Intracellular cAMP and calcium signaling by serotonin in mouse cumulus-oocyte complexes

Serotonin Signaling in Mouse Preimplantation Development: Insights from Transcriptomic and Structural-Functional Analyses

Serotonin (5-HT), a versatile signaling molecule, plays a variety of roles in both neurotransmission and tissue regulation. The influence of serotonin on early development was first studied in marine invertebrate embryos and has since been documented in a variety of vertebrate species, including mammals. The present study investigates the expression and functional activity of serotonin components in mouse embryos, focusing on key receptors and transporters. Transcriptomic analyses revealed that mRNA transcripts related to serotonin show marked expression during the oogenesis and preimplantation stages. The results of the immunohistochemical studies show the presence of serotonin, the vesicular monoamine transporter VMAT2, and several membrane receptors (5-HT1B, 5-HT1D, 5-HT2B, 5-HT7) in the early stages of development. A functional analysis performed with the VMAT inhibitor reserpine revealed the crucial role of vesicular transport in the maintenance of serotonin signaling. The findings presented here support the hypothesis that serotonin plays a significant role in oocyte maturation and embryonic development, as well as in interblastomere interactions.

Effect of Serotonin (5-Hydroxytryptamine) on Follicular Development in Porcine

5-Hydroxytryptamine (5-HT) is an inhibitory neurotransmitter widely distributed in mammalian tissues, exerting its effects through binding to various receptors. It plays a crucial role in the proliferation of granulosa cells (GCs) and the development of follicles in female animals, however, its effect on porcine follicle development is not clear. The aim of this study is to investigate the expression of 5-HT and its receptors in various parts of the pig ovary, as well as the effect of 5-HT on porcine follicular development by using ELISA, quantitative real-time PCR (qPCR) and EdU assays. Firstly, we examined the levels of 5-HT and its receptors in porcine ovaries, follicles, and GCs. The findings revealed that the expression of different 5-HT receptors varied among follicles of different sizes. To investigate the relationship between 5-HT and its receptors, we exposed the GCs to 5-HT and found a decrease in 5-HT receptor expression compared to the control group. Subsequently, the treatment of GCs with 0.5 μM, 5 μM, and 50 μM 5-HT showed an increase in the expression of cell cycle-related genes, and EdU results indicated cell proliferation after the 0.5 μM 5-HT treatment. Additionally, the expression of genes involved in E2 synthesis was examined after the treatment of granulosa cells with 0.5 μM 5-HT. The results showed that CYP19A1 and HSP17β1 expression was decreased. These results suggest that 5-HT might affect the development of porcine follicle by promoting the proliferation of GCs and inhibiting the synthesis of estrogen. This provides a new finding for exploring the effect of 5-HT on follicular development, and lays a foundation for further research on the mechanism of 5-HT in follicles.

Minerals and the Menstrual Cycle: Impacts on Ovulation and Endometrial Health

The role of minerals in female fertility, particularly in relation to the menstrual cycle, presents a complex area of study that underscores the interplay between nutrition and reproductive health. This narrative review aims to elucidate the impacts of minerals on key aspects of the reproductive system: hormonal regulation, ovarian function and ovulation, endometrial health, and oxidative stress. Despite the attention given to specific micronutrients in relation to reproductive disorders, there is a noticeable absence of a comprehensive review focusing on the impact of minerals throughout the menstrual cycle on female fertility. This narrative review aims to address this gap by examining the influence of minerals on reproductive health. Each mineral's contribution is explored in detail to provide a clearer picture of its importance in supporting female fertility. This comprehensive analysis not only enhances our knowledge of reproductive health but also offers clinicians valuable insights into potential therapeutic strategies and the recommended intake of minerals to promote female reproductive well-being, considering the menstrual cycle. This review stands as the first to offer such a detailed examination of minerals in the context of the menstrual cycle, aiming to elevate the understanding of their critical role in female fertility and reproductive health.

The differential sensitivity of the hypothalamic-hypophysial-ovarian axis to 5-hydroxytryptophan alters the secretion of estradiol

Serotonin [5-hydroxytryptamine (5-HT)] modulates ovarian function. The precursor of 5-HT, 5-hydroxytryptophan (5-HTP), has been used to treat depression. However, the effects of 5-HTP on ovarian and reproductive physiology remain unknown. In this research, we analysed the impact of 5-HTP on the monoaminergic system and its interactions with the reproductive axis and ovarian estradiol secretion when administered by distinct routes. Female rats 30 days of age were injected with 5-HTP i.p. (100 mg/kg), into the ovarian bursa (1.5 µg/40 µL) or into the median raphe nucleus (20 µg/2.5 µL) and were killed 60 or 120 min after injection. As controls, we used rats of the same age injected with vehicle (0.9% NaCl). Monoamine, gonadotrophin and steroid ovarian hormone concentrations were measured. The injection of 5-HTP either i.p. or directly into the ovarian bursa increased the concentrations of 5-HT and the metabolite 5-hydroxyindole-3-acetic acid in the ovary. For both routes of administration, the serum concentration of estradiol increased. After i.p. injection of 5-HTP, the concentrations of luteinizing hormone were decreased and follicle-stimulating hormone increased after 120 min. Micro-injection of 5-HTP into the median raphe nucleus increased the concentrations of 5-HT in the anterior hypothalamus and dopamine in the medial hypothalamus after 120 min. Our results suggest that the administration of 5-HTP either i.p. or directly into the ovarian bursa enhances ovarian estradiol secretion.

