Essential actions of melatonin in protecting the ovary from oxidative damage

Melatonin increases superoxide dismutase 2 (SOD2) levels and improves rat ovarian graft function after transplantation

BACKGROUND

Ovarian cryopreservation is a promising technique despite being hindered by damage from freezing and thawing. Melatonin can mitigate this outcome.

OBJECTIVE

This study aimed to evaluate the effect of melatonin on the follicular dynamics of ovarian tissue in a cryopreserved cell culture.

METHODS

Three-month-old adult female Wistar rats (n = 24) weighing approximately 250 g were oophorectomized and divided into two groups (n = 12): the control group (CG) and the melatonin group (MG). In the CG, slow cryopreservation was performed according to the standard protocol with Medium M2 and dimethyl sulfoxide (DMSO). In MG, melatonin diluted in ethyl alcohol vehicle at a concentration of 0.1 μm was added to the culture medium. In both groups, the ovaries were cryopreserved by slow freezing and kept in liquid nitrogen for 24 h. Subsequently, after thawing, the ovaries were reimplanted in the retroperitoneum, one on each side of the great vessels (inferior vena cava and aorta). After 30 days, the animals were euthanized during the diestrus phase; then, the grafts were removed and processed for histomorphometric and immunohistochemical analyses, whereas the blood was subjected to biochemical analysis. Student's t test was used to assess the difference between the groups.

RESULTS

The FSH levels in MG (83.79 ± 32.37) were lower than those in CG (120.52 ± 36.59), p = 0.03. The FSH/AMH ratios were also lower in MG (3.53 ± 1.13) than in CG (6.52 ± 2.85), p = 0.001. The SOD2 immunoexpression was higher in MG than in CG regarding all parameters except for the degenerated follicles (follicular cells and internal thecal cells): CG (16.80 ± 4.80 [13.36-20.24]) and MG (14.91 ± 4.04 [12.01-17.79]) p = 0.351. Statistically, the difference in intact follicles (theca + interstitium) between CG (6.60 ± 2.59 [4.75-8.45]) and MG (9.31 ± 3.09 [7.09-11.51]) was significant (p = 0.049), with a small difference in the expression of regular antral follicles.

CONCLUSIONS

Melatonin can improve the quality of cryopreserved tissues, as evidenced in this study, and the evaluation of cryopreserved ovarian grafts, as shown in the melatonin group with better hormonal parameters and greater immunohistochemical expression of the SOD2 antioxidant. Thus, damage is reduced during cryopreservation and transplantation is improved.

Effects of Dietary Melatonin on Antioxidant Capacity, Immune Defense, and Intestinal Microbiota in Red Swamp Crayfish (Procambarus clarkii)

The aim of this study was to investigate the effects of melatonin (MT) feed supplementation on the antioxidant capacity, immune defense, and intestinal flora in Procambarus clarkii (P. clarkii). Six groups of P. clarkii were fed test feeds containing different levels of MT: 0 mg/kg (control), 22.5, 41.2, 82.7, 165.1, and 329.2 mg/kg for a duration of 2 months. The specific growth rate, hepatosomatic index, and condition factor were recorded highest in the test group of shrimp fed an MT concentration of 165.1 mg/kg. Compared to the control group, the rate of apoptosis was lower in hepatopancreas cells of P. clarkii supplemented with high concentrations of MT. Analyses of antioxidant capacity and immune-response-related enzymes in the hepatopancreas indicated that dietary supplementation of MT significantly augmented both the antioxidant system and immune responses. Dietary MT supplementation significantly increased the expression levels of antioxidant-immunity-related genes and decreased the expression levels of genes linked to apoptosis. Dietary MT was associated with an elevation in the abundance of the Firmicutes and a reduction in the abundance of the Proteobacteria in the intestines; besides, resulting in an increase in the abundance of beneficial bacteria, such as Lactobacilli. The broken-line model indicated that the suitable MT concentration was 154.09-157.09 mg/kg. MT supplementation enhanced the growth performance of P. clarkii, exerting a positive influence on the intestinal microbiota, and bolstered both immune response and disease resistance. Thus, this study offered novel perspectives regarding the application of dietary MT supplementation within the aquaculture field.

Melatonin improves mouse oocyte quality from 2-ethylhexyl diphenyl phosphate-induced toxicity by enhancing mitochondrial function

2-Ethylhexyl diphenyl phosphate (EHDPP) is a representative organophosphorus flame retardant (OPFR) that has garnered attention due to its widespread use and potential adverse effects. EHDPP exhibits cytotoxicity, genotoxicity, developmental toxicity, and endocrine disruption. However, the toxicity of EHDPP in mammalian oocytes and the underlying mechanisms remain poorly understood. Melatonin is a natural free radical scavenger that has demonstrated cytoprotective properties. In this study, we investigated the effect of EHDPP on mouse oocytes in vitro culture system and evaluated the rescue effect of melatonin on oocytes exposed to EHDPP. Our results indicated that EHDPP disrupted oocyte maturation, resulting in the majority of oocytes arrested at the metaphase I (MI) stage, accompanied by cytoskeletal damage and elevated levels of reactive oxygen species (ROS). Nevertheless, melatonin supplementation partially rescued EHDPP-induced mouse oocyte maturation impairment. Results of single-cell RNA sequencing (scRNA-seq) analysis elucidated potential mechanisms underlying these protective effects. According to the results of scRNA-seq, we conducted further tests and found that EHDPP primarily disrupts mitochondrial distribution and function, kinetochore-microtubule (K-MT) attachment, DNA damage, apoptosis, and histone modification, which were rescued upon the supplementation of melatonin. This study reveals the mechanisms of EHDPP on female reproduction and indicates the efficacy of melatonin as a therapeutic intervention for EHDPP-induced defects in mouse oocytes.

Mitochondria of Porcine Oocytes Synthesize Melatonin, Which Improves Their In Vitro Maturation and Embryonic Development

The in vitro maturation efficiency of porcine oocytes is relatively low, and this limits the production of in vitro porcine embryos. Since melatonin is involved in mammalian reproductive physiology, in this study, we have explored whether endogenously produced melatonin can help in porcine oocyte in vitro maturation. We have found, for the first time in the literature, that mitochondria are the major sites for melatonin biosynthesis in porcine oocytes. This mitochondrially originated melatonin reduces ROS production and increases the activity of the mitochondrial respiratory electron transport chain, mitochondrial biogenesis, mitochondrial membrane potential, and ATP production. Therefore, melatonin improves the quality of oocytes and their in vitro maturation. In contrast, the reduced melatonin level caused by siRNA to knockdown AANAT (siAANAT) is associated with the abnormal distribution of mitochondria, decreasing the ATP level of porcine oocytes and inhibiting their in vitro maturation. These abnormalities can be rescued by melatonin supplementation. In addition, we found that siAANAT switches the mitochondrial oxidative phosphorylation to glycolysis, a Warburg effect. This metabolic alteration can also be corrected by melatonin supplementation. All these activities of melatonin appear to be mediated by its membrane receptors since the non-selective melatonin receptor antagonist Luzindole can blunt the effects of melatonin. Taken together, the mitochondria of porcine oocytes can synthesize melatonin and improve the quality of oocyte maturation. These results provide an insight from a novel aspect to study oocyte maturation under in vitro conditions.

Ovarian overexpression of ASMT gene increases follicle numbers in transgenic sheep: Association with lipid metabolism

Melatonin plays an important role in mammalian reproductive activities, to further understand the effects of endogenous melatonin on functions of ovary, the transgenic sheep with overexpression of melatonin synthetic enzyme gene ASMT in ovary were generated. The results showed that total melatonin content in follicular fluid of transgenic sheep was significantly greater than that in the wild type. Accordingly, the follicle numbers of transgenic sheep were also significantly greater than those in the WT. The results of follicular fluid metabolites sequencing showed that compared with WT, the differential metabolites of the transgenic sheep were significantly enriched in several signaling pathways, the largest number of metabolites was lipid metabolism pathway and the main differential metabolites were lipids and lipoid molecules. SMART-seq2 were used to analyze the oocytes and granulosa cells of transgenic sheep and WT sheep. The main differential enrichment pathway was metabolic pathway, in which lipid metabolism genes accounted for the majority. In conclusion, this is the first report to show that ovary overexpression of ASMT increased local melatonin production and follicle numbers. These results may imply that ASMT plays an important role in follicle development and formation, and melatonin intervention may be a potential method to promote this process.

