and arterioles during the late-luteal stage. In the regressed CL, walls of arteries and arterioles consisted of more than two layers of epithelioid cells positive for both SMA and desmin, suggesting that they are myofibroblasts transformed from fibroblasts. The percentage of the area positive for SMA and the mRNA expression of Acta2 were significantly increased in the regressed CL; however, they did not alter when a luteolytic dose of PGF was injected in vivo and collected within 24 h after the injection. On the other hand, Tgfb1, a known regulator for myofibroblast transformation, was significantly increased in PGF-induced regressing CL as well as in the CL during the late-luteal stage.

Conclusions

SMA-positive myofibroblasts accumulates around the arteries and arterioles to form AVA-like vessels during luteolysis in cows. PGF indirectly regulates myofibroblast transformation through enhancing the expression of TGFβ1. These peculiar AVA-like vessels may be involved in the regulation of blood flow in the bovine CL during luteolysis.

Effect of dystocia on some hormonal and biochemical parameters in the one-humped camel (Camelus dromedarius)

The present study compared some of the hormonal and biochemical constituents of serum from eutocic and dystocic one-humped camels (Camelus dromedarius). Sera were harvested from eutocic (n = 9) and dystocic (n = 20) camels within the first 15 minutes after delivery. Although there were no differences in the concentrations of estradiol-17β (E2) and prostaglandin F2α (PGF2α) between the eutocic and the dystocic animals, the level of progesterone (P4) and cortisol was significantly higher (P < 0.01) in animals that experienced dystocia than those that had a normal birth. There were no differences between the concentrations of alkaline phosphatase, aspartate aminotransferase, calcium, cholesterol, creatine kinase, creatinine, or magnesium (Mg) in eutocic and dystocic animals. The nitric oxide concentration was significantly higher (P < 0.01) in the serum from animals with dystocia than those that had normal births. By contrast, the serum concentrations of glucose, phosphorus (P), and triglycerides were significantly lower (P < 0.01) in eutocic camels compared with dystocic camels. As the delayed decline of P4 is reported to be the major hormonal difference between eutocic and dystocic camels, we propose that the insensitivity of corpus luteum to luteolytic action may be a cause of dystocia. Moreover, stress and hormonal changes may affect the metabolic traits in dystocia camels.

Nitric oxide synthase (NOS) inhibition during porcine in vitro maturation modifies oocyte protein S-nitrosylation and in vitro fertilization

Nitric oxide (NO) is a molecule involved in many reproductive processes. Its importance during oocyte in vitro maturation (IVM) has been demonstrated in various species although sometimes with contradictory results. The objective of this study was to determine the effect of NO during IVM of cumulus oocyte complexes and its subsequent impact on gamete interaction in porcine species. For this purpose, IVM media were supplemented with three NOS inhibitors: NG-nitro-L-arginine methyl ester (L-NAME), NG-monomethyl-L-arginine (L-NMMA) and aminoguanidine (AG). A NO donor, S-nitrosoglutathione (GSNO), was also used. The effects on the cumulus cell expansion, meiotic resumption, zona pellucida digestion time (ZPdt) and, finally, on in vitro fertilization (IVF) parameters were evaluated. The oocyte S-nitrosoproteins were also studied by in situ nitrosylation. The results showed that after 42 h of IVM, AG, L-NAME and L-NMMA had an inhibitory effect on cumulus cell expansion. Meiotic resumption was suppressed only when AG was added, with 78.7% of the oocytes arrested at the germinal vesicle state (P<0.05). Supplementation of the IVM medium with NOS inhibitors or NO donor did not enhance the efficiency of IVF, but revealed the importance of NO in maturation and subsequent fertilization. Furthermore, protein S-nitrosylation is reported for the first time as a pathway through which NO exerts its effect on porcine IVM; therefore, it would be important to determine which proteins are nitrosylated in the oocyte and their functions, in order to throw light on the mechanism of action of NO in oocyte maturation and subsequent fertilization.

Interrelationship between NO and androgenic activity in mice, Mus musculus, following temporal phase relation of serotonergic and dopaminergic neural oscillations