The molecular regulatory mechanisms of meiotic arrest and resumption in Oocyte development and maturation

In human female primordial germ cells, the transition from mitosis to meiosis begins from the fetal stage. In germ cells, meiosis is arrested at the diplotene stage of prophase in meiosis I (MI) after synapsis and recombination of homologous chromosomes, which cannot be segregated. Within the follicle, the maintenance of oocyte meiotic arrest is primarily attributed to high cytoplasmic concentrations of cyclic adenosine monophosphate (cAMP). Depending on the specific species, oocytes can remain arrested for extended periods of time, ranging from months to even years. During estrus phase in animals or the menstrual cycle in humans, the resumption of meiosis occurs in certain oocytes due to a surge of luteinizing hormone (LH) levels. Any factor interfering with this process may lead to impaired oocyte maturation, which in turn affects female reproductive function. Nevertheless, the precise molecular mechanisms underlying this phenomenon has not been systematically summarized yet. To provide a comprehensive understanding of the recently uncovered regulatory network involved in oocyte development and maturation, the progress of the cellular and molecular mechanisms of oocyte nuclear maturation including meiosis arrest and meiosis resumption is summarized. Additionally, the advancements in understanding the molecular cytoplasmic events occurring in oocytes, such as maternal mRNA degradation, posttranslational regulation, and organelle distribution associated with the quality of oocyte maturation, are reviewed. Therefore, understanding the pathways regulating oocyte meiotic arrest and resumption will provide detailed insight into female reproductive system and provide a theoretical basis for further research and potential approaches for novel disease treatments.

The Serotonergic System and Bone Metabolism During Pregnancy and Lactation and the Implications of SSRI Use on the Maternal-Offspring Dyad

Lactation is a physiological adaptation of the class Mammalia and is a product of over 200 million years of evolution. During lactation, the mammary gland orchestrates bone metabolism via serotonin signaling in order to provide sufficient calcium for the offspring in milk. The role of serotonin in bone remodeling was first discovered over two decades ago, and the interplay between serotonin, lactation, and bone metabolism has been explored in the years following. It is estimated that postpartum depression affects 10-15% of the population, and selective serotonin reuptake inhibitors (SSRI) are often used as the first-line treatment. Studies conducted in humans, nonhuman primates, sheep, and rodents have provided evidence that there are consequences on both parent and offspring when serotonin signaling is disrupted during the peripartal period; however, the long-term consequences of disruption of serotonin signaling via SSRIs during the peripartal period on the maternal and offspring skeleton are not fully known. This review will focus on the relationship between the mammary gland, serotonin, and bone remodeling during the peripartal period and the skeletal consequences of the dysregulation of the serotonergic system in both human and animal studies.

Tryptophan Hydroxylase-2-Mediated Serotonin Biosynthesis Suppresses Cell Reprogramming into Pluripotent State

The monoamine neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has important functions both in the neural system and during embryonic development in mammals. In this study, we set out to investigate whether and how endogenous serotonin affects reprogramming to pluripotency. As serotonin is synthesized from tryptophan by the rate limiting enzymes tryptophan hydroxylase-1 and -2 (TPH1 and TPH2), we have assessed the reprogramming of TPH1- and/or TPH2-deficient mouse embryonic fibroblasts (MEFs) to induced pluripotent stem cells (iPSCs). The reprogramming of the double mutant MEFs showed a dramatic increase in the efficiency of iPSC generation. In contrast, ectopic expression of TPH2 alone or in conjunction with TPH1 reverted the rate of reprogramming of the double mutant MEFs to the wild-type level and besides, TPH2 overexpression significantly suppressed reprogramming of wild-type MEFs. Our data thus suggest a negative role of serotonin biosynthesis in the reprogramming of somatic cells to a pluripotent state.

Recent advances in understanding adverse effects associated with drugs targeting the serotonin receptor, 5-HT GPCR

It has been acknowledged that more women suffer from adverse effects of drugs than men globally. A group of drugs targeting serotonin [5-hydroxytryptamine] (5-HT) binding G-protein-coupled receptors (GPCRs) have been reported to preferentially affect women more than men, causing adverse effects such as breast cancer and infertility. 5-HT GPCR-targeted drugs in the central nervous system (CNS) manage psychiatric conditions, such as depression or bipolar and in the peripheral nervous system (PNS) treat migraines. Physiological characteristics such as specific types of hormones, higher body fat density and smaller body mass in women result in disparities in pharmacodynamics of drugs, thus explaining sex-related differences in the observed adverse effects. In this review, we discuss the side effects of drugs targeting 5-HT GPCRs based on serotonin's roles in the CNS and PNS. We have systematically reviewed adverse effects of drugs targeting 5-HT GPCR using information from the Food and Drug Administration and European Medicines Agency. Further information on drug side effects and receptor targets was acquired from the SIDER and DrugBank databases, respectively. These drugs bind to 5-HT GPCRs in the CNS, namely the brain, and PNS such as breasts, ovaries and testes, potentially causing side effects within these areas. Oestrogen affects both the biosynthesis of 5-HT and the densities of 5-HT GPCRs in given tissues and cells. 5-HT GPCR-targeting drugs perturb this process. This is likely a reason why women are experiencing more adverse effects than men due to their periodic increase and the relatively high concentrations of oestrogen in women and, thus a greater incidence of the oestrogen-mediated 5-HT system interference. In addition, women have a lower concentration of serotonin relative to men and also have a relatively faster rate of serotonin metabolism which might be contributing to the former. We discuss potential approaches that could mitigate at least some of the adverse effects experienced by women taking the 5-HT GPCR-targeting drugs.

