Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and the related nitric oxide/cyclic GMP signaling pathway in the ovaries of neonatal and immature rats

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.

Hemoglobin: potential roles in the oocyte and early embryo†

Hemoglobin (Hb) is commonly known for its capacity to bind and transport oxygen and carbon dioxide in erythroid cells. However, it plays additional roles in cellular function and health due to its capacity to bind other gases including nitric oxide. Further, Hb acts as a potent antioxidant, quenching reactive oxygen species. Despite its potential roles in cellular function, the preponderance of Hb research remains focused on its role in oxygen regulation. There is increasing evidence that Hb expression is more ubiquitous than previously thought, with Hb and its variants found in a myriad of cell types ranging from macrophages to spermatozoa. The majority of nonerythroid cell types that express Hb are situated within hypoxic environments, suggesting Hb may play a role in hypoxia-inducible factor-regulated gene expression by controlling the level of oxygen available or as an adaptation to low oxygen providing a mechanism to store oxygen. Oocyte maturation and preimplantation embryo development occur within the low oxygen environments of the antral follicle and oviduct/uterus, respectively. Interestingly, Hb was recently found in human cumulus and granulosa cells and murine cumulus-oocyte complexes and preimplantation embryos. Here, we consolidate and analyze the research generated todate on Hb expression in nonerythroid cells with a particular focus on reproductive cell types. We outline future directions of this research to elucidate the role of Hb during oocyte maturation and preimplantation embryo development and finally, we explore the potential clinical applications and benefits of Hb supplementation during the in vitro culture of gametes and embryos.

Nitric Oxide Synthase Is Involved in Follicular Development via the PI3K/AKT/FoxO3a Pathway in Neonatal and Immature Rats

It is assumed that nitric oxide synthase and nitric oxide are involved in the regulation of female reproduction. This study aimed to assess the roles of nitric oxide synthase (NOS) in follicular development. The endothelial NOS (eNOS) inhibitor L-NAME, inducible NOS (iNOS) inhibitor S-Methylisothiourea (SMT) and NOS substrate L-arginine (L-Arg) were used in the NOS inhibition models in vivo. Neonatal female rats were treated with phosphate buffer saline (PBS, control), L-NAME (L-NG-Nitroarginine Methyl Ester, 40 mg/kg), SMT (S-Methylisothiourea, 10 mg/kg), L-NAME + SMT, or L-Arg (L-arginine, 50 mg/kg) via subcutaneous (SC) injection on a daily basis for 19 consecutive days, with the samples being collected on specific postnatal days (PD5, PD10, and PD19). The results indicated that the number of antral follicles, the activity of total-NOS, iNOS, neuronal NOS (nNOS), and eNOS, and the content of NO in the ovary were significantly (p < 0.05) increased in the L-Arg group at PD19, while those in L + S group were significantly (p < 0.05) decreased. Meanwhile, the ovarian expression in the L-Arg group in terms of p-AKT, p-FoxO3a, and LC3-II on PD19 were significantly (p < 0.05) upregulated, while the expressions of PTEN and cleaved Caspase-3 were (p < 0.05) downregulated as a result of NOS/NO generation, respectively. Therefore, the results suggest that NOS is possibly involved in the maturation of follicular development to puberty via the PI3K/ AKT/FoxO3a pathway, through follicular autophagia and apoptosis mechanisms.

Expression and Contribution of NLRP3 Inflammasome During the Follicular Development Induced by PMSG