The present study was designed to monitor the correlation of gonadal steroidogenic activity and nitric oxide (NO) of plasma and testis of male laboratory mouse, Mus musculus, under (1) control/basal and (2) experimental conditions. In the first study, male mice (n = 6) of three age groups (3-week-old sexually immature, 9-week-old sexually mature and 1.5-year-old) were assayed for plasma testosterone and level of NO in the plasma and testis. The immunoreactivity of 3-β-hydroxysteroid dehydrogenase (3-β-HSD) and androgen receptors (ARs) was also detected in testis and epididymis, respectively. In the second study, the reproductive state of mice was altered by injecting precursors of serotonin 5-hydroxytryptophan (5-HTP) and dopamine L-dihydroxyphenylalanine (L-DOPA) daily for 13 days. In one subgroup, mice received their daily injections 8 h apart and in another subgroup 12 h apart. A third subgroup of control mice received two daily injections of normal saline. After the completion of the experiment, the mentioned parameters were measured. The results showed a significant increase in levels of NO and a lowering of the immune reactivity of 3-β-HSD and AR, in both leydig cells and the epididymis in the sexually immature, old-age mice as well as in the mice that received 5-HTP and L-DOPA in the 8-h temporal relation, whereas opposite effects were observed in the sexually mature mice as well as in the mice that received 5-HTP and L-DOPA in the 12-h temporal relation. These findings led us to conclude that an inverse correlation exists between testicular steroidogenic activity and NO activity of laboratory mice under control and experimentally modulated gonadal conditions.

Essential actions of melatonin in protecting the ovary from oxidative damage

Free radicals and other reactive species are involved in normal ovarian physiology. However, they are also highly reactive with complex cellular molecules (proteins, lipids, and DNA) and alter their functions leading to oxidative stress. Oxidative damage may play a prominent role in the development of disorders that considerably influence female fertility. Melatonin, because of its amphiphilic nature that allows for crossing morphophysiological barriers, is an effective antioxidant for protecting macromolecules against oxidative stress caused by reactive species. The balance between reactive oxygen species and antioxidants within the follicle seems to be critical to the function of the oocyte and granulosa cells and evidence has accumulated showing that melatonin is involved in the protection of these cells. Melatonin appears to have varied functions at different stages of follicle development, oocyte maturation, and luteal stage. Melatonin concentration in the growing follicle may be an important factor in avoiding atresia, because melatonin in the follicular fluid reduces apoptosis of critical cells. Melatonin also has protective actions during oocyte maturation reducing intrafollicular oxidative damage. An association between melatonin concentrations in follicular fluid and oocyte quality has been reported; this would allow a preovulatory follicle to fully develop and provide a competent oocyte for fertilization. The functional role of reactive species and the cytoprotective properties of melatonin on the ovary from oxidative damage are summarized in this brief review.

Endometritis impairs luteal development, function, and nitric oxide and ascorbic acid concentrations in buffalo (Bubalus bubalis)

A vast majority of the world buffalo resource is concentrated in tropical and subtropical countries. Apart from heat stress and poor nutritional availability, endometritis is one of the most commonly encountered reproductive problems limiting fertility and consequently productive potential of the species. As demonstrated recently, endometritis impairs growth and follicular fluid composition of the largest follicle in buffalo. In the present study, the effect of endometritis on luteal development, function, nitric oxide (NO), and ascorbic acid was investigated. Reproductive tracts were collected from 90 cyclic buffaloes at an abattoir and grouped into endometritic (n = 36) or non-endometritic (n = 54) buffaloes based on physical examination of uterine mucus, white side test, and uterine cytology. Samples with pus-containing mucus, positive reaction on white side test, and/or >5 % neutrophils were considered to be positive for endometritis. Corpora lutea were enucleated, weighed, classified into stages I to IV, and assayed for progesterone (P(4)), NO, and ascorbic acid concentrations. Endometritic buffaloes had lesser (P < 0.0001) luteal weight and P(4), NO, and ascorbic acid concentrations than non-endometritic buffaloes. The findings indicated that endometritis impairs corpus luteum development and function in buffalo. Reduced luteal NO and ascorbic acid concentrations during endometritis are novel findings.

Influence of nitric oxide on in vitro growth, survival, steroidogenesis, and apoptosis of follicle stimulating hormone stimulated buffalo (Bubalus bubalis) preantral follicles

Effect of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on in vitro survival, growth, steroidogenesis, and apoptosis of buffalo preantral follicles (PFs) was investigated. PFs (200~250 µm) were isolated by micro-dissection and cultured in 0 (control), 10^-3, 10^-5, 10^-7, and 10^-9 M SNP. To examine the reversible effect of SNP, PFs were cultured with 10^-5 M SNP + 1 mM N^ω-nitro-L-arginine methyl ester (L-NAME) or 1.0 µg hemoglobin (Hb). The results showed that greater concentrations of SNP (10^-3, 10^-5, 10^-7 M) inhibited (p < 0.05) FSH-induced survival, growth, antrum formation, estradiol production, and oocyte apoptosis in a dose-dependent manner. However, a lower dose of SNP (10^-9 M) significantly stimulated (p < 0.05) the survival, growth, antrum formation, follicular oocyte maturation, and stimulated progesterone secretion compared to the control. A combination of SNP + L-NAME promoted the inhibitor effect of SNP while a SNP + Hb combination reversed this effect. Nitrate and nitrite concentrations in the culture medium increased (p < 0.05) in a dose-dependent manner according to SNP concentration in the culture medium. At higher concentrations, SNP had a cytotoxic effect leading to follicular oocyte apoptosis whereas lower concentrations have stimulatory effects. In conclusion, NO exerts a dual effect on its development of buffalo PFs depending on the concentration in the culture medium.