The Role of L-Arginine-NO System in Female Reproduction: A Narrative Review

Accumulating evidence are available on the involvement of l-arginine-nitric oxide (NO) system in complex biological processes and numerous clinical conditions. Particular attention was made to reveal the association of l-arginine and methylarginines to outcome measures of women undergoing in vitro fertilization (IVF). This review attempts to summarize the expression and function of the essential elements of this system with particular reference to the different stages of female reproduction. A literature search was performed on the PubMed and Google Scholar systems. Publications were selected for evaluation according to the results presented in the Abstract. The regulatory role of NO during the period of folliculogenesis, oocyte maturation, fertilization, embryogenesis, implantation, placentation, pregnancy, and delivery was surveyed. The major aspects of cellular l-arginine uptake via cationic amino acid transporters (CATs), arginine catabolism by nitric oxide synthases (NOSs) to NO and l-citrulline and by arginase to ornithine, and polyamines are presented. The importance of NOS inhibition by methylated arginines and the redox-sensitive elements of the process of NO generation are also shown. The l-arginine-NO system plays a crucial role in all stages of female reproduction. Insufficiently low or excessively high rates of NO generation may have adverse influences on IVF outcome.

Integrated analysis of the expression profiles of the lncRNA-miRNA-mRNA ceRNA network in granulosa and cumulus cells from yak ovaries

Background

Growing oocytes acquire the ability to mature through two-way communication between gametes and surrounding somatic cumulus cells (CCs). Granulosa cells (GCs) support oocyte growth, regulate meiosis progression, and modulate global oocyte transcription activity. However, the proliferation and differentiation of the yak ovary in GCs and CCs remain unclear. To characterize the important roles of long non-coding RNA, (lncRNA), microRNA (miRNA), and messenger RNA (mRNA), whole-transcriptome analysis was performed. Real-time quantitative fluorescence PCR was performed to verify the selected RNA sequences.

Results

Important gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways related to differentiation and oocyte development were identified for the target genes of differentially expressed lncRNAs, miRNAs, and mRNAs. In total,6223 mRNAs (2197 upregulated, 4026 downregulated), 643 lncRNAs (204 upregulated, 479 downregulated), and 559 miRNAs (311 upregulated, 248 downregulated) were significantly altered between the two groups. Target genes involved in cell adhesion, cell differentiation, regulation of developmental processes, cell proliferation, embryo development, signal transduction, apoptosis, and aromatic compound biosynthetic processes were significantly enriched. These RNAs were involved in ECM-receptor interaction, MAPK signaling, Hippo signaling, PI3K-Akt signaling, cell cycle, cell adhesion, leukocyte trans-endothelial migration, and actin cytoskeleton regulation.

Conclusions

A comprehensive analysis of the co-expression network of competing endogenous RNAs (ceRNAs) will facilitate the understanding of the process of granulosa cell proliferation and differentiation and offer a theoretical basis for the development of oocytes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08848-3.

Maternal Prepregnancy 5-Hydroxytryptamine Exposure Affects the Early Development of the Fetus

In recent decades, the increasing incidence of depression has contributed to an increase in the use of serotonergic drugs, such as antidepressants, which predisposes humans to serotonin syndrome. Serotonin syndrome is caused by elevated serotonin levels in the central and peripheral nervous systems. It has been well documented that the development of offspring can be affected by maternal exposure to environmental challenges, such as stress, diseases, or an unhealthy diet during pregnancy. Serotonin, also called 5-hydroxytryptamine (5-HT), is widely expressed in the female reproductive system and plays an important role in the development of follicles and embryos. However, whether the suffering of the mother from serotonin syndrome before pregnancy affects fetal development is still uncertain. In the present study, to explore the effect of maternal prepregnancy 5-HT exposure on the fetus, intraperitoneal injection of 5-HT was used to change maternal prepregnancy 5-HT levels. It was found that maternal prepregnancy 5-HT exposure significantly reduced the body weight and liver weight and the levels of estrogen and progesterone in female mice. Although there was no significant difference in the cleavage rate and blastocyst rate between the 5-HT and control groups, maternal prepregnancy 5-HT exposure increased the percentage of embryo resorption, decreased placental weight, and led to placental inflammation at E13.5. Notably, 5-HT exposure caused weight loss in the offspring at 2 weeks. These results suggested that maternal prepregnancy 5-HT exposure could affect the development of the offspring, which was partly caused by reduced hormonal secretion and placental inflammation.

Transcriptome profile of goat folliculogenesis reveals the interaction of oocyte and granulosa cell in correlation with different fertility population

To understand the molecular and genetic mechanisms related to the litter size in one species of two different populations (high litter size and low litter size), we performed RNA-seq for the oocytes and granulosa cells (GCs) at different developmental stages of follicle, and identified the interaction of genes from both sides of follicle (oocyte and GCs) and the ligand-receptor pairs from these two sides. Our data were very comprehensive to uncover the difference between these two populations regarding the folliculogenesis. First, we identified a set of potential genes in oocyte and GCs as the marker genes which can be used to determine the goat fertility capability and ovarian reserve ability. The data showed that GRHPR, GPR84, CYB5A and ERAL1 were highly expressed in oocyte while JUNB, SCN2A, MEGE8, ZEB2, EGR1and PRRC2A were highly expressed in GCs. We found more functional genes were expressed in oocytes and GCs in high fertility group (HL) than that in low fertility group (LL). We uncovered that ligand-receptor pairs in Notch signaling pathway and transforming growth factor-β (TGF-β) superfamily pathways played important roles in goat folliculogenesis for the different fertility population. Moreover, we discovered that the correlations of the gene expression in oocytes and GCs at different stages in the two populations HL and LL were different, too. All the data reflected the gene expression landscape in oocytes and GCs which was correlated well with the fertility capability.