Follicular development and following ovulation induced by luteinizing hormone (LH) surge are critical for ovarian functions, but the molecular mechanism regulating ovarian ovulation attracts more attention and remains mainly unknown. Recent researches on the nucleotide leukin rich polypeptide 3 (NLRP3) inflammasome shred light on it. Given pregnant mare serum gonadotropin (PMSG) can not only trigger the follicular development, but also induce the following ovulation, the present study therefore examined that expression and localization of NLRP3 inflammasome through immunohistochemistry and Western blotting during the follicular development induced by PMSG. The results showed expressions of NLRP3 and the adaptor protein apoptosis-associated speck-like protein (ASC) significantly increased in the outside of intrafollicular fluid, further analysis found that caspase-1 was activated and IL-1β production was also upregulated after 52 h-treatment of PMSG. Furthermore, a significant increase of ovulation-related genes, hypoxia inducible factor (HIF)-1α and endothelin (ET)-1, was found after 52 h-treatment of PMSG. To our knowledge, it is the first time to clearly indicated the activation of NLRP3 inflammasome may contribute to the ovulation of PMSG-treated ovaries, which will help to further clarify the ovulatory mechanism in mammals.

Expression of nitric oxide synthase (NOS) in Anabas testudineus ovary and participation of nitric oxide-cyclic GMP cascade in maintenance of meiotic arrest

Participation of cyclic nucleotide-mediated signaling in nitric oxide/soluble guanylate cyclase (NO/sGC) regulation of oocyte maturation (OM) in perch (Anabas testudineus) follicle-enclosed oocytes has been investigated. Congruent with sharp decline in follicular cyclic GMP (cGMP) level, nitric oxide synthase (NOS)-inhibitor (L-NAME) attenuates protein kinase A (PKA) phosphorylation but promotes p-ERK1/2 and p-p34Cdc2 (Thr-161) in maturing oocytes. Conversely, NO donor (SNP) prevents OM, potentially through elevated cGMP synthesis. Expression and localization of Nos2 and Nos3 immunoreactivity in perch ovary varied considerably at progressively higher stages of folliculogenesis. While sGC inhibitor (ODQ) alone could induce OM, 8-bromo-cGMP attenuates 17,20β-P-induced OM indicating functional significance of NO/sGC/cGMP in perch ovary. Interestingly, high NO/cGMP inhibition of OM shows positive relation with elevated cAMP level. MIS induced OM is more susceptible to the oocyte-specific phosphodiesterase (PDE) 3 than PDE4 inhibition. Collectively, high NO/cGMP attenuation of OM potentially involves PDE3 inhibition, cAMP accumulation and PKA activation.

Resveratrol Protects against Restraint Stress Effects on Stomach and Spleen in Adult Male Mice

The objectives were to investigate whether restraint stress (which is known as a mixture of psychologic and physical stress) exerts negative effects on the stomach and spleen, and whether the phenolic compound resveratrol (RES) exerts any protective roles. Fifty adult male mice were divided into five groups, with 10 mice per group as follows: control (C), restraint stress (RS), RS with vehicle (RS + V), RS with 2 mg/kg of resveratrol (RS + 2 mg RES), and RS with 20 mg/kg of resveratrol (RS + 20 mg RES). Mice were restrained in conical centrifuge tubes for 4 h daily to establish the RS model. RS + 2 mg RES, RS + 20 mg RES, and RS + V groups were given an oral dose of resveratrol or vehicle for 15 consecutive days, while the control group was not exposed to restraint stress. Herein, we showed that restraint stress decreased body weight and food and water consumption in stressed groups RS and RS + V compared to controls, while the groups treated with resveratrol showed improvements. Moreover, restraint stress caused acute damage to the morphology of gastric cells and reduced the quantitative distribution of parietal cells along with their decreased size and diameter, pointing to gastritis or ulcer. Furthermore, the antibody against the apoptosis-inducing factor (AIF) was highly attached in the RS groups. Splenic size, weight, and length were also greatly augmented in the stressed groups compared to the controls, while these phenomena were not observed in the RS + 2 mg RES group. Our findings proved significant ameliorating effects of resveratrol against restraint stress in adult male mice.

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.