Mechanistic links between oxidative/nitrosative stress and tumor necrosis factor alpha in letrozole-induced murine polycystic ovary:

This study aimed to investigate the possible relationship between ovarian functionality and the oxidative response during cystogenesis induced by hyperandrogenization with letrozole and examine protective effect of the peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist, pioglitazone (PIO), in polycystic ovary (PCO). Ovarian cysts were induced by oral administration of letrozol (1 mg/kg/day) for 21 consecutive days in the female rats. Effective dose of PIO (20 mg/kg/day) was administrated orally for 21 days. Serum estradiol (E), progesterone (P), testosterone (T), and the ovarian immunomodulator prostaglandin E (PGE) were analyzed as biomarkers of ovarian function. To determine the role of oxidative stress in PCO, the level of cellular lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and peroxynitrite (ONOO), and tumor necrosis factor alpha (TNF-α) as a marker of inflammation and apoptosis were measured in serum and the ovaries. Letrozole-induced PCO in rats exhibited a significant increase in LPO and ONOO in serum and ovary while significantly decreased serum and ovarian SOD, CAT, and GPx. Serum T and TNF-α, and ovarian PGE were increased in animals with cysts compared with healthy controls, while E and P diminished. When compared to control group, letrozole-treated group showed irregular sexual cycles, polycystic ovaries characterized by high incidence of sub-capsular ovarian cyst with diminished or scant granulosa cell layer, increased number of atretic pre-antral and antral follicles and absence of corpus luteum. There were almost no primary, secondary, and tertiary follicles observed in PCO rats. All measured parameters were improved by PIO and reached close to normal levels. The present study further supports the role of oxidative/nitrosative stress and infiammatory responses in the pathogenesis of letrozole-induced hyperandrogenic PCO rats. Results indicate that PIO is able to exert direct antioxidative and anti-inflammatory effects on the endocrine, biochemical, and pathological alterations independent of its possible effects mediated via increased insulin sensitivity in hyperandrogenized PCO.

Effects of capsaicin on nitric oxide synthase isoforms in prepubertal rat ovary

Nitric oxide (NO) has emerged as an important intra-ovarian regulatory factor. We investigated effects of low dose capsaicin (CAP) treatment on the different NOS isoforms in prepubertal rat ovaries. Fifteen 21-day-old female Sprague-Dawley rats were divided randomly into three groups. The first group received no treatment, the second group received 0.5 mg/kg/day CAP dissolved in the vehicle, and the third group was treated with the vehicle only. The animals were euthanized by ether inhalation after 15 days and their ovaries were excised. Ovaries were fixed in 10% neutral buffered formalin and embedded in paraffin. Sections were processed for standard immunohistochemistry using the labeled streptavidin-biotin technique for expression of nNOS, eNOS and iNOS. We demonstrated that CAP induced expression of NOS isotypes including eNOS, iNOS and nNOS in prepubertal rat ovaries. CAP may lead to release of NO either directly from nerves or indirectly by evoking release from other cells via the action of neuropeptides that are released from afferent terminals and are involved in regulating female reproductive function.

Regulation of inducible nitric oxide synthase expression in bovine ovarian granulosa cells

Nitric oxide (NO) is a potential regulator of ovarian follicle growth, and ovarian granulosa cells reportedly generate NO in response to gonadotrophins, suggesting that the regulated form of nitric oxide synthase (iNOS) is present. The objectives of the present study were to gain insight into the expression and role of iNOS in the follicle. Messenger RNA encoding iNOS was detected in granulosa cells, and abundance was higher in growing dominant follicles compared to subordinate follicles (P<0.01). FSH (P<0.05) and IGF1 (P<0.01) stimulated oestradiol secretion and iNOS mRNA abundance in granulosa cells in vitro, whereas FGF2 (P<0.05) and EGF (P<0.01) decreased oestradiol secretion and iNOS expression. The addition of an anti-oestrogen prevented FSH-induced iNOS mRNA accumulation. Inhibition of endogenous NO production did not affect steroidogenesis in granulosa cells, but increased FasL mRNA abundance, caspase-3 activation and the incidence of apoptotic cell death (P<0.05). These results demonstrate that iNOS is expressed in ruminant granulosa cells and is regulated by gonadotrophins and oestradiol. Physiological levels of NO may contribute to the survival of granulosa cells.