Differential localization of serotoninergic system elements in human amniotic epithelial cells†

Serotonin or 5-hydroxytryptamine (5-HT) is a biogenic amine involved in regulating several functions, including development. However, its impact on human embryo development has been poorly studied. The present work investigated the expression and distribution of the main components of the serotoninergic system in human amniotic tissue and human amniotic epithelial cells (hAEC) in vitro, as an alternative model of early human embryo development. Amniotic membranes from full-term healthy pregnancies were used. Human amnion tissue or hAEC isolated from the amnion was processed for reverse transcription-polymerase chain reaction and immunofluorescence analyses of the main components of the serotoninergic system. We found the expression of tryptophan hydroxylase type 1 (TPH1), type 2 (TPH2), serotonin transporter (SERT), monoamine oxidase-A (MAOA), as well as HTR1D and HTR7 receptors at mRNA level in amnion tissue as well in hAEC. Interestingly, we found the presence of 5-HT in the nucleus of the cells in amnion tissue, whereas it was located in the cytoplasm of isolated hAEC. We detected TPH1, TPH2, and HTR1D receptor in both the nucleus and cytoplasm. SERT, MAOA, and HTR7 receptor were only observed in the cytoplasm. The results presented herein show, for the first time, the presence of the serotoninergic system in human amnion in vivo and in vitro.

Effects of miR-143 and its target receptor 5-HT2B on agonistic behavior in the Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab (Eriocheir sinensis) as a commercially important species is widely cultured in China. However, E. sinensis is prone to agonistic behavior, which causes physical damage and wastes energy resources, negatively impacting their growth and survival. Therefore, understanding the regulatory mechanisms that underlie the switching of such behavior is essential for ensuring the efficient and cost-effective aquaculture of E. sinensis. The 5-HT2B receptor is a key downstream target of serotonin (5-HT), which is involved in regulating animal behavior. In this study, the full-length sequence of 5-HT2B gene was cloned. The total length of the 5-HT2B gene was found to be 3127 bp with a 236 bp 5′-UTR (untranslated region), a 779 bp 3′-UTR, and a 2112 bp open reading frame encoding 703 amino acids. Phylogenetic tree analysis revealed that the 5-HT2B amino acid sequence of E. sinensis is highly conserved with that of Cancer borealis. Using in vitro co-culture and luciferase assays, the miR-143 targets the 5-HT2B 3′-UTR and inhibits 5-HT2B expression was confirmed. Furthermore, RT-qPCR and Western blotting analyses revealed that the miR-143 mimic significantly inhibits 5-HT2B mRNA and protein expression. However, injection of miR-143 did not decrease agonistic behavior, indicating that 5-HT2B is not involved in the regulation of such behavior in E. sinensis.

Role of serotonin in vertebrate embryo development

Since its discovery in 1937, serotonin (5-HT) has become one of the most studied biogenic amines due to its predominant role in regulating several physiological processes such as mood, sleep, and food intake. This amine and the main components of the serotoninergic system are in almost all cells of the body. The presence of 5-HT and the serotoninergic system has been observed in oocytes and in different embryo development stages of fish, amphibians, birds, and mammals. In several classes of vertebrates, the change in the concentration of 5-HT or the alteration of the serotoninergic system, interfere with early embryo development. These data suggest that 5-HT participates in embryo development of vertebrates.

Expression pattern of olfactory receptor genes in human cumulus cells as an indicator for competent oocyte selection

Odorant or olfactory receptors are mainly localized in the olfactory epithelium for the perception of different odors. Interestingly, many ectopic olfactory receptors with low expression levels have recently been found in nonolfactory tissues to involve in local functions. Therefore, we investigated the probable role of the olfactory signaling pathway in the surrounding microenvironment of oocyte. This study included 22 women in intracytoplasmic sperm injection cycle. The expression of olfactory target molecules in cumulus cells surrounding the growing and mature oocytes was evaluated by Western blotting and real-time polymerase chain reaction. Additionally, integrated bioinformatics analyses were carried out and 6 ectopic olfactory receptors were selected for further evaluation. The initiation of olfactory transduction cascade in cumulus cells of competent oocytes was confirmed by analyzing the expression of adenylyl cyclase type 3 and olfactory market protein. Moreover, the expression pattern of the selected olfactory receptors was evaluated and OR10H2 was selected due to a high level of expression in mature fertile oocytes. We suggested that OR10H2 could be considered as a reliable biomarker for oocyte selection in assisted reproduction technique programs. However, further studies are required to elucidate the role of olfactory transduction cascade in embryo quality and implantation.

Effects of perinatal factors on sirtuin 3, 8-hydroxy-2'- deoxyguanosine, brain-derived neurotrophic factor and serotonin in cord blood and early breast milk: an observational study

BACKGROUND

The profile of sirtuin 3 (SIRT3), 8-hydroxy-2'-deoxyguanosine (8-OHdG), brain-derived neurotrophic factor (BDNF) and serotonin (5-HT) in cord blood and in early breast milk was studied and it was related to perinatal factors. 5-HT and BDNF signalling systems have been claimed to play a critical role in intrauterine development, postnatal adaptation and lactation. Since prematurity and Caesarean birth are frequently associated with inflammation and related oxidative stress, an attempt was made to reveal the adaptive changes of the protective SIRT3 and the complex interplay among these bioactive components in cord blood and early breast milk.

METHODS

Three groups each consisting of 30 mothers were included in the study: mothers who underwent spontaneous vaginal birth at term (group I), Caesarean section at term (group II) and preterm birth (group III). Venous cord blood and early breast milk samples were collected for measuring the biomarkers. SIRT3, 8-OHdG, BDNF and 5-HT levels were determined by using commercially available ELISA kits.

RESULTS

It was demonstrated that cord blood levels of SIRT3, BDNF and 5-HT were markedly reduced whereas those of 8-OHdG were significantly elevated after preterm birth when compared with birth at term. The Caesarean section was associated with a moderate decrease in BDNF and 5-HT, however, both SIRT3 and 8-OHdG remained unaffected. Breast milk levels of all biomarkers studied proved to be independent of their corresponding cord blood concentrations. In response to preterm birth breast milk SIRT3, 8-OHdG and 5-HT increased significantly, while a drastic fall occurred in BDNF. A significant positive relationship was found of 5-HT with SIRT3 and 8-OHdG irrespective of the gestational age and the mode of delivery.