Effects of aerobic exercise on the expressions and activities of nitric oxide synthases in the blood vessel endothelium in prediabetes mellitus

Previous studies by our group have indicated that exercise intervention can ameliorate endothelial dysfunction, which is an early pathophysiological change of prediabetes mellitus. The present study aimed to test the hypothesis that nitric oxide synthases (NOSs), which are expressed in blood vessel endothelium, contribute to the mitigation of vascular endothelium-dependent dysfunction by aerobic exercise in prediabetes mellitus. A prediabetic rat model was established by feeding the rats an additional high-energy diet, and was confirmed by testing blood glucose levels, the area-under-the-curve for the blood glucose tests (P<0.05) and the changes to the histological morphology of the thoracic aorta. Further examination identified that NOS expression changed significantly between the control and prediabetes groups, indicating endothelial dysfunction in the prediabetic rats. Following aerobic exercise, a significant increase in NOS, endothelial (eNOS) mRNA and protein expression (P<0.05), and a significant decrease in NOS, inducible (iNOS) mRNA and protein expression (P<0.05) was identified in the prediabetic rats compared with the control group. No significant change in nitric oxide synthase, brain expression was observed in the prediabetic rat group compared with the control group. Notably, there was also a significant increase and decrease in eNOS and iNOS activity, respectively, in the prediabetes group compared with the control group (P<0.05). Furthermore, nitric oxide (NO) concentration in the vascular endothelium was detected, which revealed a significant increase in NO concentration in the prediabetic rats following aerobic exercise compared with the control (P<0.05). The present study provided results that demonstrated that aerobic exercise ameliorated the vascular endothelium-dependent dysfunction through the NOS/NO signaling pathway, which is primarily regulated by NOS expression and activity, in prediabetes mellitus. The current study provided the theoretical basis for the use of exercise intervention to prevent diabetes mellitus during the early stage.

The production of nitric oxide in the coeliac ganglion modulates the effect of cholinergic neurotransmission on the rat ovary during the preovulatory period

The aim of the present work was to investigate whether the nitric oxide produced by the nitric oxide/nitric oxide synthase (NO/NOS) system present in the coeliac ganglion modulates the effects of cholinergic innervation on oxidative status, steroidogenesis and apoptotic mechanisms that take place in the rat ovary during the first proestrous. An ex vivo Coeliac Ganglion- Superior Ovarian Nerve- Ovary (CG-SON-O) system was used. Cholinergic stimulation of the CG was achieved by 10^-6 M Acetylcholine (Ach). Furthermore, 400 μM Aminoguanidine (AG) - an inhibitor of inducible-NOS was added in the CG compartment in absence and presence of Ach. It was found that Ach in the CG compartment promotes apoptosis in ovarian tissue, probably due to the oxidative stress generated. AG in the CG compartment decreases the release of NO and progesterone, and increases the release of estradiol from the ovary. The CG co-treatment with Ach and AG counteracts the effects of the ganglionic cholinergic agonist on ovarian oxidative stress, increases hormone production and decreases Fas mRNA expression. These results suggest that NO is an endogenous modulator of cholinergic neurotransmission in CG, with implication in ovarian steroidogenesis and the apoptotic mechanisms that take place in the ovary during the preovulatory period in rats.

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.

Thyroid hormones alter estrous cyclicity and antioxidative status in the ovaries of rats

To expand our understanding of the roles of thyroid hormones on female reproduction, we induced hypo- and hyper-T rat models to investigate the roles of thyroid hormones on estrous cyclicity, as well as the antioxidative status in the ovaries of rats. In the current study, our data show that hypothyroidism (hypo-T) and hyperthyroidism (hyper-T) led to significantly reduced body weights and ovarain weights and delayed vaginal opening day. For hyper-T, thyroxine (T4), tri-iodothyronine (T3), progesterone (P4) and follicle-stimulating hormone (FSH) were significantly increased, while estradiol (E2) and luteinizing hormone (LH) were significantly decreased. For hypo-T rats, serum levels of total T4 and T3, E2, P4, FSH and LH were significantly increased, while concentrations of E2 and LH were significantly decreased. For ovary morphology, the numbers of secondary and antral follicles were significantly decreased with more atretic antral follicles and less corpora lutea in both hyper- and hypo-T groups. Both hyper-T and hypo-T treatment significantly decreased the expressions of thyroid hormone receptor α1 in the ovary. Hypo-T significantly reduced nitric oxide (NO), total NO synthase (tNOS), inducible NOS and constitutive NOS activities, but hyper-T increased them. For antioxidative parameters, hypo-T and hyper-T treatment significantly increased malondialdehyde (MDA) contents. The activities of both glutathione peroxidase (GSH-Px) and catalase (CAT) significantly decreased in the hypo-T group but increased in the hyper-T group. Total superoxide dismutase (T-SOD) activity was significantly increased in the hyper-T group. In summary, thyroid hormones alter estrous cyclicity and antioxidative status in the ovary of the rat may act through the NOS signaling pathway.