Nitric oxide inhibits ACTH-induced cortisol production in near-term, long-term hypoxic ovine fetal adrenocortical cells

We previously reported that in the sheep fetus, long-term hypoxia (LTH) resulted in elevated basal plasma adrenocorticotropic hormone (ACTH(1- 39)) whereas the cortisol levels were not different from normoxic controls. We also showed that LTH enhances endothelial nitric oxide synthase (eNOS) expression in the fetal adrenal. This study was designed to determine the effect of NO on cortisol production in adrenocortical cells from LTH fetal sheep. Ewes were maintained at high altitude (3820 m) from ∼40 days' gestation (dG) to near term. Between 138 and 141 dG, fetal adrenal glands were collected from LTH and age-matched normoxic control fetuses. Adrenal cortical cells were pretreated with sodium nitroprusside (SNP), nitro-L-arginine methyl ester (L-NAME), L-arginine, or diethyleneamine NO (DETA-NO) and then challenged with 10 nmol/L ACTH. Cortisol responses were compared after 1 hour. Adrenocorticotropic hormone -induced cortisol secretion was significantly higher in LTH versus control (P < .01). Enhancement of NO with L-arginine resulted in a significant reduction of ACTH-mediated cortisol production in the LTH group. DETA-NO also caused a significant decrease in ACTH-mediated cortisol production (P < .05). Inhibition of NOS with L-NAME significantly increased cortisol production in the LTH group (P < .05 compared to ACTH alone), whereas the effect on the control group was not significant. Nitric oxide synthase activity was significantly higher in the LTH group compared to control, but this difference was eliminated following ACTH treatment. These data indicate that LTH enhances adrenal cortical sensitivity to the inhibitory effects of NO on cortisol production. Nitric oxide may, therefore, play an important role in regulating ACTH-induced cortisol production in the LTH fetal adrenal.

Effects and mechanisms of nonylphenol on corticosterone release in rat zona fasciculata-reticularis cells

Alkylphenol ethoxylate, consisting of ∼80% nonylphenol ethoxylate (NPEO), is a major group of nonionic surfactant. The primary degradation product of NPEO, nonylphenol (NP), interferes with reproduction, induces cell death in gonads, and leads to changes in other reproductive parameters. With such apparent stress, NP is believed to induce stress response mechanism, i.e., adrenal cortical hormone. However, the effects and action mechanisms of NP on rat adrenal zona fasciculata-reticularis (ZFR) cells are still unclear. This study explored the effects of NP on corticosterone release. ZFR cells were incubated with NP in the presence or absence of adrenocorticotropin (ACTH), 8-bromo-cyclic 3',5'-adenosine monophosphate (8-Br-cAMP), forskolin (FSK), 25-hydroxyl cholesterol (25-OH-cholesterol), pregnenolone, progesterone, or deoxycorticosterone at 37°C for 1 h. The concentrations of corticosterone or pregnenolone in the spent media were measured by radioimmunoassay. The expressions of steroidogenic acute regulatory (StAR) protein, cytochrome P450 side-chain cleavage (P450scc) protein, and 11β-hydroxylase in the cells were measured by Western blot. The data demonstrated that (1) NP stimulated corticosterone release induced by ACTH, 8-Br-cAMP, FSK, 25-OH-cholesterol, pregnenolone, progesterone, or deoxycorticosterone; (2) NP significantly increased pregnenolone release in the control, 25-OH-cholesterol, trilostane, and 25-OH-cholesterol + trilostane groups; (3) NP-stimulated corticosterone release was estrogen receptor dependent, but mediated by nitric oxide and p38 mitogen-activated protein kinase pathway independent; and (4) NP did not affect StAR, 11β-hydroxylase, or P450scc protein expression. These results suggest that NP acts directly on rat ZFR cells to stimulate corticosterone release and that the stimulation mechanism of NP mediates through post-cAMP corticosterone manufacture enzymes, i.e., P450scc and 11β-hydroxylase.

Long-term hypoxia increases endothelial nitric oxide synthase expression in the ovine fetal adrenal

This study was designed to test the hypothesis that fetal adrenal nitric oxide synthase (NOS) is elevated in response to long-term hypoxia (LTH). Pregnant ewes were maintained at high altitude (3820 m) for approximately the last 100 days of gestation. Between days 138 and 141 of gestation, adrenal glands were collected from LTH fetuses and age-matched normoxic controls. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western analysis were used to quantify NOS expression, and NOS distribution was examined by immunohistochemistry and double-staining immunofluorescence for endothelial NOS (eNOS) and 17alpha-hydroxylase (CYP17). Neuronal NOS (nNOS) was expressed at very low levels and with no differences between groups. Expression of eNOS was significantly greater in the LTH group compared with control. Neuronal NOS was distributed throughout the cortex while the greatest density of eNOS was observed in the zona fasciculata/reticularis area and eNOS co-localized with CYP17. We conclude that LTH enhances eNOS expression in the inner adrenal cortex which may play a role in regulation of cortisol biosynthesis in the LTH fetus.