Effect of melatonin on developmental competence, mitochondrial distribution, and intensity of fresh and vitrified/thawed in vitro matured buffalo oocytes

BACKGROUND

In livestock breeding, oocyte cryopreservation is crucial for preserving and transferring superior genetic traits. This study was conducted to examine the additional effect of melatonin to maturation and vitrification media on the in vitro developmental capacity, mitochondrial distribution, and intensity of buffalo oocytes. The study involved obtaining ovaries from a slaughterhouse and conducting two phases. In the first phase, high-quality oocytes were incubated in a maturation medium with or without 10-9M melatonin for 22 h (at 38.5°C in 5% CO2). Matured oocytes were fertilized in vitro and cultured in SOF media for seven days. In the second phase, vitrified in vitro matured oocytes were stored in vitrified media (basic media (BM) containing a combination of cryoprotectants (20% Ethyl Glycol and 20% Dimethyl sulfoxide), with or without melatonin, and then stored in liquid nitrogen. Normal vitrified/thawed oocytes were fertilized in vitro and cultured as described. Finally, the matured oocytes from the fresh and vitrified/thawed groups, both with and without melatonin, were stained using DAPI and Mitotracker red to detect their viability (nuclear maturation), mitochondrial intensity, and distribution using a confocal microscope. The study found that adding 10-9M melatonin to the maturation media significantly increased maturation (85.47%), fertilization rate (84.21%)cleavage (89.58%), and transferable embryo (48.83%) rates compared to the group without melatonin (69.85%,79.88%, 75.55%, and 37.25% respectively). Besides that, the addition of melatonin to the vitrification media improved the recovery rate of normal oocytes (83.75%), as well as the cleavage (61.80%) and transferable embryo (27.00%) rates when compared to the vitrified TCM group (67.46%, 51.40%, and 17.00%, respectively). The diffuse mitochondrial distribution was higher in fresh with melatonin (TCM + Mel) (80%) and vitrified with melatonin (VS2 + Mel groups) (76.70%), Furthermore, within the same group, while the mitochondrial intensity was higher in the TCM + Mel group (1698.60) than other group. In conclusion, Melatonin supplementation improves the developmental competence and mitochondrial distribution in buffalo oocytes in both cases(in vitro maturation and vitrification).

Role of Melatonin in Ovarian Function

Melatonin is a hormone mainly produced by the pineal gland in the absence of light stimuli. The light, in fact, hits the retina, which sends a signal to the suprachiasmatic nucleus, which inhibits the synthesis of the hormone by the epiphysis. Mostly by interacting with MT1/MT2 membrane receptors, melatonin performs various physiological actions, among which are its regulation of the sleep-wake cycle and its control of the immune system. One of its best known functions is its non-enzymatic antioxidant action, which is independent from binding with receptors and occurs by electron donation. The hormone is also an indicator of the photoperiod in seasonally reproducing mammals, which are divided into long-day and short-day breeders according to the time of year in which they are sexually active and fertile. It is known that melatonin acts at the hypothalamic-pituitary-gonadal axis level in many species. In particular, it inhibits the hypothalamic release of GnRH, with a consequent alteration of FSH and LH levels. The present paper mainly aims to review the ovarian effect of melatonin.

The Role of Melatonin to Ameliorate Oxidative Stress in Sperm Cells

It is widely accepted that oxidative stress (OS) coming from a wide variety of causes has detrimental effects on male fertility. Antioxidants could have a significant role in the treatment of male infertility, and the current systematic review on the role of melatonin to ameliorate OS clearly shows that improvement of semen parameters follows melatonin supplementation. Although melatonin has considerable promise, further studies are needed to clarify its ability to preserve or restore semen quality under stress conditions in varied species. The present review examines the actions of melatonin via receptor subtypes and its function in the context of OS across male vertebrates.

Ovarian tissue cryopreservation and transplantation: a review on reactive oxygen species generation and antioxidant therapy

Cancer is the leading cause of death worldwide. Fortunately, the survival rate of cancer continues to rise, owing to advances in cancer treatments. However, these treatments are gonadotoxic and cause infertility. Ovarian tissue cryopreservation and transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with significant follicle loss and an accompanying short lifespan of the grafts. There has been a decade of research in cryopreservation-induced oxidative stress in single cells with significant successes in mitigating this major source of loss of viability. However, despite its success elsewhere and beyond a few promising experiments, little attention has been paid to this key aspect of OTCT-induced damage. As more and more clinical practices adopt OTCT for fertility preservation, it is a critical time to review oxidative stress as a cause of damage and to outline potential ameliorative interventions. Here we give an overview of the application of OTCT for female fertility preservation and existing challenges; clarify the potential contribution of oxidative stress in ovarian follicle loss; and highlight potential ability of antioxidant treatments to mitigate the OTCT-induced injuries that might be of interest to cryobiologists and reproductive clinicians.

The Aging Ovary and the Tales Learned Since Fetal Development

BACKGROUND

While the term "aging" implies a process typically associated with later life, the consequences of ovarian aging are evident by the time a woman reaches her forties, and sometimes earlier. This is due to a gradual decline in the quantity and quality of oocytes which occurs over a woman's reproductive lifespan. Indeed, the reproductive potential of the ovary is established even before birth, as the proper formation and assembly of the ovarian germ cell population during fetal life determines the lifetime endowment of oocytes and follicles. In the ovary, sophisticated molecular processes have been identified that regulate the timing of ovarian aging and these are critical to ensuring follicular maintenance.

SUMMARY

The mechanisms thought to contribute to overall aging have been summarized under the term the "hallmarks of aging" and include such processes as DNA damage, mitochondrial dysfunction, telomere attrition, genomic instability, and stem cell exhaustion, among others. Similarly, in the ovary, molecular processes have been identified that regulate the timing of ovarian aging and these are critical to ensuring follicular maintenance. In this review, we outline critical processes involved in ovarian aging, highlight major achievements for treatment of ovarian aging, and discuss ongoing questions and areas of debate.

KEY MESSAGES

Ovarian aging is recognized as what may be a complex process in which age, genetics, environment, and many other factors contribute to the size and depletion of the follicle pool. The putative hallmarks of reproductive aging outlined herein include a diversity of plausible processes contributing to the depletion of the ovarian reserve. More research is needed to clarify if and to what extent these putative regulators do in fact govern follicle and oocyte behavior, and how these signals might be integrated in order to control the overall pattern of ovarian aging.

Premature ovarian insufficiency: a review on the role of oxidative stress and the application of antioxidants

Normal levels of reactive oxygen species (ROS) play an important role in regulating follicular growth, angiogenesis and sex hormone synthesis in ovarian tissue. When the balance between ROS and antioxidants is disrupted, however, it can cause serious consequences of oxidative stress (OS), and the quantity and quality of oocytes will decline. Therefore, this review discusses the interrelationship between OS and premature ovarian insufficiency (POI), the potential mechanisms and the methods by which antioxidants can improve POI through controlling the level of OS. We found that OS can mediate changes in genetic materials, signal pathways, transcription factors and ovarian microenvironment, resulting in abnormal apoptosis of ovarian granulosa cells (GCs) and abnormal meiosis as well as decreased mitochondrial Deoxyribonucleic Acid(mtDNA) and other changes, thus accelerating the process of ovarian aging. However, antioxidants, mesenchymal stem cells (MSCs), biological enzymes and other antioxidants can delay the disease process of POI by reducing the ROS level in vivo.

Effects of melatonin on development and hormone secretion of sheep theca cells in vitro

Theca cells (TCs) play a unique role in the structure and function of the ovary. They are not only the structural basis of the follicle but also the androgen-secreting cells in female mammals, which can affect the normal development and atresia of the follicle. The results showed that melatonin receptor (MTR) MT1 and MT2 were expressed on sheep TCs. In the present study, the effects of different concentrations of MT at 0, 10^-10, 10^-8, 10^-6 and 10^-4 M/L on sheep TCs with regards to the antioxidant levels, proliferation, apoptosis and steroid hormone secretion were investigated. The results showed that in sheep TCs, all concentrations of MT significantly decreased reactive oxygen species (ROS) concentration and BAX expression; increased Cat, Sod1, and BCL-2 expression. The proliferation viability of TCs was significantly inhibited in all groups except for 10^-10 M/L MT, and the expression of cyclin D1 and CDK4 was significantly reduced. MT significantly increased StAR expression and progesterone secretion in TCs, but there was no significant effect on androgen secretion and CYP11A1, CYP17A1 and 3β-HSD expression in all groups. MT-induced progesterone secretion was completely inhibited by Luzindole (a nonspecific MT1 and MT2 inhibitor) and partially inhibited by 4p-PDOT (specific MT2 inhibitor). MT-induced progesterone secretion can be inhibited by LY294002 (PI3K/AKT pathway inhibitor). This study indicated that MT inhibits apoptosis and proliferation of in vitro cultured sheep TCs, which has implications for slowing ovarian atresia and aging. MT activates the PI3K/Akt pathway to mediate the synthesis and secretion of progesterone by TCs. This study provides a basis for further exploration of the role of TCs on follicle development and ovarian steroid hormone secretion.