Nitric Oxide-Mediated Regulation of GLUT by T3 and Follicle-Stimulating Hormone in Rat Granulosa Cells

Thyroid hormones are important for normal reproductive function. Although 3,5,3'-triiodothyronine (T3) enhances follicle-stimulating hormone (FSH)-induced preantral follicle growth and granulosa cells development in vitro, little is known about the molecular mechanisms regulating ovarian development via glucose. In this study, we investigated whether and how T3 combines with FSH to regulate glucose transporter protein (GLUT) expression and glucose uptake in granulosa cells. In this study, we present evidence that T3 and FSH cotreatment significantly increased GLUT-1/GLUT-4 expression, and translocation in cells, as well as glucose uptake. These changes were accompanied by upregulation of nitric oxide (NO) synthase (NOS)3 expression, total NOS and NOS3 activity, and NO content in granulosa cells. Furthermore, we found that activation of the mammalian target of rapamycin (mTOR) and phosphoinositide 3-kinase (PI3K)/Akt pathway is required for the regulation of GLUT expression, translocation, and glucose uptake by hormones. We also found that l-arginine upregulated GLUT-1/GLUT-4 expression and translocation, which were related to increased glucose uptake; however, these responses were significantly blocked by N(G)-nitro-l-arginine methylester. In addition, inhibiting NO production attenuated T3- and FSH-induced GLUT expression, translocation, and glucose uptake in granulosa cells. Our data demonstrate that T3 and FSH cotreatment potentiates cellular glucose uptake via GLUT upregulation and translocation, which are mediated through the activation of the mTOR/PI3K/Akt pathway. Meanwhile, NOS3/NO are also involved in this regulatory system. These findings suggest that GLUT is a mediator of T3- and FSH-induced follicular development.

Nitric oxide in follicle development and oocyte competence

Apart from its well-known role in regulating endothelial function, in mammals, nitric oxide (NO) is an important signaling molecule involved in many processes, regulating different biological functions. It has been demonstrated that NO plays a role in the physiology of the reproductive system, where it acts in controlling the activity of reproductive organs in both sexes. In the female of several animal species, experimental data suggest the presence of an intraovarian NO-generating system, which could be involved in the control of follicular development. The role of NO in regulating follicular atresia by apoptosis is still controversial, as a dual action depending mostly on its concentration has been documented. NO also displays positive effects on follicle development and selection related to angiogenic events and it could also play a modulatory role in steroidogenesis in ovarian cells. Both in monovulatory and poliovulatory species, the increase in PGE2production induced by NO via a stimulatory effect on COX-2 activity appears to be a common ovulatory mechanism. Considerable evidence also exists to support an involvement of the NO/NO synthase system in the control of meiotic maturation of cumulus–oocyte complexes.