The phytoestrogen quercetin impairs steroidogenesis and angiogenesis in swine granulosa cells in vitro

Experimental evidence documents that nutritional phytoestrogens may interact with reproductive functions but the exact mechanism of action is still controversial. Since quercetin is one of the main flavonoids in livestock nutrition, we evaluated its possible effects on cultured swine granulosa cell proliferation, steroidogenesis, and redox status. Moreover, since angiogenesis is essential for follicle development, the effect of the flavonoid on Vascular Endothelial Growth Factor output by granulosa cells was also taken into account. Our data evidence that quercetin does not affect granulosa cell growth while it inhibits progesterone production and modifies estradiol 17beta production in a dose-related manner. Additionally, the flavonoid interferes with the angiogenic process by inhibiting VEGF production as well as by altering redox status. Since steroidogenesis and angiogenesis are strictly involved in follicular development, these findings appear particularly relevant, pointing out a possible negative influence of quercetin on ovarian physiology. Therefore, the possible reproductive impact of the flavonoid should be carefully considered in animal nutrition.

Prostaglandin F(2alpha) regulates the nitric oxide generating system in bovine luteal endothelial cells

The objective of the present study was to elucidate whether luteolytic prostaglandin F(2alpha) (PGF) plays roles in regulating the nitric oxide (NO) generating system in luteal endothelial cells (LECs). Reverse transcriptase PCR, immunoblotting and immunostaining revealed the presence of PGF receptor mRNA (521 bp) and protein (64 kDa) in cultured LECs obtained from the mid-stage corpus luteum. When cultured LECs were exposed to 0.1 microM-10 microM PGF, NO production was significantly stimulated by PGF at 24 h. When LECs were exposed to 1 microM PGF for 2, 6 and 24 h, PGF did not affect the expressions of endothelial NO synthase (eNOS) mRNA and protein. On the other hand, PGF stimulated the expression of inducible NOS (iNOS) mRNA (P<0.05) and protein (P<0.05) at 2 h, but not at 6 and 24 h. By observing the conversion of [(3)C](L)-arginine to [(3)C](L)-citrulline, we found that PGF stimulated NOS activity in cultured LECs at 2 h (P<0.05). The overall findings indicate that bovine LECs are a target for PGF and that PGF stimulates iNOS expression and NOS activity in bovine LECs. Stimulation of the NO generating system and NOS activity by PGF may result in increasing local NO production followed by luteolysis.

The role of nitric oxide in female reproduction

The cardiovascular system undergoes profound changes during pregnancy. Maternal intravascular volume begins to increase in the first trimester rising an average of 45% by term.1Cardiac output increases similarly2and is redistributed to organs whose functions are crucial for a successful pregnancy. In the guinea pig, uterine artery (UA) blood flow increases 3500%, while mesenteric and renal artery blood flows increase only 90% and 10% respectively.3Blood flow to the trunk actually diminishes. The mechanism underlying this redistribution is unknown. Coupled with the rise in cardiac output is a decrease in the systemic pressor response to angiotensin II (AII), norepinephrine(NE), and epinephrine.4–8There is also a decrease in the contraction response among some but not all vascular beds. For example, contraction of UA to NE and thromboxane is characteristically reduced by pregnancy, whereas the response of the carotid artery is unaltered8–10Since pregnancy does not alter neuroeffector mechanisms of NE such as release, receptor sensitivity, and accumulation11, changes in sympathetic control during pregnancy must be dependent on alterations at sites other than the neuroeffector junction. We have hypothesized that the mechanisms which alter vascular reactivity during pregnancy also mediate the redistribution of maternal cardiac output.9We have further hypothesized that many of these mechanisms involve endothelium-dependent factors which are modulated by sex hormones.

Follicular fluid nitric oxide (NO) concentrations in stimulated cycles: the relationship to embryo grading

OBJECTIVE

The microenvironment of the ovarian follicle is vital for normal oocyte development, folliculogenesis, and timely ovulation. We investigated the concentration of nitric oxide (NO) in follicular fluid, collected during oocyte retrieval after in-vitro fertilization and embryo transfer (IVF-ET) and its relationship to oocyte and embryo grading.

METHODS

A total of 53 follicular fluid samples were obtained from 15 patients undergoing IVF-ET program, oocyte retrieval by transvaginal guidance was per formed approximately 34-35 h after the hCG administration in stimulated cycles. Using a modified grading system the samples were divided in Group 1 with very few fragments in the cytoplasm with equal size blastomeres (best embryos) and Group 2 with significant or severe fragmentation or blastomeres of distinctively unequal size. Follicular NO was measured as nitrite/nitrate.