Analysis of MTNR1A Genetic Polymorphisms and Their Association with the Reproductive Performance Parameters in Two Mediterranean Sheep Breeds

Sheep farming plays an important economic role, and it contributes to the livelihoods of many rural poor in several regions worldwide and particularly in Tunisia. Therefore, the steady improvement of ewes' reproductive performance is a pressing need. The MTNR1A gene has been identified as an important candidate gene that plays a key role in sheep reproduction and its sexual inactivity. It is involved in the control of photoperiod-induced seasonality mediated by melatonin secretion. The aim of this study was to identify SNPs in the MTNR1A gene in two Tunisian breeds, Barbarine (B) and Queue Fine de l'Ouest (QFO). DNA extracted from the blood of 77 adult ewes was sequenced. Selected ewes were exposed to adult fertile rams. A total of 26 SNPs were detected; 15 SNPs in the promoter region and 11 SNPs in the exon II were observed in both (B) and (QFO) breeds. The SNP rs602330706 in exon II is a novel SNP detected for the first time only in the (B) breed. The SNPs rs430181568 and rs40738822721 (SNP18 and SNP20 in our study, respectively) were totally linked in this study and can be considered a single marker. DTL was associated with SNP18 and SNP20 in (B) ewes (p < 0.05); however, no significant difference was detected between the three genotypes (G/G, G/A, and A/A) at these two SNPs. Fertility rate and litter size parameters were not affected by SNP18 and SNP20. There was an association between these two polymorphisms and (B) lambs' birth weights (p < 0.05). Furthermore, the ewes with the A/A genotype gave birth to lambs with a higher weight compared to the other two genotypes for this breed (p < 0.05). There was not an association between SNP 18 and SNP20 and (QFO) ewes' reproductive parameters. These results might be considered in future sheep selection programs for reproductive genetic improvement.

Coprophagy Prevention Affects the Reproductive Performance in New Zealand White Rabbits Is Mediated through Nox4-ROS-NFκB Pathway

Coprophagy is of great significance to the growth, development, and reproductive performance of rabbits. This study is aimed at exploring the effect of coprophagy on the reproductive performance of New Zealand white rabbits by coprophagy prevention (CP). The results showed that CP treatment significantly decreased the growth and development performance of female rabbits and the live birth rate of embryos. The results of blood biochemical indexes showed that CP treatment significantly increased the contents of serum ALB, ALP, and MDA, while serum SOD activity was significantly decreased. Transcriptome analysis showed that GO terms were mainly enriched in transport function and reproductive function after CP treatment. In addition, KEGG results showed that inflammation related signal pathways were activated and the expression level of genes related to tight junction proteins was downregulated by CP treatment. Concurrently, western blot further confirmed the results of KEGG. In short, fecal feeding is an important survival strategy for some small rodents, coprophagy prevention will affect the inflammatory level of the body, change the oxidative stress level of the body, and then activate NOX4-ROS-NF-κB pathway, increase the expression level of adhesion protein ICAM-1 and VCAM-1, lead to the damage of uterine epithelial barrier, and then affect the reproductive performance of rabbits.

The genomic response of human granulosa cells (KGN) to melatonin and specific agonists/antagonists to the melatonin receptors

Melatonin is a known modulator of follicle development; it acts through several molecular cascades via binding to its two specific receptors MT1 and MT2. Even though it is believed that melatonin can modulate granulosa cell (GC) functions, there is still limited knowledge of how it can act in human GC through MT1 and MT2 and which one is more implicated in the effects of melatonin on the metabolic processes in the dominant follicle. To better characterize the roles of these receptors on the effects of melatonin on follicular development, human granulosa-like tumor cells (KGN) were treated with specific melatonin receptor agonists and antagonists, and gene expression was analyzed with RNA-seq technology. Following appropriate normalization and the application of a fold change cut-off of 1.5 (FC 1.5, p ≤ 0.05) for each treatment, lists of the principal differentially expressed genes (DEGs) are generated. Analysis of major upstream regulators suggested that the MT1 receptor may be involved in the melatonin antiproliferative effect by reprogramming the metabolism of human GC by activating the PKB signaling pathway. Our data suggest that melatonin may act complementary through both MT1 and MT2 receptors to modulate human GC steroidogenesis, proliferation, and differentiation. However, MT2 receptors may be the ones implicated in transducing the effects of melatonin on the prevention of GC luteinization and follicle atresia at the antral follicular stage through stimulating the PKA pathway.

Effect of Different Concentrations of Melatonin on Ram Epididymal Spermatozoa Recovered Post-mortem under Oxidative Stress Conditions and Storage at 4 °C

The current study examines the protective effects of different melatonin concentrations on fresh ram epididymis spermatozoa after post-mortem recovery under normal and oxidative stress conditions and during liquid preservation (4^o C) at different times (24, 48, and 72h). The testes were obtained from a local slaughterhouse during the breeding season. Spermatozoa were isolated from cauda epididymidis. In experiment 1, the effects of adding different concentrations of melatonin (0, 15, 60, and 240 μg/mL) under normal and oxidative stress conditions were evaluated. Fifty μM of hydrogen peroxide was used to induce oxidative stress. Also, in experiment 2, the spermatozoa samples were chilled to 4^o C and stored for 72 h. Sperm total motility, viability, membrane, DNA integrity, and morphological abnormality were evaluated at 0, 24, 48, and 72 h after cooling storage. In experiment 1, melatonin treatment preserved viability increased TAC and SOD activities, and reduced MDA levels compared to control. Also, melatonin reduced the harmful effects of H2O2 under induced oxidative stress. In experiment 2, Melatonin at concentrations of 15 and 60 g/mL greatly increased sperm viability after 3 days of cold storage. Furthermore, it could have a significant protective effect on the motility of cooled sperm. Melatonin supplementation preserved higher sperm membrane integrity at concentrations of 15 and 60μg/mL, DNA integrity at a concentration of 15μg/mL, and abnormality at a concentration of 60μg/mL after 3 days of storage. The results suggest that melatonin can be used to reduce the adverse effects of induced oxidative stress in spermatozoa. Furthermore, ram epididymal spermatozoa could be stored at 4 °C for 72 h when treated with melatonin.

Human fertility and sleep disturbances: A narrative review

INTRODUCTION

Many factors may be hidden behind the global fertility decline observed in Western countries. Alongside the progressively increased age of infertile couples, environmental and behavioural factors, including non-optimal lifestyle habits, should be considered. Among these, sleep disorders have been suggested to be linked to human fertility.

METHODS

This is a narrative review, describing first sleep physiology, its disturbances, and the tools able to quantify sleep dysfunction. Then, we consider all available studies aimed at investigating the connection between sleep disorders and human fertility, providing a comprehensive view on this topic.

RESULTS

Forty-two studies investigating the relationship between sleep habits and human reproduction were included. All the published evidence was grouped according to the aspect of human fertility considered, i.e. i) female reproductive functions, ii) male reproductive functions, iii) natural conception and iv) assisted reproduction. For each of the sub-groups considered, the connection between sleep dysregulation and human fertility was classified according to specific sleep characteristics, such as sleep duration, quality, and habits. In addition, possible physio-pathological mechanisms proposed to support the link between sleep and fertility were summarized.

CONCLUSION

This review summarizes the most relevant findings about the intricate and still largely unknown network of molecular pathways involved in the regulation of circadian homeostasis, to which sleep contributes, essential for reproductive physiology. Thus, many mechanisms seem correlate sleep disorders to reproductive health, such as adrenal activation, circadian dysregulation, and genetic influences. This review highlights the need to properly designed trials on the topic.

The effect of melatonin on the mouse ameloblast-lineage cell line ALCs

Melatonin plays a critical role in promoting the proliferation of osteoblasts and the growth and development of dental papilla cells. However, the effect and mechanism of melatonin on the growth and development of ALCs still need to be explored. CCK8 assay was used for the evaluation of cell numbers. qRT-PCR was used to identify the differentially expressed genes in ALCs after melatonin treatment. The number and morphology of ALCs were investigated by confocal microscopy. Alkaline phosphatase assay and Alizarin red S staining were used for measuring mineralization. Then, we focused on observing the crucial factors of the signaling pathway by RNA-seq and qRT-PCR. Melatonin limited the cell number of ALCs in a dose-dependent manner and promoted the production of actin fibers. A high concentration of melatonin significantly promoted the mRNA levels of enamel matrix proteins and the formation of mineralized nodules. RNA-seq data showed that Wnt signaling pathway may be involved in the differentiation of ALCs under the influence of melatonin. This study suggests that melatonin plays a regulatory role in the cell number, differentiation, and mineralization of the ALCs, and then shows the relationship between the Wnt signaling pathway with the ALCs under melatonin.