CONCLUSIONS

It is suggested that the selected biomarkers in the breast milk mostly derive from local production by the mammary glands and 5-HT may have an essential role in the control of this process.

Human Cumulus Cells in Long-Term In Vitro Culture Reflect Differential Expression Profile of Genes Responsible for Planned Cell Death and Aging-A Study of New Molecular Markers

In the ovarian follicle, maturation of the oocyte increases in the presence of somatic cells called cumulus cells (CCs). These cells form a direct barrier between the oocyte and external environment. Thanks to bidirectional communication, they have a direct impact on the oocyte, its quality and development potential. Understanding the genetic profile of CCs appears to be important in elucidating the physiology of oocytes. Long-term in vitro culture of CCs collected from patients undergoing controlled ovarian stimulation during in vitro fertilization procedure was conducted. Using microarray expression analysis, transcript levels were assessed on day 1, 7, 15, and 30 of culture. Apoptosis and aging of CCs strictly influence oocyte quality and subsequently the outcome of assisted reproductive technologies (ART). Thus, particular attention was paid to the analysis of genes involved in programmed cell death, aging, and apoptosis. Due to the detailed level of expression analysis of each of the 133 analyzed genes, three groups were selected: first with significantly decreased expression during the culture; second with the statistically lowest increase in expression; and third with the highest significant increase in expression. COL3A1, SFRP4, CTGF, HTR2B, VCAM1, TNFRSF11B genes, belonging to the third group, were identified as potential carriers of information on oocyte quality.

Chromosome Missegregation in Single Human Oocytes Is Related to the Age and Gene Expression Profile

The growing trend for women to postpone childbearing has resulted in a dramatic increase in the incidence of aneuploid pregnancies. Despite the importance to human reproductive health, the events precipitating female age-related meiotic errors are poorly understood. To gain new insight into the molecular basis of age-related chromosome missegregation in human oocytes, we combined the transcriptome profiles of twenty single oocytes (derived from females divided into two groups according to age <35 and ≥35 years) with their chromosome status obtained by array comparative genomic hybridization (aCGH). Furthermore, we compared the transcription profile of the single oocyte with the surrounding cumulus cells (CCs). RNA-seq data showed differences in gene expression between young and old oocytes. Dysregulated genes play a role in important biological processes such as gene transcription regulation, cytoskeleton organization, pathways related to RNA maturation and translation. The comparison of the transcription profile of the oocyte and the corresponding CCs highlighted the differential expression of genes belonging to the G protein-coupled receptor superfamily. Finally, we detected the loss of a X chromosome in two oocytes derived from women belonging to the ≥35 years age group. These aneuploidies may be caused by the detriment of REEP4, an endoplasmic reticulum protein, in women aged ≥35 years. Here we gained new insight into the complex regulatory circuit between the oocyte and the surrounding CCs and uncovered a new putative molecular basis of age-related chromosome missegregation in human oocytes.

Intrafollicular and systemic serotonin, oestradiol and progesterone concentrations in cycling mares

The hypothesis that a local serotonergic network might also exist in the follicle of mares remains poorly documented, with exception for humans and laboratory species. For this reason, the aim of the present study was to clarify this possibility, investigating intrafollicular serotonin concentrations of the cycling mare at ovulation time. Sixty ovaries collected from 30 clinically healthy mares of slaughterhouse meat production with clinically normal reproductive tracts after slaughtering were evaluated. Blood samples were taken prior to sacrifice. Follicles were classified in three categories in relation to size, as small (20-30 mm), medium (31-40 mm) and large (>41 mm), and the follicular fluid samples were extracted from each follicle. Intrafollicular and systemic serotonin (5-HT), oestradiol-17β (E₂ ) and progesterone (P₄ ) were determined by means of enzyme-linked immunosorbent assay and RIA, respectively. Intrafollicular 5-HT, E₂ and P₄ concentrations were higher than systemic ones (p < .05). 5-HT concentrations increased in larger compared to medium follicles, without differences compared to small size follicles (p < .05). 5-HT and E₂ (r = .79) and 5-HT and P₄ (r = .79; p < .05) were positively correlated. 5-HT and P₄ concentrations in follicular fluid increased progressively with the increase in follicular size (p < .05). Follicle diameter and E₂ (r = .85) and P₄ (r = .68) were correlated (p < .05). Since serotonin interacts with steroids, its role on steroidogenesis during growth of the dominant follicle may be suggested.

Functional signaling and gene regulatory networks between the oocyte and the surrounding cumulus cells

Background

The maturation and successful acquisition of developmental competence by an oocyte, the female gamete, during folliculogenesis is highly dependent on molecular interactions with somatic cells. Most of the cellular interactions identified, thus far, are modulated by growth factors, ions or metabolites. We hypothesized that this interaction is also modulated at the transcriptional level, which leads to the formation of gene regulatory networks between the oocyte and cumulus cells. We tested this hypothesis by analyzing transcriptome data from single oocytes and the surrounding cumulus cells collected from antral follicles employing an analytical framework to determine interdependencies at the transcript level.

Results

We overlapped our transcriptome data with putative protein-protein interactions and identified hundreds of ligand-receptor pairs that can transduce paracrine signaling between an oocyte and cumulus cells. We determined that 499 ligand-encoding genes expressed in oocytes and cumulus cells are functionally associated with transcription regulation (FDR < 0.05). Ligand-encoding genes with specific expression in oocytes or cumulus cells were enriched for biological functions that are likely associated with the coordinated formation of transzonal projections from cumulus cells that reach the oocyte’s membrane. Thousands of gene pairs exhibit significant linear co-expression (absolute correlation > 0.85, FDR < 1.8 × 10^− 5) patterns between oocytes and cumulus cells. Hundreds of co-expressing genes showed clustering patterns associated with biological functions (FDR < 0.5) necessary for a coordinated function between the oocyte and cumulus cells during folliculogenesis (i.e. regulation of transcription, translation, apoptosis, cell differentiation and transport).