RESULTS

The mean concentration of NO follicular fluid is significantly higher in Group 2 than in Group 1 (57.54 +/- 12.67 nmol/mg vs. 42.43 +/- 16.32 nmol/mg). Using the correlation analysis, we observed a direct correlation between follicular NO and embryo grading (r = 0.61; P < 0.001) and an inverse correlation between follicular NO and serum 17beta-estradiol (r = -0.28; P < 0.05).

CONCLUSIONS

High levels of NO in human follicles may be detrimental. The inverse correlation found between NO and serum concentrations of 17beta-estradiol may be explained as a regulation of estradiol on maturation process of the oocytes and embryos in stimulated cycles through NO mediation.

Role of vasoactive substances on endometrial and ovarian function

In this review, it is proposed that the vasoactive agents endothelin (ET), nitric oxide (NO)/NO synthase (NOS) and carbon monoxide(CO)/heme oxygenase(HO) act directly on human endometrial functions and on ovarian functions in the normal menstrual cycle and in implantation periods. These vasoactive substances are likely to be important autocrine/paracrine factors that regulate a variety of physiological and pathological processes. The main actions of these agents are differentiation and implantation in the endometrial functions, and follicular growth, luteinization and atresia in the ovarian functions, in the tight connection between endometrial and ovarian systems during normal menstrual periods and during implantation (Reprod Med Biol 2007; 6: 157-164).

Amino acid, ammonia and urea concentrations in human pre-ovulatory ovarian follicular fluid

BACKGROUND

This study aimed to determine amino acid (AA), ammonia and urea concentrations in human ovarian follicular fluid and to compare these concentrations with those in the circulation.

METHODS

Samples of pre-ovulatory follicular fluid and peripheral venous blood were obtained from 14 IVF patients. High-performance liquid chromatography (HPLC) measurements of 25 AAs were the main outcome measures.

RESULTS

There was a significant gradient of most AAs from plasma to follicular fluid, with the exception of glutamate, which demonstrated a three-fold increase in follicular fluid concentration (70.0 +/- 3.80 microM) compared with plasma (23.18 +/- 2.20 microM; P < 0.001). The plasma-to-follicular fluid concentration difference for glutamine (81.83 +/- 9.2 microM) was greatest among all AAs. Among essential AAs, this difference was greatest for the branched-chain AAs, isoleucine, leucine and valine. Ammonia concentrations in follicular fluid and blood were 38.87 +/- 2.23 and 22.11 +/- 1.96 microM, respectively (P < 0.001). Urea concentration in follicular fluid was 3.37 +/- 0.18 mM, a value not significantly different from plasma concentration (3.36 +/- 0.22 mM; P = 0.911).

CONCLUSIONS

These plasma-follicular fluid differences may reflect both the utilization of AAs and the transport characteristics of the follicular cells. There is accumulation of glutamate and ammonia in pre-ovulatory follicular fluid. The data for urea are consistent with transport by passive diffusion, with no evidence of an active urea cycle in the cells of the follicle.

Characterization of L-arginine transport in adrenal cells: effect of ACTH

Nitric oxide synthesis depends on the availability of its precursor L-arginine, which could be regulated by the presence of a specific uptake system. In the present report, the characterization of the L-arginine transport system in mouse adrenal Y1 cells was performed. L-arginine transport was mediated by the cationic/neutral amino acid transport system y+L and the cationic amino acid transporter (CAT) y+ in Y1 cells. These Na+-independent transporters were identified by their selectivity for neutral amino acids in both the presence and absence of Na+ and by the effect of N-ethylmaleimide. Transport data correlated to expression of genes encoding for CAT-1, CAT-2, CD-98, and y+LAT-2. A similar expression profile was detected in rat adrenal zona fasciculata. In addition, cationic amino acid uptake in Y1 cells was upregulated by ACTH and/or cAMP with a concomitant increase in nitric oxide (NO) production.

Water quality influences reproduction in female mosquitofish (Gambusia holbrooki) from eight Florida springs

Contamination of freshwater ecosystems with nitrate is a growing global concern. Although nitrate pollution is recognized as a cause of aquatic eutrophication, few studies have examined the possible physiological impacts of nitrate exposure. In this study, we surveyed several reproductive variables of viviparous female Gambusia holbrooki (Poeciliidae) captured from eight springs in Florida. The eight springs represent a gradient of nitrate contamination (1-5 mg/L nitrate-nitrogen). We had two objectives in this study: to describe reproductive biology of female mosquitofish in the springs and to understand reproductive variation in the context of water quality, particularly the nitrate concentration. Our data show a significant negative association between nitrate and both dry weight of developing embryos and rate of reproductive activity among mature females. In addition, variation in Gambusia condition index and embryo number and dry weight was related to temperature variation, and hepatic weight was negatively related to dissolved oxygen concentration. Finally, we observed that many of the measured reproductive variables were interrelated and changeable, depending on gestational stage. Specifically, we provide evidence that maternal support of the embryo occurs at least during the first two thirds of gestation and that female fecundity is affected by an apparent tradeoff between embryo size and embryo number.