Women with polycystic ovary syndrome (PCOS) have reduced melatonin concentrations in their follicles and have mild sleep disturbances

Background

Polycystic ovary syndrome (PCOS) is a common gynecologic disorder related to abnormal circadian rhythm. Therefore, we aimed to find whether the level of melatonin, a rhythm regulating hormone changed in the ovarian microenvironment in this disease.

Methods

The melatonin concentrations in follicular fluid (FF) were measured in 35 PCOS and 36 non-PCOS women undergoing in vitro fertilization (IVF) treatment.

Results

The FF melatonin concentration was significantly lower in PCOS women than non-PCOS women (p = 0.045) and it was found positively correlated with serum basal FSH level (r = 0.308, p = 0.013). In IVF procedures, there was no significant difference in the fertilization rate of oocytes between the two groups, but the high-quality embryogenesis rate on the third day of the PCOS group was significantly lower than that of the control group (p = 0.042), which showed a weak positive correlation with the FF melatonin concentration (r_s = 0.240, p = 0.044). Furthermore, there was no significant difference in overall pregnancy outcome. The PSQI questionnaire showed that sleep disorders were more likely to exist in the PCOS group, though there was no significant difference.

Conclusion

The obtained results suggested PCOS women had lower melatonin concentrations in the ovarian microenvironment.

Comparison of melatonin, oxytetracycline, and N-acetylcysteine pre-treatments in autologous intraperitoneal ovarian transplantation in rats

This study was aimed at investigating the effects of melatonin, oxytetracycline and N-acetylcysteine on the ovarian follicle reserves and surface epithelium in autologous intraperitoneal ovarian transplantation in rats. Thirty adult female Wistar Albino were selected and randomly divided into six groups (n = 5). Group 1, which was the control group, only had their abdomens opened and closed while Group 2 underwent ovarian transplantation. Group 3, 4, 5 and 6 received 20 μg/kg/IM melatonin, 10 mg/kg/IM oxytetracycline, 150 mg/kg/IP N-Asetil sistein (NAC) and 1% ethanol respectively 15 min before the ovarian transplantation. Vaginal cytology was performed to monitor the estrus phase and the follicle reserve and changes in the surface epithelium were histopathologically evaluated during the preparations. Moreover, cellular apoptosis in tissues was evaluated with immunofluorescence staining of Bcl-2 and Bax. The Bax/Bcl-2 ratio was then calculated as the mean fluorescence intensity (MFI) of Bax and Bcl-2 MFI. Dysplastic change was found only significantly higher in the transplantation group (G2) (p < 0.01). Histopathologically, it was found that the follicle reserve was preserved significantly in the oxytetracycline and melatonin treated group (G3, G4) (p < 0.01). It was also observed that the oxytetracycline treated group (G4) were able to show better preventive effects against dysplastic changes of the surface epithelium. Moreover, the melatonin treated group depicted a low Bax/Bcl-2 ratio compared to the group that only underwent transplantation (G2) (p < 0.01). This study indicated that oxytetracycline and melatonin might be more effective than N-acetylcysteine in protecting against oxidative stress during ovarian transplantation.

Melatonin alleviates insulin resistance through the PI3K/AKT signaling pathway in ovary granulosa cells of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine gynecological disorder. Insulin resistance (IR) is a major cause of PCOS. Melatonin, a critical endogenous hormone, has beneficial effects on the female reproductive system. This study aims to investigate the molecular effect of melatonin on IR in human ovarian granulosa cells (GCs). Hormone levels of the subjects were determined through clinical examination. The expression levels of insulin receptor substrate (IRS)-1 and glucose transporter (GLUT4) in GCs from PCOS patients and a human granulosa cell line (SVOG) were examined using qRT-PCR and western blot. The IR cell model was established by inducing SVOG cells with palmitic acid (PA). IR was detected in GCs of PCOS patients and SVOG by measuring glucose content and glucose uptake. Cell viability and apoptosis levels were detected by CCK-8 assay and flow cytometry. PI3K/Akt pathway expression in SVOG was assessed by western blot. PCOS patients had higher levels of luteinizing hormone (LH), testosterone, and LH/follicle-stimulating hormone. PA decreased cell viability, promoted apoptosis, and reduced glucose uptake in SVOG cells. IRS-1 and GLUT4 mRNA and protein expression was downregulated, and glucose uptake capacity was reduced in PCOS GCs and SVOG cells. Melatonin significantly upregulated IRS-1 and GLUT4 expression, downregulated p-IRS-1 (Ser307), and improved glucose uptake in PCOS patients' GCs and SVOG cells. PA decreased PI3K and Akt phosphorylation, whereas melatonin increased p-PI3K and p-Akt levels. Melatonin can reduce IR in GCs and PA-induced SVOG cells via the PI3K/Akt signaling pathway, providing more evidence for treating polycystic ovary syndrome.

Potentiating the Benefits of Melatonin through Chemical Functionalization: Possible Impact on Multifactorial Neurodegenerative Disorders

Although melatonin is an astonishing molecule, it is possible that chemistry will help in the discovery of new compounds derived from it that may exceed our expectations regarding antioxidant protection and perhaps even neuroprotection. This review briefly summarizes the significant amount of data gathered to date regarding the multiple health benefits of melatonin and related compounds. This review also highlights some of the most recent directions in the discovery of multifunctional pharmaceuticals intended to act as one-molecule multiple-target drugs with potential use in multifactorial diseases, including neurodegenerative disorders. Herein, we discuss the beneficial activities of melatonin derivatives reported to date, in addition to computational strategies to rationally design new derivatives by functionalization of the melatonin molecular framework. It is hoped that this review will promote more investigations on the subject from both experimental and theoretical perspectives.

Melatonin Attenuates Cyclophosphamide-Induced Primordial Follicle Loss by Interaction with MT1 Receptor and Modulation of PTEN/Akt/FOXO3a Proteins in the Mouse Ovary

This study evaluated the protective effect of melatonin before cyclophosphamide administration on ovarian function and its potential mechanism in a mouse model. Two studies were performed. In the first, mice were pretreated with melatonin (10, 20, or 30 mg/kg body weight, i.p.) once daily for 3 days, followed by injection with a single dose of cyclophosphamide (200 mg/kg body weight, i.p.) 30 min after the last melatonin injection. The second study analyzed whether melatonin type 1 and/or 2 receptors mediate the effects of melatonin on the ovary through administration of non-selective MT₁/MT₂ antagonist (luzindole) or selective MT₂ antagonist (4-PPDOT) before the treatment with melatonin plus cyclophosphamide. After treatment groups, the ovaries were harvested and destined to histology, immunohistochemistry, and fluorescence analyses. Lastly, we examined the p-PTEN, p-Akt, and p-FOXO3a participation in the protective effect of melatonin in cyclophosphamide-induced ovarian damage. Results demonstrated that pretreatment with 20 mg/kg melatonin before cyclophosphamide administration showed more morphologically normal follicles, attenuated primordial follicle loss, decreased growing follicle atresia and mitochondrial damage, and increased GSH concentrations. Furthermore, treatment with luzindole blocked the protective effects of melatonin against the damage caused by cyclophosphamide. Additionally, pretreatment with 20 mg/kg melatonin regulated the PTEN/Akt/FOXO3a signaling pathway components after cyclophosphamide treatment. In conclusion, pretreatment with 20 mg/kg melatonin prevented primordial follicle loss and reduced apoptosis and oxidative damage in the mouse ovary during experimental chemotherapy with cyclophosphamide. Furthermore, the MT₁ receptor and PTEN/Akt/FOXO3a proteins mediated these cytoprotective effects.