Effects of thyroid hormones on the antioxidative status in the uterus of young adult rats

Thyroid hormones and oxidative stress play significant roles in the normal functioning of the female reproductive system. Nitric oxide (NO), a free radical synthesized by nitric oxide synthases (NOS), participates in the regulation of thyroid function and is also a good biomarker for assessment of the oxidative stress status. Therefore, the purpose of this study was to investigate effects of thyroid hormones on uterine antioxidative status in young adult rats. Thirty immature female Sprague-Dawley rats were randomly divided into three groups: control, hypothyroid (hypo-T) and hyperthyroid (hyper-T). The results showed the body weights decreased significantly in both the hypo-T and hyper-T groups and that uterine weights were decreased significantly in the hypo-T group. The serum concentrations of total triiodothyronine (T3) and thyroxine (T4), as well as estradiol (E2), were significantly decreased in the hypo-T group, but increased in the hyper-T group. The progesterone (P4) concentrations in the hypo- and hyperthyroid rats markedly decreased. Immunohistochemistry results provided evidence that thyroid hormone nuclear receptor α/β (TRα/β) and three NOS isoforms were located in different cell types of rat uteri. The NO content and total NOS and inducible NOS (iNOS) activities were markedly diminished in the hypo-T group but increased in the hyper-T group. Moreover, the activities of both glutathione peroxidase (GSH-Px) and catalase (CAT) exhibited significant decreases and increases in the hypo-T and hyper-T groups, respectively. The malondialdehyde (MDA) contents in both the hypo-T and hyper-T groups showed a significant increase. Total superoxide dismutase (T-SOD) activity in the hypo- and hyper-T rats markedly decreased. In conclusion, these results indicated that thyroid hormones have an important influence on the modulation of uterine antioxidative status.

Roles of SIRT1 in granulosa cell apoptosis during the process of follicular atresia in porcine ovary

Ovarian follicular atresia is characterized by granulosa cell apoptosis, however, the exact mechanism is still unclear. Sirtuin 1 (SIRT1) is a NAD(+)-dependent deacetylase, which is associated with apoptosis in several of cell types, but its exact role in ovarian granulosa cell apoptosis is not clearly defined. In present study, we identified the involvement of SIRT1 in the process of follicle degeneration, which is known as "follicular atresia", both from in vivo models and cell culture data. The results of immunohistochemistry showed that SIRT1 was widely detected in non-apoptotic granulosa cells of follicles, but significantly decreased during the process of granulosa cell apoptosis. Quantitative real-time PCR and Western blot analysis showed that the expression levels of SIRT1 mRNA and protein were increased (P<0.05) during follicular atresia. In order to provide more evidences elucidating the roles of SIRT1 during the process of follicular atresia, granulosa cells were cultured in vitro with resveratrol which acts as a potent activator of SIRT1. Results showed that resveratrol caused a dose-dependent increase in both SIRT1 mRNA and protein levels. Meanwhile, apoptotic rate of granulosa cell was increased (P<0.01) in a dose-dependent manner. Additionally, resveratrol significantly increased the expression levels of Caspase-3 (P<0.01) and Bax mRNA (P<0.01), while Bcl-2 mRNA level was significantly decreased (P<0.01). Thus, our results suggest that SIRT1 may play important roles in the regulation of granulosa cell apoptosis during follicular atresia in porcine ovary.

Expression of repulsive guidance molecule b (RGMb) in the uterus and ovary during the estrous cycle in rats

Repulsive guidance molecule b (RGMb; a.k.a. Dragon), initially identified in the embryonic dorsal root ganglion, is the first member of the RGM family shown to enhance bone morphogenetic protein (BMP) signaling by acting as a BMP co-receptor. BMP signaling has been demonstrated to play an important role in the reproductive organs. Our previous study found that RGMb was expressed in the reproductive axis, but whether RGMb expression in reproductive organs changes across the estrous cycle remains unknown. Here, we show in the rat that RGMb mRNA expression in the uterus was significantly higher during metesterus and diestrus than during proestrus and estrus. Western blotting indicated that RGMb protein was significantly lower during estrus compared with the other three stages. Immunohistochemistry revealed that RGMb protein was mainly localized to the uterine luminal and glandular epithelial cells of the endometrium. RGMb mRNA and protein in the ovary remained unchanged during the estrous cycle. RGMb protein was expressed in the oocytes of all follicles. Weak staining for RGMb protein was also found in corpora lutea. RGMb was not detected in granulosa cells and stromal cells. Taken together, RGMb expression in the uterus and ovary across the estrus cycle demonstrate that RGMb may be involved in the regulation of uterine function, follicular development as well as luteal activity.