Fundamental roles of reactive oxygen species and protective mechanisms in the female reproductive system

Controlled oxidation, such as disulfide bond formation in sperm nuclei and during ovulation, plays a fundamental role in mammalian reproduction. Excess oxidation, however, causes oxidative stress, resulting in the dysfunction of the reproductive process. Antioxidation reactions that reduce the levels of reactive oxygen species are of prime importance in reproductive systems in maintaining the quality of gametes and support reproduction. While anti-oxidative enzymes, such as superoxide dismutase and peroxidase, play a central role in eliminating oxidative stress, reduction-oxidation (redox) systems, comprised of mainly glutathione and thioredoxin, function to reduce the levels of oxidized molecules. Aldo-keto reductase, using NADPH as an electron donor, detoxifies carbonyl compounds resulting from the oxidation of lipids and proteins. Thus, many antioxidative and redox enzyme genes are expressed and aggressively protect gametes and embryos in reproductive systems.

Relationship between cytokines and the embryotoxicity of hydrosalpingeal fluid

OBJECTIVE

The exact chemical composition of hydrosalpingeal fluid is unknown. The objective of this study was to characterize cytokines in hydrosalpingeal fluid (HSF) and examine their possible role in the embryo development.

STUDY DESIGN

HSF was aspirated at laparoscopic salpingectomy in eight infertile women. Levels of IL-1beta, IL-13, IL-8, IL-6 and TNF-alpha in the HSF were determined by quantitative immunoassay kits. Two-cell mouse embryos were incubated with 0, 25, 50 and 75% concentrations of HSF. The blastocyst development rate (BDR) of mouse embryos was measured at each HSF concentration.

RESULT(S)

The embryotoxicity of HSF was concentration dependent. An increase in the HSF concentration resulted in significant decrease in % BDR (p < 0.01). IL-1beta was present in six of the eight HSF samples with a mean (+/-SD) concentration of 0.9 +/- 0.8 pg/mL. IL-13 was not detected in any of the HSF samples. IL-8, IL-6 and TNF-alpha were detected in all samples with a mean (+/-SD) concentration of 4741.2 +/- 6554.4 pg/mL, 204.8+/-132.8 pg/ml and 12 +/- 12.8 pg/mL respectively. IL-6 was positively correlated with BDR (r = 0.53; p < 0.04).

CONCLUSION(S)

We demonstrated for the first time the presence of IL-1beta, IL-8, IL-6 and TNF-alpha and the absence of IL-13 in human hydrosalpingeal fluid. IL-6 was positively related to the BDR.

Role of oxidative stress in female reproduction

In a healthy body, ROS (reactive oxygen species) and antioxidants remain in balance. When the balance is disrupted towards an overabundance of ROS, oxidative stress (OS) occurs. OS influences the entire reproductive lifespan of a woman and even thereafter (i.e. menopause). OS results from an imbalance between prooxidants (free radical species) and the body's scavenging ability (antioxidants). ROS are a double-edged sword - they serve as key signal molecules in physiological processes but also have a role in pathological processes involving the female reproductive tract. ROS affect multiple physiological processes from oocyte maturation to fertilization, embryo development and pregnancy. It has been suggested that OS modulates the age-related decline in fertility. It plays a role during pregnancy and normal parturition and in initiation of preterm labor. Most ovarian cancers appear in the surface epithelium, and repetitive ovulation has been thought to be a causative factor. Ovulation-induced oxidative base damage and damage to DNA of the ovarian epithelium can be prevented by antioxidants. There is growing literature on the effects of OS in female reproduction with involvement in the pathophysiology of preeclampsia, hydatidiform mole, free radical-induced birth defects and other situations such as abortions. Numerous studies have shown that OS plays a role in the pathophysiology of infertility and assisted fertility. There is some evidence of its role in endometriosis, tubal and peritoneal factor infertility and unexplained infertility. This article reviews the role OS plays in normal cycling ovaries, follicular development and cyclical endometrial changes. It also discusses OS-related female infertility and how it influences the outcomes of assisted reproductive techniques. The review comprehensively explores the literature for evidence of the role of oxidative stress in conditions such as abortions, preeclampsia, hydatidiform mole, fetal embryopathies, preterm labour and preeclampsia and gestational diabetes. The review also addresses the growing literature on the role of nitric oxide species in female reproduction. The involvement of nitric oxide species in regulation of endometrial and ovarian function, etiopathogenesis of endometriosis, and maintenance of uterine quiescence, initiation of labour and ripening of cervix at parturition is discussed. Complex interplay between cytokines and oxidative stress in the etiology of female reproductive disorders is discussed. Oxidant status of the cell modulates angiogenesis, which is critical for follicular growth, corpus luteum formation endometrial differentiation and embryonic growth is also highlighted in the review. Strategies to overcome oxidative stress and enhance fertility, both natural and assisted are delineated. Early interventions being investigated for prevention of preeclampsia are enumerated. Trials investigating combination intervention strategy of vitamin E and vitamin C supplementation in preventing preeclampsia are highlighted. Antioxidants are powerful and there are few trials investigating antioxidant supplementation in female reproduction. However, before clinicians recommend antioxidants, randomized controlled trials with sufficient power are necessary to prove the efficacy of antioxidant supplementation in disorders of female reproduction. Serial measurement of oxidative stress biomarkers in longitudinal studies may help delineate the etiology of some of the diosorders in female reproduction such as preeclampsia.