Adipose-Derived Mesenchymal Stem Cells: A Promising Tool in the Treatment of pre mature ovarian failure

Despite being rare, primary ovarian insufficiency (POI) is a significant cause of infertility and deficiency of ovarian hormone in women. Several health risks are also associated with POI, which include dry eye syndrome, reduced density of bones and enhanced fracture risks, troublesome menopausal symptoms, early development of cardiovascular disease, and psychological effects such as declined cognition, reduced perceived psychological support, anxiety, and depression. Replacing premenopausal levels of ovarian sex steroids through proper hormone replacement therapy could improve the quality of life for POI women and ameliorate related health risks. Herein, POI and its complications, in addition to hormone replacement therapies, which are safe and effective, are discussed. It is proposed that the use of HRT) Hormone replacement therapy (formulations which mimic normal production of ovarian hormones could reduce POI-associated morbidity rates if they are continued by the age 50, which is approximately the natural age of menopause. Particular populations of POI women are also addressed, which include those with enhanced risk of ovarian or breast cancer, those with Turner syndrome, those approaching natural menopause, and those who are breastfeeding. It is generally predicted that stem cell-based therapies would be both safe and effective. In fact, several types of cells have been described as safe, though their effectiveness and therapeutic application are yet to be defined. Several factors exist which could affect the results of treatment, such as cell handling, ex-vivo preparation strategies, variations in tissue of origin, potency, and immunocompatibility. Accordingly, cell types potentially effective in regenerative medicine could be recognized. Notably, products of MSCs from various sources of tissues show different levels of regenerative capabilities. The ultimate focus of the review is on adipose tissue-derive MCSs (ADMSCs), which possess exceptional features such as general availability, great ability to proliferate and differentiate, immunomodulatory capabilities, and low immunogenicity.

Melatonin and Myo-Inositol: Supporting Reproduction from the Oocyte to Birth

Human pregnancy is a sequence of events finely tuned by several molecular interactions that come with a new birth. The precise interlocking of these events affecting the reproductive system guarantees safe embryo formation and fetal development. In this scenario, melatonin and myo-inositol seem to be pivotal not only in the physiology of the reproduction process, but also in the promotion of positive gestational outcomes. Evidence demonstrates that melatonin, beyond the role of circadian rhythm management, is a key controller of human reproductive functions. Similarly, as the most representative member of the inositol’s family, myo-inositol is essential in ensuring correct advancing of reproductive cellular events. The molecular crosstalk mediated by these two species is directly regulated by their availability in the human body. To date, biological implications of unbalanced amounts of melatonin and myo-inositol in each pregnancy step are growing the idea that these molecules actively contribute to reduce negative outcomes and improve the fertilization rate. Clinical data suggest that melatonin and myo-inositol may constitute an optimal dietary supplementation to sustain safe human gestation and a new potential way to prevent pregnancy-associated pathologies.

Research progress of melatonin (MT) in improving ovarian function: a review of the current status

Melatonin (MT) is an endogenous hormone mainly synthesized by pineal cells, which has strong endogenous effects of eliminating free radicals and resisting oxidative damages. Melatonin (MT) can not only regulate the body’s seasonal and circadian rhythms; but also delay ovarian senescence, regulate ovarian biological rhythm, promote follicles formation, and improve oocyte quality and fertilization rate. This review aimd to provide evidence concerning the synthesis and distribution, ovarian function, and role of MT in development of follicles and oocytes. Moreover, the role of MT as antioxidative, participating in biological rhythm regulation, was also reviewed. Furthermore, the effects of MT on various ovarian related diseases were analyzed, particularly for the ovarian aging and polycystic ovary syndrome (PCOS).

Luzindole and 4P-PDOT block the effect of melatonin on bovine granulosa cell apoptosis and cell cycle depending on its concentration

Granulosa cells play an essential physiological role in mediating the follicle development and survival or apoptosis of granulosa cells dictate the follicle development or atresia. The aim of this study was to investigate the role of high dose (10-5 M) and low dose (10-9 M) melatonin in bovine granulosa cells, and assess whether MT1 and MT2 inhibiter affect granulosa cells response to melatonin. We found that the high dose (10-5 M) and low dose (10-9 M) both could act as an essential role in modulating granulosa cells apoptosis, cell cycle and antioxidant. The beneficial effect could be related to that melatonin promoted the expression of Bcl2, Bcl-xl, SOD1 and GPX4, and inhibited Bax, caspase-3 and p53 expression. Moreover P21 expression was decreased in granulosa cells treated with the high dose (10-5 M) melatonin and increased in that treated with the low dose (10-9 M) melatonin. To further reveal the role of MT1 and MT2 in mediating the effect of melatonin on granulosa cells apoptosis, cell cycle and antioxidant, we found that the luzindole and 4P-PDOT did not affect the effect of high dose (10-5 M) melatonin on regulating Bcl2, Bax, caspase-3, SOD1, GPX4 and p53 expression, while blocked its effect on modulating Bcl-xl and P21expression. However, luzindole and 4P-PDOT disturbed the effect of low dose (10-9 M) melatonin on regulating Bcl2, Bax, caspase-3, Bcl-xl, SOD1, GPX4, and p53 expression. In conclusion, these results reveal that the effect of low dose (10-9 M) melatonin on granulosa cells apoptosis are mediated by MT1 and MT2, and the high dose (10-5 M) melatonin affect the granulosa cells apoptosis by other pathway, besides MT1 and MT2. Moreover MT1 and MT2 may work in concert to modulate bovine granulosa cells function by regulating cellular progression and apoptosis.

Pretreatment with melatonin improves ovarian tissue cryopreservation for transplantation

BACKGROUD

Melatonin has anti-inflammatory and antioxidative actions at the mitochondrial level. This indole-containing molecule may protect ovarian grafts during the process of cryopreservation. Therefore, we aimed to determine whether melatonin pretreatment improves rat ovarian graft quality.

METHODS

Twenty-six female rats were allocated to two study groups of thirteen animals each: 1) control group: ovaries cryopreserved using the standard protocol; and 2) melatonin group: ovaries cryopreserved in a medium with melatonin. Ten rats of each group were submitted to 24-h freezing, and whole ovaries autologous and avascular transplantation with retroperitoneal placement. After postoperative (PO) day 15, daily vaginal smears were obtained for estrous cycle characterization. Between PO days 30 and 35, the animals were euthanized and ovarian grafts were recovered for histological and immunohistochemical (Ki-67, cleaved caspase-3, TUNEL, von Willebrand factor, estrogen, and progesterone receptors) analyses. The ovaries of the three remaining rats from each group were studied immediately after thawing to assess the effects of cryopreservation. ANOVA and Tukey's tests were used and the rejection level of the null hypothesis was set at 0.05 or 5% (p < 0.05).

RESULTS

Melatonin promoted faster restart of the estrous cycle and increased the expression of mature follicles, collagen type I, von Willebrand factor, Ki-67, and cleaved caspase-3 on corpora lutea and estrogen receptors in the ovaries as compared to control. There was a reduction in apoptosis by TUNEL on follicles, corpora lutea, and collagen type III.

CONCLUSION

Based on the evaluated parameters, melatonin may promote the quality of ovarian grafts. Reproductive function enhancement should be further studied.

Roles of melatonin in the teleost ovary: A review of the current status

Melatonin, the neurohormone mainly synthesized in and secreted from the pineal gland of vertebrates following a circadian rhythm, is an important factor regulating various physiological processes, including reproduction. Recent data indicate that melatonin is also synthesized in the ovary and that it acts directly at the level of the ovary to modulate ovarian physiology. In some teleosts, melatonin is reported to affect ovarian steroidogenesis. The direct action of melatonin on the ovary could be a possible factor promoting oocyte maturation in teleosts. A role for melatonin in follicle rupture during ovulation in the teleost medaka has recently emerged. In addition, melatonin is suggested to affect oocyte maturation by its antioxidant activity. However, the molecular mechanisms underlying these direct effects of melatonin are largely unknown.

Melatonin induction of HSP90 expression exerts cryoprotective effect on ovarian tissue

Our previous study revealed that melatonin (MLT) protected the quality of cryopreserved ovarian tissues in mice. This work was carried out to examine the role of MLT in inducing HSP90 expression of ovarian tissue for achieving cryoprotection. Pieces of ovarian tissues were obtained from 50 female rats treated with MLT at 0, 0.001, 0.01, 0.1, and 1 mM, respectively. After cryopreservation-thawing, HSP90 mRNA and protein level were evaluated using qRT-PCR and western blot. The qRT-PCR results revealed that HSP90 mRNA expression was significantly (p < 0.01) upregulated in MLT-treated groups in comparison with the controls (0 mM). Western blot revealed higher HSP90 protein expression in MLT-treated groups compared to control group (0 mM), thus further confirming that MLT positively affected HSP90 expression. Moreover, 0.1 mM MLT had better effects than other concentrations of MLT. Conclusively, findings in the present work provide a feasible technology for improving cryopreserved ovarian tissue quality through the addition of MLT to elicit HSP90 expression.