Conclusion

Our analyses revealed a complex and functional gene regulatory circuit between the oocyte and surrounding cumulus cells. The regulatory profile of each cumulus-oocyte complex is likely associated with the oocytes’ developmental potential to derive an embryo.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4738-2) contains supplementary material, which is available to authorized users.

Sleep deprivation enhances peripheral serotonin secretion to regulate the large follicle steroidogenesis of rats

OBJECTIVE

Sleep deprivation (SD) leads to the disturbance of the estrous cycle. Serotonin, the levels of which increase with SD, has been shown to inhibit luteinizing hormone production and the receptor has been found in the follicles. In this study, the serotonin effect on preovulatory follicular steroidogenesis is investigated and the underlying mechanisms are elucidated.

MATERIALS AND METHODS

Female rats were subjected to SD for a time span of 1-4 days using the dish-over-water-method with a Rechtschaffen apparatus. Serum estradiol and serotonin concentrations were assessed; thereafter, they were evaluated with the effect of serotonin on the estradiol production and steroidogenic acute regulatory (StAR) protein expression in a serum-free culture system. Preovulatory follicles were dissected mechanically from the ovaries of 21-day-old rats, which induced follicle growth, and cultured for 24 hours with or without recombinant human follicle-stimulating hormone (FSH) in the presence or absence of serotonin.

RESULTS

SD, led to a significant decrease in serum estradiol concentrations, while serotonin concentrations were significantly elevated (all p < 0.05). Follicles were cultured with a constant dose of FSH (50 mIU/mL) and increasing doses of serotonin, estradiol production was reduced by 20%. The inhibitory effect of serotonin was concentration dependent. The addition of serotonin (0.1 μg/mL) decreased FSH-induced estradiol production and attenuated FSH-stimulated follicular StAR protein expression. The inhibitory effects of serotonin could be reduced by the serotonin receptor antagonist ketanserin.

CONCLUSION

These findings suggest that decreased serum estradiol concentrations in SD rats may be the result of serotonin-related inhibition of estradiol production and decreased large follicle expression of StAR protein.

Serotonin receptor 5-HT7 regulates morphology and migratory properties of dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells endowed with the unique ability to initiate adaptive immune responses upon inflammation. Inflammatory processes are often associated with an increased production of serotonin, which operates by activating specific receptors. However, the functional role of serotonin receptors in regulation of DC functions is poorly understood. Here we demonstrate that expression of serotonin receptor 5-HT7 (5-HT7R) as well as its down-stream effector Cdc42 is upregulated in DCs upon maturation. While DC maturation was independent of 5-HT7R, receptor stimulation affected DC morphology via Cdc42-mediated signaling. In addition, basal activity of 5-HT7R was required for the proper expression of the chemokine receptor CCR7, which is a key factor to control DC migration. Consistently, we observed that 5-HT7R enhances chemotactic motility of DCs in vitro by modulating their directionality and migration velocity. Accordingly, migration of DCs in murine colon explants was abolished after pharmacological receptor blockade. Our results indicate a critical role of 5-HT7R/Cdc42-mediated signaling in regulation of DC morphology and motility, suggesting 5-HT7R as a novel target for treatment of a variety of inflammatory and immune disorders.

Serotonin receptors are selectively expressed in the avian germ cells and early embryos

The expression of nine serotonin (5-HT) receptor transcripts was studied using reverse transcription polymerase chain reaction (RT-PCR) in germ cells, cleavage and gastrulation stages of Japanese quail, and qPCR for 5-HT3 and 5-HT4 receptors in oocytes and embryos. We show the presence/absence of nine serotonin transcripts known in birds for receptors 5-HT1A, 5-HT1F, 5-HT2B, 5-HT2C, 5-HT3, 5-HT4, 5-HT5A, 5-HT6 and 5-HT7A in avian germ cells and early embryos. The absence of 5-HT3 and 5-HT5A in primordial germ cells and of 5-HT3 and 5-HT7A in sperm is characteristic. All transcripts appeared in oocytes at all stages (except for 5-HT3 and 5-HT5A transcripts) and all were present in cleaving embryos and at gastrulation, except for 5-HT3, which was permanently observed as late as in stage 4. Interestingly, 5-HT3 and 5-HT5A receptors accumulated in 3-mm and F1 oocytes but were degraded at ovulation and started to be re-transcribed in cleavage stage II embryos and beyond. The selective appearance of 5-HT receptors in germ cells and early embryos supports the hypothesis that serotonin may act as a signalling molecule at early stages of germ line and embryo differentiation via individual receptors present during different stages, when specialized communication systems are not yet developed.

Serotonin receptor 6 mediates defective brain development in monoamine oxidase A-deficient mouse embryos

Monoamine oxidases A and B (MAO-A and MAO-B) are enzymes of the outer mitochondrial membrane that metabolize biogenic amines. In the adult central nervous system, MAOs have important functions for neurotransmitter homeostasis. Expression of MAO isoforms has been detected in the developing embryo. However, suppression of MAO-B does not induce developmental alterations. In contrast, targeted inhibition and knockdown of MAO-A expression (E7.5-E10.5) caused structural abnormalities in the brain. Here we explored the molecular mechanisms underlying defective brain development induced by MAO-A knockdown during in vitro embryogenesis. The developmental alterations were paralleled by diminished apoptotic activity in the affected neuronal structures. Moreover, dysfunctional MAO-A expression led to elevated levels of embryonic serotonin (5-hydroxytryptamine (5-HT)), and we found that knockdown of serotonin receptor-6 (5-Htr6) expression or pharmacologic inhibition of 5-Htr6 activity rescued the MAO-A knockdown phenotype and restored apoptotic activity in the developing brain. Our data suggest that excessive 5-Htr6 activation reduces activation of caspase-3 and -9 of the intrinsic apoptotic pathway and enhances expression of antiapoptotic proteins Bcl-2 and Bcl-XL. Moreover, we found that elevated 5-HT levels in MAO-A knockdown embryos coincided with an enhanced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and a reduction of proliferating cell numbers. In summary, our findings suggest that excessive 5-HT in MAO-A-deficient mouse embryos triggers cellular signaling cascades via 5-Htr6, which suppresses developmental apoptosis in the brain and thus induces developmental retardations.