Roles of thyroid hormones in follicular development in the ovary of neonatal and immature rats

Thyroid hormones (TH) play a critical role in ovarian follicular development, maturation and the maintenance of various endocrine functions. However, whether TH can affect ovarian follicular development in neonatal and immature rats remains unclear. Therefore, the aim of the present study was to elucidate the effect of TH on ovarian follicular development in neonatal and immature rats. Thirty female post-lactation mothers of Sprague-Dawley rat pups were randomly divided into three groups: control, hyperthyroid (hyper), and hypothyroid (hypo). On postnatal days (PND) 10 and 21, body weights, serum hormones, ovarian histologic changes, and immunohistochemistry of thyroid hormone receptor alpha 1 (TRα1) and nitric oxide synthase types (NOS), and NOS activities, were determined. The data showed that body weights significantly decreased in both hyper and hypo groups compared with the control group (P < 0.05). In addition, the hyper group had increased serum concentrations of T3, T4, and E2; whereas the hypo group manifested reduced serum concentrations of T3, T4, and E2 on PND 10 and 21. The hyper and hypo groups showed significantly reduced total number of primordial, primary and secondary follicles on PND 10 and 21 compared with the control group (P < 0.05). Similarly, antral follicle numbers in the hyper and hypo groups were significantly decreased on PND 21 compared with the control group (P < 0.05). Immunostaining indicated that TRα1 and NOS were expressed in ovarian surface epithelium and oocytes of growing and antral follicles, with strong staining of the granulosa and theca cells of follicles. NOS activities were significantly augmented in the hyper, but diminished in the hypo groups on PND 10 and 21. In summary, our findings suggest that TH play important roles in ovarian functions and in the regulation of NOS activity. Our results also indicate that a relationship exists between the TH and NO signaling pathways during the process of ovarian follicular development in neonatal and immature rats.

Reproductive toxicity in acrylamide-treated female mice

We investigated the reproductive toxicity of acrylamide in female mice. The results from immunohistochemistry provided evidence that nitric oxide synthase (NOS) signaling was involved in the process of follicular development and atresia. Oral administration of acrylamide to female mice led to significantly reduced body weights, organ weights and the number of corpora lutea (P<0.05). Serum progesterone concentrations were significantly reduced (P<0.05) concomitant with the increasing doses of acrylamide; however, 17β-estradiol (E2) concentrations were unchanged with treatment. Measurement of NOS activities indicated that total NOS (TNOS), iNOS and eNOS activities were significantly increased (P<0.05) with increasing doses of acrylamide. The results from in vitro study indicated that acrylamide reduced the viability of mouse granulosa cells in a dose-dependent manner. In summary, acrylamide affected bodily growth and development, as well as reproductive organs, the number of corpora lutea and progesterone production in female mice, possibly acting through the NOS signaling pathway.

Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and soluble guanylyl cyclase α and β subunits in postnatal porcine uteri

The aim of the present study was to investigate the cellular expression and immunolocalization of nitric oxide synthase (NOS) isoforms and soluble guanylyl cyclase (sGC) subunits in postnatal porcine uteri. Immunohistochemical experiments showed that three isoforms of NOS were mainly localized in the uterine luminal and glandular epithelium and myometrium, and the intensity of immunostaining for iNOS and eNOS was increased gradually with temporal development of the postnatal uterus. In addition, sGC subunits, sGCα1 and β, were present in the uterine luminal and glandular epithelium, myometrium and stromal cells. The uterine NOS activity data showed that the total NOS and iNOS activities were significantly increased at postnatal days 21 and 35. Although constitutive NOS activity was increased at postnatal day 21, it decreased subsequently at postnatal day 35. Immunoblot analysis revealed that iNOS protein expression was significantly increased at postnatal days 21 and 35. Furthermore, sGCα1 protein expression was not significantly changed throughout days 7 to 35. Collectively, our findings suggest that NO/cGMP signaling is involved in the process of postnatal porcine uterine development.