Importance of Melatonin in Assisted Reproductive Technology and Ovarian Aging

Melatonin is probably produced in all cells but is only secreted by the pineal gland. The pineal secretion of melatonin is determined by the light–dark cycle, and it is only released at night. Melatonin regulates biological rhythms via its receptors located in the suprachiasmatic nuclei of the hypothalamus. Melatonin also has strong antioxidant activities to scavenge free radicals such as reactive oxygen species (ROS). The direct free radical scavenging actions are receptor independent. ROS play an important role in reproductive function including in the ovulatory process. However, excessive ROS can also have an adverse effect on oocytes because of oxidative stress, thereby causing infertility. It is becoming clear that melatonin is located in the ovarian follicular fluid and in the oocytes themselves, which protects these cells from oxidative damage as well as having other beneficial actions in oocyte maturation, fertilization, and embryo development. Trials on humans have investigated the improvement of outcomes of assisted reproductive technology (ART), such as in vitro fertilization and embryo transfer (IVF-ET), by way of administering melatonin to patients suffering from infertility. In addition, clinical research has examined melatonin as an anti-aging molecule via its antioxidative actions, and its relationship with the aging diseases, e.g., Alzheimer’s and Parkinson’s disease, is also underway. Melatonin may also reduce ovarian aging, which is a major issue in assisted reproductive technology. This review explains the relationship between melatonin and human reproductive function, as well as the clinical applications expected to improve the outcomes of assisted reproductive technology such as IVF, while also discussing possibilities for melatonin in preventing ovarian aging.

Effects of feeding melatonin during proestrus and early gestation to gilts and parity 1 sows to minimize effects of seasonal infertility1

This study tested whether supplemental melatonin given to mimic the extended nighttime melatonin pattern observed in the higher fertility winter season could minimize infertility during summer and fall in swine. Exogenous melatonin was fed during periods coinciding with follicle selection, corpus luteum formation, pregnancy recognition, and early embryo survival. Experiments were conducted at a commercial farm in 12 sequential replicates. In Exp. 1a, mature gilts (n = 420) that had expressed a second estrus were assigned by weight to receive once daily oral Melatonin (MEL, 3 mg) or Control (CON, placebo) at 1400 h for 3 wk starting before insemination at third estrus. In Exp. 1b, parity 1 sows (n = 470) were randomly assigned by lactation length to receive MEL or CON for 3 wk, starting 2 d before weaning. Follicles, estrus, pregnancy, and farrowing data were analyzed for the main effects of treatment, season (4-wk periods), and their interaction. Environmental measures were also analyzed for reproductive responses. In Exp. 1a, there was no effect (P > 0.10) of MEL on age at third estrus (203 d), follicle size after 7 d of treatment (5.0 mm), estrous cycle length (22.6 d), return to service (9.2%), farrowing rate (FR, 80.0%), or total born pigs (TB, 13.6). However, there was an effect of season (P = 0.03) on number of follicles and on gilts expressing estrus within 23 d of the previous estrus (P < 0.005). In Exp. 1b, there was no effect of MEL (P > 0.10) on follicle measures, wean to estrous interval, FR (84.0%), or TB (13.0). But MEL (73.5%) reduced (P = 0.03) estrous expression within 7 d of weaning compared with CON (82.0%) and season (P = 0.001) decreased FR by ~14.0% during mid summer. Also, gilts and parity 1 sows exposed to low light intensity (<45 lx) during breeding had reduced conception (-8%) and farrowing (-15%) rates, compared with higher light intensity. Similarly, high temperatures (>25 °C) during breeding also reduced gilt conception rates by 7%. Although there was clear evidence of seasonal fertility failures in gilts and sows, MEL treatment did not improve fertility in gilts and reduced estrus in parity 1 sows. It is possible that differences in lighting and thermal environments before breeding could explain the differential response to MEL in sows and gilts.

Effects of melatonin on ovarian reserve in cigarette smoking: an experimental study

INTRODUCTION

The aim of the study was to investigate whether melatonin has a protective effect against diminished ovarian reserve induced by smoking.

MATERIAL AND METHODS

Seventy-two female Wistar-Albino rats were divided into 6 groups: group I (room air), group II (chronic cigarette smoking), group III (room air + 10 mg/kg subcutaneous melatonin), group IV (room air + 20 mg/kg subcutaneous melatonin), group V (chronic cigarette smoking + 10 mg/kg subcutaneous melatonin), group VI (chronic cigarette smoking + 20 mg/kg subcutaneous melatonin). For 45 days, rats were exposed to cigarette smoke through a smoking machine, then subcutaneous melatonin was administered. Apoptotic index, immunohistochemical scoring, ovarian follicle counting, ovarian tissue and serum malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) analyses were carried out.

RESULTS

All of the primordial, primary, secondary and mature follicle numbers were found to be significantly lowered in study groups. Increased HSCORE with anti-caspase-3 staining and a high follicular apoptotic index were demonstrated in the smoking group. Serum and ovarian tissue levels of MDA were found to be elevated with smoke exposure whereas lower MDA levels were determined in melatonin treated groups. Serum and tissue levels of SOD, GPx and CAT were shown to be reduced in the smoking group in comparison with melatonin treated and control groups. 20 mg/kg melatonin administration in the smoking group revealed significantly decreased HSCOREs and apoptotic indices.

CONCLUSIONS

Cigarette smoking has been definitely shown to be associated with impaired ovarian reserve with respect to significantly diminished numbers of primordial, primary, secondary and mature follicles. Dose-related treatment of melatonin in smokers may provide an evidently reduced apoptotic index and improved antioxidant activity in tissue.

Does night work affect age at which menopause occurs?

PURPOSE OF REVIEW

To delineate the current state of evidence on the impact of night shift work on age at natural menopause.

RECENT FINDINGS

The only direct evidence is from a single observational study, which indicates that women who work night shifts are at moderately higher risk for earlier menopause and that this risk is more pronounced among younger women. Underlying biological mechanisms have yet to be sufficiently substantiated. A long-held line of inquiry, most strongly propagated by the observed link between night shift work and female breast cancer, is the 'Light at Night' hypothesis, which suggests melatonin-mediated circadian disruption as a potential regulator of reproductive signaling in women. Supporting evidence is found from observations of changes in endogenous melatonin production among night working women or in response to light exposure, and corresponding changes in endogenous ovarian hormone levels and modulated menstrual patterns, among other indications of altered central ovulation-governing processes. Susceptibility to night shift work may be modified by chronotype.

SUMMARY

This review summarizes the literature related to night work and ovulatory regulation in humans, prioritizing population-based evidence to provide motivation for the study of circadian disruption and night shift work as a regulator of menopausal timing.

Melatonin protects against Epirubicin-induced ovarian damage

One major side effect of chemotherapy that young women with cancer suffer from is ovarian damage. Therefore, it is necessary to study the pathogenesis of chemotherapeutic drugs in order to develop pharmaceutical agents to preserve fertility. Epirubicin is one of the commonly used chemotherapy drugs for breast cancer patients. This research explored the side effects of epirubicin in mice. We found that epirubicin significantly reduced the body weight, the weight of the ovaries and uteri, and the pups' number, while melatonin, which is extremely resistant to oxidation, significantly reduced these damages. Moreover, co-treatment with melatonin prevented epirubicin-induced decrease in E<inf>2</inf> and progesterone, and the loss of follicles. Mechanism study showed that melatonin significantly reduced the levels of proapoptotic genes p53, Caspase3, and Caspase9 while it upregulated antiapoptotic factors Bcl-2 and Bcl2l1, and antioxidant genes superoxide dismutase 1 and catalase compared with the epirubicin group. In addition, melatonin markedly reduced reactive oxygen species (ROS) and the transcription of Caspase12 and Chop, which is vital in endoplasmic reticulum stress (ERS)-mediated apoptosis. These results indicate melatonin protects against epirubicin-induced ovarian damage by reducing ROS-induced ERS. Therefore, melatonin has a therapeutic potential for the protection of ovarian function and preservation of fertility during chemotherapy.

Melatonin effects on ovarian follicular cells: a systematic review

Melatonin is known for its effects on both the sleep and reproductive system of mammals. The latter has melatonin receptors type 1 and 2, which act to regulate, among other things, cyclic AMP. Notwithstanding all the literature data, there is still no sound knowledge or a clear understanding of the hormone's action on the physiology of ovarian follicular cells. OBJECTIVE To review and evaluate studies about melatonin action on the ovarian granulosa/theca interna cells from the literature. METHODS The systematic review was carried out according to the PRISMA recommendations. The MEDLINE and Cochrane primary databases were consulted with the use of specific terms. There was no limitation on language or publication year. RESULTS Seven papers about melatonin action on granulosa cells were selected. The following can be attributed to the hormone's effects: a) progesterone increase in culture medium; b) increased estrogen production; c) antagonistic action on estrogen; d) improvement in cell quality resulting in improved embryo and higher pregnancy rates; e) improved cell proliferation via MAPK; f) reduction of free radicals. Nevertheless, there are contrarian papers reporting a reduction in progesterone production. Melatonin interferes in sex steroid production, boosting progesterone output. Such action may help improve oocyte quality.