Monoamine oxidases in development

Monoamine oxidases (MAOs) are flavoproteins of the outer mitochondrial membrane that catalyze the oxidative deamination of biogenic and xenobiotic amines. In mammals there are two isoforms (MAO-A and MAO-B) that can be distinguished on the basis of their substrate specificity and their sensitivity towards specific inhibitors. Both isoforms are expressed in most tissues, but their expression in the central nervous system and their ability to metabolize monoaminergic neurotransmitters have focused MAO research on the functionality of the mature brain. MAO activities have been related to neurodegenerative diseases as well as to neurological and psychiatric disorders. More recently evidence has been accumulating indicating that MAO isoforms are expressed not only in adult mammals, but also before birth, and that defective MAO expression induces developmental abnormalities in particular of the brain. This review is aimed at summarizing and critically evaluating the new findings on the developmental functions of MAO isoforms during embryogenesis.

Life without peripheral serotonin: insights from tryptophan hydroxylase 1 knockout mice reveal the existence of paracrine/autocrine serotonergic networks

Since its identification, 75 years ago, the monoamine serotonin (5-HT) has attracted considerable attention toward its role as a neurotransmitter in the central nervous system. Yet, increasing evidence, from a growing number of research groups, substantiates the fact that 5-HT regulates important nonneuronal functions. Peripheral 5-HT, synthesized by the enzyme tryptophan hydroxyase (Tph) in intestinal cells, was assumed to be distributed throughout the entire body by blood platelets and to behave as a pleiotropic hormone. A decade ago, generation of a mouse model devoid of peripheral 5-HT lead to the discovery of a second isoform of the enzyme Tph and also suggested that 5-HT might act as a local regulator in various organs. The objective of this review is to highlight the newly discovered functions played by the monoamine using the Tph1 KO murine model and to outline current findings that led to the discovery of complete serotonergic systems in unexpected organs. Within an organ, both the presence of local Tph enzymatic activity and serotonergic components are of particular importance as they support the view that 5-HT meets the criteria to be qualified as a monoamine with a paracrine/autocrine function.

Effects of systemic administration or intrabursal injection of serotonin on puberty, first ovulation and follicular development in rats

To elucidate the role of serotonin in the onset of puberty, the effects of both systemic and in-ovarian bursa administration of serotonin on the neuroendocrine mechanism that modulates the onset of puberty, follicular development and first ovulation were evaluated. Two experiments were carried out. For the first, 25 or 37.5 mg kg–1 of bodyweight of serotonin creatinine sulfate was administered by a subcutaneous route to 30-day-old female rats. In the second experiment, serotonin creatinine sulfate was administered directly into the ovarian bursa of 34-day-old female rats. Systemic administration of 25 or 37.5 mg kg–1 of serotonin creatinine sulfate induced a delay in the ages of vaginal opening and first vaginal oestrus, a decrease in the number of ovulating animals, and serum concentrations of FSH, LH, oestradiol and progesterone. An increase in the number of Class 3 (>500 μm) and atretic follicles was observed in the ovaries of these animals. The administration of serotonin creatinine sulfate in the ovarian bursa did not modify the onset of puberty and ovulation, but a reduced serum concentration of oestradiol was observed. Our results suggest that serotonin acts on the components of the hypothalamus–hypophysis–ovary axis by modulating follicular development, ovarian functions and the onset of puberty.

Inverse correlation of intracellular calcium and cyclic AMP levels in renal cell carcinoma

Renal cell carcinoma (RCC) is the most common renal tumour in adults. Altered levels of secondary messengers, that is, intracellular calcium and cyclic AMP (cAMP), have been implicated in the pathogenesis of various malignancies. In the present study, we measured levels of intracellular calcium and cAMP in RCC. The intracellular calcium level was significantly reduced, whereas the cAMP level was significantly augmented in RCC as compared with adjacent grossly normal renal parenchyma.

High-fat diet causes an imbalance in the colonic serotonergic system promoting adipose tissue enlargement and dysplasia in rats

A high-fat (HF) diet, the serotonergic system and stromal elements have all been implicated in colon carcinogenesis. We investigated whether the colonic serotonergic system could play a main role in the development of colonic dysplasia and stromal reactivity in carcinogen-treated rats under HF diet. For this, dimethylhydrazine-treated rats were fed with standard diet and a HF diet. Fat distribution was quantified by computerized tomography exam, serotonergic activity was analyzed by high-performance liquid chromatography, gene expression, and immunohistochemistry, which along with histopathological technique enabled us to enumerate dysplasia, microvessels density, cell proliferation and COX-2 expression. We found that the HF diet induced an increase in the amount of visceral adipose tissue, even without expressive changes in the average body weight. This was correlated with a loss of serotonergic balance in colon tissue. Moreover, the HF diet promoted dysplasia and microvessel density in association with increased proliferation and COX-2 expression within pericryptal colonic stroma. Our current findings suggest that a HF diet promotes the enlargement of adipose tissue via loss of control in colon serotonergic activity, which enhances colonic dysplasia by supporting microvessel development.

Biogenic monoamines in preimplantation development

BACKGROUND

The involvement of biogenic monoamines in early ('preneural') embryogenesis has been well documented in lower vertebrates, but much less information is available about the role of these molecules in the earliest stages of development in mammals, including humans.