Nitric Oxide Mediates Inhibitory Effect of Leptin on Insulin-Like Growth Factor I Augmentation of 17β-Estradiol Production in Human Granulosa Cells1

In the present study the authors investigated if the inhibitory effect of leptin in the ovary was mediated via nitric oxide (NO) using human granulosa cells (GCs). Human GCs were obtained from preovulatory follicles of women who underwent IVF. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated that human GCs expressed mRNA of leptin and mRNA of isoforms of leptin receptor, including one long form and two types of short forms. Exposure of human GCs to leptin at concentrations of 3-30 ng/ml for 60 min dose-dependently increased the fluorescence of 4,5-diaminofluorescein (DAF-2), an NO-sensitive dye. The effect of leptin on DAF-2 fluorescence was inhibited by pretreatment of human GCs with 100 microM nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase (NOS), indicating that the increase in DAF-2 fluorescence properly reflected the intracellular NO production. FSH (1 ng/ ml) and IGF-I (30 ng/ml) stimulated 17beta-estradiol (E2) production in human GCs, respectively. FSH plus IGF-I induced a further increase in E2 production. Leptin did not significantly alter basal or FSH-dependent E2 production, but it inhibited the effect of IGF-I on E2 production and the synergistic effect of IGF-I on FSH-stimulated E2 production. The inhibitory effect of leptin on IGF-I argumentation of E2 production was attenuated by pretreatment of human GCs with 100 microM L-NAME. In conclusion, leptin could induce NO production in human GCs. The inhibitory effect of leptin on IGF-I augmentation of E2 production in human GCs was attenuated by L-NAME, strongly suggesting that NO may mediate the action of leptin in human GCs.

Activation of soluble guanylyl cyclase inhibits estradiol production and cyclic AMP accumulation from cultured rat granulosa cells

OBJECTIVE

To demonstrate the expression of soluble guanylyl cyclase (sGC) alpha and beta subunits in rat granulosa cells and determine the effects sGC activation on levels of cyclic GMP (cGMP), E2, and cAMP.

DESIGN

Basic research study.

SETTING

University research laboratory.

ANIMAL(S)

Estrogen-treated immature Sprague-Dawley female rats from which primary cell culture of granulosa cells was obtained.

INTERVENTION(S)

Functionally immature rat granulosa cells were incubated for 48 hours with media alone, FSH, or FSH plus YC-1, a specific activator of sGC.

MAIN OUTCOME MEASURE(S)

Expression of sGC alpha and beta subunits was determined by immunoblot analysis. Media concentrations of E2, cAMP, and cGMP were measured by radioimmunoassays.

RESULT(S)

Immunoblot analysis of granulosa cells revealed the expression of sGC alpha and beta subunits. While cGMP accumulation was low in cells incubated with media alone or with FSH, cotreatment with FSH plus YC-1 increased cGMP levels approximately five-fold. Incubation of cells with FSH stimulated E2 production in a dose-dependent manner. However, cotreatment of cells with FSH plus YC-1 significantly decreased E2 concentrations at all doses of FSH tested. Similarly, while FSH increased cAMP accumulation from granulosa cells, cotreatment with YC-1 markedly inhibited FSH-stimulated cAMP levels.

CONCLUSION(S)

These findings demonstrate the expression of sGC subunits in rat granulosa cells and indicate that activation of sGC increases cGMP levels, which are associated with inhibition of FSH-stimulated E2 production and cAMP accumulation.

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.