Cleavage of poly (ADP-ribose) polymerase-1 is involved in the process of porcine ovarian follicular atresia

Ovarian follicle atresia is a common phenomenon in vertebrate ovaries and this process is characterized by follicular wall degeneration. The molecular mechanism underlying follicle atresia is apoptotic granulusa cell death; however, the exact signaling pathway is still unclear. PARP-1, the founding member of the poly (ADP-ribose) polymerase (PARP) family, plays an important role in a large variety of physiological processes. Although its cleavage has recently been implicated in a variety of physiological and pathological processes, its role in the process of follicular atresia is not yet completely defined. We identified the cleavage of PARP-1 involved in the process of follicle degeneration, which is known as "follicular atresia", both from in vivo models and cell culture data. The results from immunohistochemistry (IHC) showed that cleaved PARP-1 was mainly located in apoptotic granulosa cells (GCs); and the expression of PARP-1 and caspase-3 were decreased in apoptotic granulosa cells (GCs). The results from western blotting showed that PARP-1 expression was significantly decreased in atretic follicles compared with healthy (H) follicles, and the cleavage of caspase-3 (17kDa) significantly increased in atretic follicles. Along with the cleavage of caspase-3, the expression of cleaved PARP-1 (24kDa) product was significantly increased, which confirmed caspase-3 activation. Serum starvation led to a reduction in PARP-1 and an increase in cleaved PARP-1 (24kDa) and caspase-3 (17kDa), suggesting that caspase-3 was activated under the stress of withdrawal of growth factors, in accordance with the in vivo study. In the present study, the concentrations of estradiol (E2) and progesterone (P4) as well as the P4/E2 (P/E) ratio were combined with morphological features to determine follicular classification. In summary, the present study demonstrated that cleavage of PARP-1 by caspase-3 was involved in the process of granulosa cell apoptosis. PARP-1 may through its cleavage act as a critical regulator in the process of porcine follicular atresia. Our results identified that cleavage of PARP-1 by activated (cleaved) caspase-3 may serve a key role in controlling follicular atresia through granulosa cell degeneration. These findings should prove helpful in understanding the regulatory mechanisms controlling follicular development and atresia.

Different effects of L-arginine on morphine tolerance in sham and ovariectomized female mice

OBJECTIVE

The roles of gonadal hormones and nitric oxide (NO) on the analgesic effects of morphine, tolerance to morphine, and their interactions have been widely investigated. In the present study, the effect of L-arginine (an NO precursor) on morphine tolerance in sham and ovariectomized (OVX) female mice was investigated.

METHODS

Forty mice were divided into sham and OVX groups. On the first day, a hot plate test ((55±0.2) °C; cut-off 30 s) was carried out as a base record 15 min before injection of morphine (10 mg/kg, subcutaneously (s.c.)) and was repeated every 15 min after injection. The sham group was then divided into two subgroups: sham-tolerance-L-arginine (Sham-Tol-LA) and sham-tolerance-saline (Sham-Tol-Sal) which received either L-arginine 50 mg/kg (intraperitoneally (i.p.)) or saline 10 ml/kg (i.p.), respectively, three times in a day for three consecutive days. Morphine tolerance was induced in animals by injecting 30 mg/kg morphine (s.c.) three times/day for three days. This treatment was also used for OVX subgroups. On the fifth day, the hot plate test was repeated. The analgesic effect of morphine was calculated as the maximal percent effect (MPE). The results were compared using repeated measure analysis of variance (ANOVA).

RESULTS

There was no significant difference in MPE between the OVX and sham groups. The MPEs in both the Sham-Tol-Sal and OVX-Tol-Sal groups were lower than those in both the sham and OVX groups (P<0.01). The MPE in the OVX-Tol-Sal group was greater than that in the Sham-Tol-Sal group (P<0.01). The MPE in the Sham-Tol-LA group was higher than that in the Sham-Tol-Sal group (P<0.01). However, there was no significant difference between the Sham-Tol-LA and sham groups or between the OVX-Tol-LA and OVX-Tol-Sal groups.