METHODS

Databases (PubMed, ISI Web of Knowledge and Scopus) were searched for studies relating to biogenic monoamines functioning in early embryos. The available data on the expression of histamine, serotonin and adrenergic receptors during mammalian preimplantation development were summarized, and the potential roles of biogenic monoamines in very early pregnancy were discussed.

RESULTS

The roles of biogenic monoamines in mammalian preimplantation embryo development can be diverse, depending on the embryo developmental stage, and the physiological status of the maternal organism. Several receptors for biogenic monoamines are expressed and biologically functional in cells of preimplantation embryos. Activation of histamine receptors can play a role in embryo implantation and trophoblast invasion. Activation of adrenergic and serotonin receptors can influence proliferation and survival of early embryonic cells.

CONCLUSIONS

Biogenic monoamines can play an important role in physiological conditions, contributing to embryo-maternal interactions, or can influence the early embryo under unfavorable or pathological conditions (e.g. in maternal stress, or in women taking certain antidepressants, anti-migraine or anti-ulcer drugs).

Fluoxetine induces preventive and complex effects against colon cancer development in epithelial and stromal areas in rats

Fluoxetine (FLX) is a drug commonly used as antidepressant. However, its effects on tumorigenesis remain controversial. Aiming to evaluate the effects of FLX treatment on early malignant changes, we analyzed serotonin (5-HT) metabolism and recognition, aberrant crypt foci (ACF), proliferative process, microvessels, vascular endothelial growth factor (VEGF), and cyclooxygenase-2 (COX-2) expression in colon tissue. Male Wistar rats received a daily FLX-gavage (30mgkg(-1)) and, a single dose of 1,2 dimethylhydrazine (DMH; i.p., 125mgkg(-1)). After 6 weeks of FLX-treatment, our results revealed that FLX and nor-fluoxetine (N-FLX) are present in colon tissue, which was related to significant increase in serotonin (5-HT) levels (P<0.05) possibly through a blockade in SERT mRNA (serotonin reuptake transporter; P<0.05) resulting in lower 5-hydroxyindoleacetic acid (5-HIAA) levels (P<0.01) and, 5-HT2C receptor mRNA expressions. FLX-treatment decreased dysplastic ACF development (P<0.01) and proliferative process (P<0.001) in epithelia. We observed a significant decrease in the development of malignant microvessels (P<0.05), VEGF (P<0.001), and COX-2 expression (P<0.01). These findings suggest that FLX may have oncostatic effects on carcinogenic colon tissue, probably due to its modulatory activity on 5-HT metabolism and/or its ability to reduce colonic malignant events.

Physiological endpoints for potential SSRI interactions in fish

Selective serotonin reuptake inhibitors (SSRIs) are among the pharmaceutical compounds frequently detected in sewage treatment plant effluents and surface waters, albeit at very low concentrations, and have therefore become a focus of interest as environmental pollutants. These neuroactive drugs are primarily used in the treatment of depression but have also found broader use as medication for other neurological dysfunctions, consequently resulting in a steady increase of prescriptions worldwide. SSRIs, via inhibition of the serotonin (5-hydroxytryptamine, 5-HT) reuptake mechanism, induce an increase in extracellular 5-HT concentration within the central nervous system of mammals. The phylogenetically ancient and highly conserved neurotransmitter and neurohormone 5-HT has been found in invertebrates and vertebrates, although its specific physiological role and mode of action is unknown for many species. Consequently, it is difficult to assess the impact of chronic SSRI exposure in the environment, especially in the aquatic ecosystem. In view of this, the current knowledge of the functions of 5-HT in fish physiology is reviewed and, via comparison to the physiological role and function of 5-HT in mammals, a characterization of the potential impact of chronic SSRI exposure on fish is provided. Moreover, the insight on the physiological function of 5-HT strongly suggests that the experimental approaches currently used are inadequate if not entirely improper for routine environmental risk assessment of pharmaceuticals (e.g., SSRIs), as relevant endpoints are not assessed or impossible to determine.

Differing mechanisms of cAMP- versus seawater-induced oocyte maturation in marine nemertean worms II. The roles of tyrosine kinases and phosphatases

Instead of blocking oocyte maturation as it does in most animals, cAMP causes oocytes of marine nemertean worms to initiate maturation (=germinal vesicle breakdown, "GVBD"). To characterize cAMP-induced GVBD in nemerteans, inhibitors of tyrosine kinase signaling were tested on Cerebratulus sp. oocytes that had been incubated in cAMP-elevating drugs versus seawater (SW) alone. Such tests yielded similar results for Src-like tyrosine kinase blockers, as the inhibitors prevented mitogen-activated protein kinase (MAPK) activation without stopping either GVBD or maturation-promoting factor (MPF) activation in both SW and cAMP-elevating treatments. Alternatively, genistein, a general tyrosine kinase antagonist, and piceatannol, an inhibitor of the tyrosine kinase Syk, reduced GVBD and MAPK/MPF activities in SW-, but not cAMP-induced maturation. Similarly, inhibitors of the human epidermal growth factor receptor-2 (HER-2) tyrosine kinase prevented GVBD and MAPK/MPF activations in oocytes treated with SW, but not with cAMP-elevating drugs. Antagonists of either protein tyrosine phosphatases (PTPs) or the dual-specificity phosphatase Cdc25 also reduced GVBD and MAPK/MPF activities in SW-treated oocytes without generally affecting cAMP-induced maturation. Collectively, these data suggest cAMP triggers GVBD via pathways that do not require MAPK activation or several components of tyrosine kinase signaling. In addition, such differences in tyrosine kinase cascades, coupled with the dissimilar patterns of Ser/Thr kinase signaling described in the accompanying study, indicate that nemertean oocytes are capable of utilizing multiple mechanisms to activate MPF during GVBD.