Melatonin in Medicinal and Food Plants: Occurrence, Bioavailability, and Health Potential for Humans

Melatonin is a widespread molecule among living organisms involved in multiple biological, hormonal, and physiological processes at cellular, tissue, and organic levels. It is well-known for its ability to cross the blood–brain barrier, and renowned antioxidant effects, acting as a free radical scavenger, up-regulating antioxidant enzymes, reducing mitochondrial electron leakage, and interfering with proinflammatory signaling pathways. Detected in various medicinal and food plants, its concentration is widely variable. Plant generative organs (e.g., flowers, fruits), and especially seeds, have been proposed as having the highest melatonin concentrations, markedly higher than those found in vertebrate tissues. In addition, seeds are also rich in other substances (lipids, sugars, and proteins), constituting the energetic reserve for a potentially growing seedling and beneficial for the human diet. Thus, given that dietary melatonin is absorbed in the gastrointestinal tract and transported into the bloodstream, the ingestion of medicinal and plant foods by mammals as a source of melatonin may be conceived as a key step in serum melatonin modulation and, consequently, health promotion.

The usefulness of melatonin in the field of obstetrics and gynecology

Disorders of the female reproductive system, including those associated with hormone regulation, fertility rate and fetal health, are issues of great concern worldwide. More recently, melatonin supplementation has been suggested as a therapeutic approach in gynecological practice. In both animal models and in women, melatonin supplementation suggests a therapeutic and preventative potential, effects attributed mainly to its antioxidant properties and action as hormone modulator. The aim of this literature review is to further investigate the evidence available on the effects of melatonin supplementation in animal and human studies, focusing on its potential application to gynecology. Melatonin-containing supplements are easily found in online and high street retailers, and despite its supplementation deemed to be relatively safe, no consensus has been reached on effective dosage and supplementation period. Short term supplementation studies, of up to six months, suggest that a daily posology of 2-18 mg of melatonin may have the potential to improve fertility rate, oocyte quality, maturation and number of embryos. However, the evidence available so far on the effects of melatonin supplementation covering gestational age and gestational outcomes is very scarce. Clinical trials and longer-term supplementation studies are required to assess any clinical outcome associated with melatonin supplementation in the field of gynecology.

Melatonin Abrogates the Anti-Developmental Effect of the AKT Inhibitor SH6 in Bovine Oocytes and Embryos

Melatonin, a nighttime-secreted antioxidant hormone produced by the pineal gland, and AKT, a serine/threonine-specific protein kinase, have been identified as regulators for several cellular processes essential for reproduction. The current study aimed to investigate the potential interplay between melatonin and AKT in bovine oocytes in the context of embryo development. Results showed that the inclusion of SH6, a specific AKT inhibitor, during in vitro maturation (IVM) significantly reduced oocyte maturation, cumulus cell expansion, cleavage, and blastocyst development that were rescued upon addition of melatonin. Oocytes treated with SH6 in the presence of melatonin showed lower levels of reactive oxygen species (ROS) and blastocysts developed exhibited low apoptosis while the mitochondrial profile was significantly improved compared to the SH6-treated group. The RT-qPCR results showed up-regulation of the mRNA of maturation-, mitochondrial-, and cumulus expansion-related genes including GDF-9, BMP-15, MARF1, ATPase, ATP5F1E, POLG2, HAS2, TNFAIP6, and PTGS2 and down-regulation of Bcl-2 associated X apoptosis regulator (BAX), caspase 3, and p21 involved in apoptosis and cell cycle arrest in melatonin-SH6 co-treated group compared to SH6 sole treatment. The immunofluorescence showed high levels of caspase 3 and caspase 9, and low AKT phosphorylation in the SH6-treated group compared to the control and melatonin-SH6 co-treatment. Taken together, our results showed the importance of both melatonin and AKT for overall embryonic developmental processes and, for the first time, we report that melatonin could neutralize the deleterious consequences of AKT inhibition, suggesting a potential role in regulation of AKT signaling in bovine oocytes.

Melatonin alleviates β-zearalenol and HT-2 toxin-induced apoptosis and oxidative stress in bovine ovarian granulosa cells

β-zearalenol (β-zol) and HT-2 are mycotoxins which cause apoptosis and oxidative stress in mammalian reproductive cells. Melatonin is an endogenous antioxidant involved in apoptosis and oxidative stress-related activities. This study investigated the effects of β-zol and HT-2 on bovine ovarian granulosa cells (BGCs), and how melatonin may counteract these effects. β-zol and HT-2 inhibited cell proliferation in a dose-dependent manner, and induced apoptosis of BGCs. They also yielded upregulation of the apoptosis-related genes Bax/Bcl-2 and Caspase3 and phosphorylation of p38MAPK. Increases in intracellular ROS were observed along with higher levels of mRNA anti-oxidation markers SOD1, SOD2, and CAT. SOD1, SOD2, malonaldehyde (MDA), and glutathione peroxidase (GSH-px) activities increased, as did the levels of SOD1 and SOD2 proteins. All of these effects were reduced or entirely attenuated in BGCs pre-treated with melatonin. Our results demonstrate that melatonin has protective effects against mycotoxin-induced apoptosis and oxidative stress in BGCs.

Melatonin protects rabbit spermatozoa from cryo-damage via decreasing oxidative stress

Mammalian spermatozoa are highly susceptible to reactive oxygen species (ROS) stress. The aim of the present study was to investigate whether and how melatonin protects rabbit spermatozoa against ROS stress during cryopreservation. Semen was diluted with Tris-citrate-glucose extender in presence of different concentrations of melatonin. It was observed that addition of 0.1 mM melatonin significantly improved spermatozoa motility, membrane integrity, acrosome integrity, mitochondrial membrane potential as well as AMP-activated protein kinase (AMPK) phosphorylation. Meanwhile, the lipid peroxidation (LPO), ROS levels and apoptosis of post-thaw spermatozoa were reduced in presence of melatonin. Interestingly, when fresh spermatozoa were incubated with 100 μM H₂O₂, addition of 0.1 mM melatonin significantly decreased the oxidative damage compared to the H₂O₂ treatment, whereas addition of luzindole, an MT1 receptor inhibitor, decrease the effect of melatonin in spermatozoa. It was observed that the glutathione (GSH) content and activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were significantly increased with addition of melatonin during cryopreservation. In conclusion, addition of melatonin to the freezing extender protects rabbit spermatozoa against ROS attack by enhancing AMPK phosphorylation for increasing the antioxidative defense.

Higher melatonin in the follicle fluid and MT2 expression in the granulosa cells contribute to the OHSS occurrence

BACKGROUND

Ovarian hyperstimulation syndrome (OHSS) is a common and severe complication for patients undergoing IVF/ICSI-ET. Melatonin widely participates in the regulation of female reproductive endocrine activity. However, whether melatonin participates in the progression of OHSS is largely unknown. This study aims to identify the predictive value of follicular fluid (FF) melatonin for OHSS establishment and the underlying mechanism.

METHODS

All participants of this case-control study were enrolled at the Reproductive Medicine Center located in the First Affiliated Hospital of Zhengzhou University in China from January to October in 2017. Quantitative real-time PCR and western blot were used to examine the mRNA and protein levels. Primary granulosa cells were extracted and cultured for in vitro studies. Melatonin concentration was measured by ELISA. Logistic analysis and receiver-operating characteristic (ROC) curves were used to evaluate the predicting value of melatonin on OHSS occurrence.

MAIN OUTCOME MEASURES

The expression level of melatonin receptor 2 (MT2), P450 aromatase cytochrome (aromatase), vascular endothelial growth factor (VEGF), and inducible nitric oxide synthase (iNOS) mRNA in human primary granulosa cells. The concentration of melatonin in FF. The predicting value of melatonin on OHSS and the cut-off value of the prediction.

RESULTS

FF melatonin concentrations were significantly higher in patients with OHSS compared to non-OHSS group (35.94 ± 10.18 ng/mL vs 23.93 ± 10.94 ng/mL, p<0.001). The expression of MT2 mRNA (p = 0.0459) and protein in granulosa cells was also significantly higher in the OHSS group. When using a cut-off level of 27.52 ng/ml, the sensitivity and specificity of FF melatonin to predict OHSS was 84.6 and 74.0%, respectively (p < 0.0001). We also found that melatonin could up-regulates aromatase mRNA, VEGF mRNA expression and down-regulates iNOS mRNA expression in the granulosa cells.