CONCLUSIONS

The results of the present study showed that repeated administration of morphine causes tolerance to the analgesic effect of morphine. L-arginine could prevent tolerance to morphine but its effect was different in the presence of ovarian hormones.

Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and soluble guanylyl cyclase α1 and β1 subunits in the ovary of fetal, neonatal and immature pigs

The present study is designed to investigate the cellular expression and immunolocalization of three different nitric oxide synthase (NOS) isoforms and soluble guanylyl cyclase (sGC) subunits in the porcine ovary. Our results showed that in the fetal and neonatal pigs, all three isoforms of NOS were mainly localized in the oocyte and showed the expression of gradual increase in the granulosa cell and theca cell with the growing follicle. In addition, subunits of the sGC, sGC α1 and β1 were mainly expressed in the granulosa cell in precious studies. The bioactivity of total NOS, eNOS, iNOS and nNOS was detected in the ovary and were higher at prenatal stages compared to postnatal stages. However, the activities of nNOS were no different between prenatal stages and postnatal stages. Taken together, our findings suggested that the NOS/sGC pathway may be involved in the follicular formation and development in the porcine ovary.

Effects of exogenous 17β-estradiol on follicular development in the neonatal and immature mouse in vivo

Purpose

The study was aimed to examine the effects of exogenous 17β-estradiol (E₂) on oocyte nest breakdown and follicular growth in the ovary of neonatal and immature mice.

Methods

The effect of E₂ on primordial follicle formation and differentiation were examined by treating neonatal mice with E₂ in mineral oil at a dose of 10 mg/kg by sc injection each day from postnatal days 1 (PND1) to 10 (PND10). This investigation was conducted by using histological observation and immunohistochemical staining of proliferating cell nuclear antigen (PCNA); the numbers of follicles at each stage were examined to assess the follicular development.

Results

The results indicated that such dose of E₂ inhibited oocyte nest breakdown from PND1 to PND10 significantly and enhanced the oocyte staining intensity of PCNA in the ovary by PND3, 5 and 10. PCNA staining was mainly detected on growing follicles (stages later than primary follicle). Our results also revealed that E₂ decreased the size of the reproductive tract at PD10.

Conclusions

This dose of E₂ treatment inhibits oocyte nest breakdown and primordial follicle assembly, and causes follicle losses after PND5. Effects of exogenous E₂ on follicular development in the neonatal and immature mouse may through a PCNA-dependent pathway.

Age-dependent expression of forkhead box O proteins in the duodenum of rats

The O subfamily of forkhead box (FoxO) proteins is the downstream effector of the insulin-like growth factor-1/phosphoinositide 3-kinase/protein kinase B (IGF-1/PI3K/PKB) signal pathway. The objective of the present study was to examine the expressions of three members of FoxO proteins, FoxO1, FoxO3a, and FoxO4 in the duodenum of Sprague-Dawley rats at different ages. The result demonstrated that the expression of FoxO4 in rat duodenum showed an age-dependent manner. At Day 21, there were no detectable localization and expression of FoxO4 in the duodenum, while, at Months 2 and 6, localization and expression of FoxO4 were distinct. In addition, FoxO4 staining was primarily concentrated in the cell nuclei of the lamina propria around the intestinal gland of the duodenum in 2-month-old rats, but was not detectable in the same area in 6-month-old rats. Our results showed also that although FoxO3a existed in the cytoplasm of the lamina propria at a low level at the 2- and 6-month marks, it was still not detectable at Day 21. Besides, FoxO1 was not detectable in all parts and stages. Taken together, our findings suggested that the cell-specific and age-dependent expressional patterns of FoxO4 and FoxO3a proteins in the duodenum play some roles in the development and growth performance of the rat duodenum.