CONCLUSION

OHSS patients have higher melatonin in the FF as well as higher MT2 expression in the granulosa cells. The melatonin in FF might be used as an effective predictor for the occurrence of OHSS.

Rotating night shift work and menopausal age

STUDY QUESTION

How are rotating night shift schedules associated with age at menopause among a large, national cohort of shift working nurses?

SUMMARY ANSWER

Our findings suggest that working rotating night shifts with sufficient frequency may modestly accelerate reproductive senescence among women who may already be predisposed to earlier menopause.

WHAT IS KNOWN ALREADY

Younger age at menopause has been associated with increased risk of adverse health outcomes, particularly those linked to reproduction. Night work has been associated with reproductive dysfunction, including disruption of menstrual cycle patterns.

STUDY DESIGN, SIZE, DURATION

This cohort study was conducted among 80 840 women of the Nurses' Health Study 2 (NHS2), with prospective follow-up from 1991 through 2013. Loss-to-follow-up of the NHS2 is estimated to be <10%.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We assessed the association between cumulative and current rotating night shift work and age at natural menopause over 22 years of follow-up (1991-2013). Cox proportional hazards models were used to estimate hazard ratios (HR) for menopause, adjusted for age, smoking status, body mass index, physical activity, alcohol consumption, reproductive factors and exogenous hormone use.

MAIN RESULTS AND THE ROLE OF CHANCE

Over follow-up, 27 456 women (34%) reached natural menopause. Women who worked 20 or more months of rotating night shifts in the prior 2-year had an increased risk of earlier menopause (multivariable-adjusted (MV)-HR = 1.09, 95% CI: 1.02-1.16) compared to women without rotating night shift work. This risk was stronger among women undergoing menopause or otherwise censored under age 45 years (MV-HR = 1.25, 95% CI: 1.08-1.46), than it was for those continuing in the study when >45 years old (MV-HR = 1.05, 95% CI: 0.99-1.13). Working 10 or more years of cumulative rotating night work was also associated with higher risk of menopause among women reaching menopause under age 45 (MV-HR10-19 years = 1.22, 95% CI: 1.03-1.44; MV-HR≥20 years = 1.73, 95% CI: 0.90-3.35), though not over the age of 45 years (MV-HR10-19 years = 1.04, 95% CI: 0.99-1.10; MV-HR≥20 years = 1.01, 95% CI: 0.89-1.15).

LIMITATIONS, REASONS FOR CAUTION

The degree to which observed effects of rotating night shifts on age at natural menopause are due to circadian disruption, rather than fatigue and stress associated with working more demanding schedules, is uncertain due to potential residual confounding by these factors.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to assess the effects of night work on menopausal timing among a larger national cohort of shift working women. Women already prone to earlier menopause may further truncate their reproductive lifetime by working schedules comprising day as well as night shifts.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Center for Disease Control and Prevention/The National Institute for Occupational Safety and Health Grant 5R01OH009803 (PI: Schernhammer E), as well as UM1 CA176726 from the National Institute of Health. The funding sources had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the article; and decision to submit the article for publication. The authors have no conflicts of interest.

Effects of melatonin on oocyte developmental competence and the role of melatonin receptor 1 in juvenile goats

Melatonin enhances in vitro embryo development in several species by improving the oocyte developmental competence during in vitro maturation (IVM). Melatonin has a wide range of actions, from scavenging reactive oxygen species (ROS) to regulating gene expression, and it can also act by way of melatonin receptors. The aim of this study was to determine the mechanism of action of melatonin during the IVM of juvenile goat oocytes and the role of the membrane receptors. Melatonin receptor 1 was immunolocalized in cumulus cells and oocytes before and after 24 hr of IVM. The effect of melatonin on oocyte developmental competence was tested in three experimental IVM groups: (a) control, (b) 10^-7  M melatonin, and (c) 10^-7  M melatonin +10^-7  M luzindole (an inhibitor of both melatonin receptors). After IVM oocytes were assessed for ROS levels, mitochondrial activity, adenosine 5'-triphosphate (ATP) concentration and relative gene expression (ACTB, SLC1A1, SOD1, GPx1, BAX, DNMT1, GCLC and GDF9). IVM-oocytes were in vitro fertilized and cultured under conventional conditions. Blastocyst rate and quality (differential cell count) were assessed at 8 days post-fertilization. Melatonin decreased ROS levels, increased mitochondrial activity and ATP content and increased blastocyst quality compared to control group (55.8 vs. 30.4 inner cell mass ICM, p < 0.05). There was no effect on the relative gene expression due to treatment with melatonin. In conclusion, we have showed that melatonin improves oocyte developmental competence in juvenile goats by reducing ROS levels and improving mitochondrial activity.

Melatonin and its metabolites vs oxidative stress: From individual actions to collective protection

Oxidative stress (OS) represents a threat to the chemical integrity of biomolecules including lipids, proteins, and DNA. The associated molecular damage frequently results in serious health issues, which justifies our concern about this phenomenon. In addition to enzymatic defense mechanisms, there are compounds (usually referred to as antioxidants) that offer chemical protection against oxidative events. Among them, melatonin and its metabolites constitute a particularly efficient chemical family. They offer protection against OS as individual chemical entities through a wide variety of mechanisms including electron transfer, hydrogen transfer, radical adduct formation, and metal chelation, and by repairing biological targets. In fact, many of them including melatonin can be classified as multipurpose antioxidants. However, what seems to be unique to the melatonin's family is their collective effects. Because the members of this family are metabolically related, most of them are expected to be present in living organisms wherever melatonin is produced. Therefore, the protection exerted by melatonin against OS may be viewed as a result of the combined antioxidant effects of the parent molecule and its metabolites. Melatonin's family is rather exceptional in this regard, offering versatile and collective antioxidant protection against OS. It certainly seems that melatonin is one of the best nature's defenses against oxidative damage.

Modulation of bone morphogenetic protein activity by melatonin in ovarian steroidogenesis

BACKGROUND

Melatonin regulates circadian and seasonal rhythms and the activities of hormones and cytokines that are expressed in various tissues, including the ovary, in which melatonin receptors are expressed. In the ovary, follicular growth occurs as a result of complex interactions between pituitary gonadotropins and autocrine and paracrine factors, including bone morphogenetic proteins (BMPs) that are expressed in the ovary.

METHODS

The effects of melatonin and BMPs on steroidogenesis were examined by using the primary cultures of rat granulosa cells.

MAIN FINDINGS RESULTS

It was shown that melatonin has antagonistic effects on BMP-6 actions in the granulosa cells, suggesting that melatonin is likely to contribute to balancing the biological activity of endogenous BMPs that maintain progesterone production and luteinization in the growing follicles. Similar interactions between melatonin and BMP-smad signaling also were shown in the mechanism of controlling ovarian steroidogenesis by other ligands.

CONCLUSION

A new role of melatonin in the regulation of endocrine homeostasis in relation to BMP activity is introduced in this review.

RNAi-mediated knockdown of MTNR1B without disrupting the effects of melatonin on apoptosis and cell cycle in bovine granulose cells

Melatonin is well known as a powerful free radical scavenger and exhibits the ability to prevent cell apoptosis. In the present study, we investigated the role of melatonin and its receptor MTNR1B in regulating the function of bovine granulosa cells (GCs) and hypothesized the involvement of MTNR1B in mediating the effect of melatonin on GCs. Our results showed that MTNR1B knockdown significantly promoted GCs apoptosis but did not affect the cell cycle. These results were further verified by increasing the expression of pro-apoptosis genes (BAX and CASP3), decreasing expression of the anti-apoptosis genes (BCL2 and BCL-XL) and anti-oxidant genes (SOD1 and GPX4) without affecting cell cycle factors (CCND1, CCNE1 and CDKN1A) and TP53. In addition, MTNR1B knockdown did not disrupt the effects of melatonin in suppressing the GCs apoptosis or blocking the cell cycle. Moreover, MTNR1B knockdown did not affect the role of melatonin in increasing BCL2, BCL-XL, and CDKN1A expression, or decreasing BAX, CASP3, TP53, CCND1 and CCNE1 expression. The expression of MTNR1A was upregulated after MTNR1B knockdown, and melatonin promoted MTNR1A expression with or without MTNR1B knockdown. However, despite melatonin supplementation, the expression of SOD1 and GPX4 was still suppressed after MTNR1B knockdown. In conclusion, these findings indicate that melatonin and MTNR1B are involved in BCL2 family and CASP3-dependent apoptotic pathways in bovine GCs. MTNR1A and MTNR1B may coordinate the work of medicating the appropriate melatonin responses to GCs.