Melatonin reduces LH, 17 beta-estradiol and induces differential regulation of sex steroid receptors in reproductive tissues during rat ovulation

Mechanisms of probiotic modulation of ovarian sex hormone production and metabolism: a review

Sex hormones play a pivotal role in the growth and development of the skeletal, neurological, and reproductive systems. In women, the dysregulation of sex hormones can result in various health complications such as acne, hirsutism, and irregular menstruation. One of the most prevalent diseases associated with excess androgens is polycystic ovary syndrome with a hyperandrogenic phenotype. Probiotics have shown the potential to enhance the secretion of ovarian sex hormones. However, the underlying mechanism of action remains unclear. Furthermore, comprehensive reviews detailing how probiotics modulate ovarian sex hormones are scarce. This review seeks to shed light on the potential mechanisms through which probiotics influence the production of ovarian sex hormones. The role of probiotics across various biological axes, including the gut-ovarian, gut-brain-ovarian, gut-liver-ovarian, gut-pancreas-ovarian, and gut-fat-ovarian axes, with a focus on the direct impact of probiotics on the ovaries via the gut and their effects on brain gonadotropins is discussed. It is also proposed herein that probiotics can significantly influence the onset, progression, and complications of ovarian sex hormone abnormalities. In addition, this review provides a theoretical basis for the therapeutic application of probiotics in managing sex hormone-related health conditions.

Melatonin promotes progesterone secretion in sheep luteal cells by regulating autophagy via the AMPK/mTOR pathway

The corpus luteum is primarily responsible for the production and secretion of progesterone. Melatonin has been established to regulate autophagy and induce progesterone secretion in luteal cell. However, whether melatonin affects progesterone secretion by interfering with autophagy is yet to be reported. In the present study, the expression levels of melatonin receptors (MT1 and MT2), autophagy-related protein Beclin1 (Bec1), microtubule-associated protein light chain 3 B (LC3B), progesterone and steroidogenic acute regulatory protein (StAR), and cytochrome P450scc (CYP11A1) were analyzed in the corpus luteum of sheep at different stages (early, middle, and late); specifically, enzyme-linked immunosorbent assays, immunohistochemical staining, and western blotting were utilized for this expression analysis. In addition, to determine whether melatonin regulated progesterone secretion via the regulation of autophagy, luteal cells were cultured before being exposed to different concentrations of melatonin (0.01-100 nM) and the autophagy inhibitor chloroquine (50 μM). Next, luteal cells were treated with the melatonin receptor inhibitors 4-phenyl-2-propionamidotetralin (1 μM) and luzindole (1 μM) before detecting Bec1, LC3B2, AMPK/mTOR, and progesterone secretion levels to ascertain whether the effect of melatonin on autophagy and progesterone secretion is mediated by its corresponding receptors in luteal cells. Finally, to determine the significance of the AMPK/mTOR pathway in this process, an AMPK inhibitor, Compound C (10 μM), was added to luteal cells. Overall, the highest expression of melatonin receptors, autophagy and progesterone secretion was observed in the middle-phase corpus luteum; additionally, melatonin promoted autophagy, at least partially, through its receptor-mediated AMPK/mTOR pathway, which thereby promoting progesterone secretion in luteal cells in vitro. Ultimately, this study is the first to clarify the important role of autophagy in the melatonin-mediated regulation of progesterone secretion in the corpus luteum of sheep; it also lays a foundation for further exploration into the role of melatonin in regulating sheep's ovarian function.

The ROS/SIRT1/STAR axis as a target for melatonin ameliorating atrazine-induced mitochondrial dysfunction and steroid disorders in granulosa cells

The granulosa cells (GCs) of birds are essential for the reproduction and maintenance of populations in nature. Atrazine (ATR) is a potent endocrine disruptor that can interfere with reproductive function in females and Diaminochlorotriazine (DACT) is the primary metabolite of ATR in the organism. Melatonin (MT) is an endogenous hormone with antioxidant properties that plays a crucial role in development of animal germ cells. However, how ATR causes mitochondrial dysfunction, abnormal secretion of steroid hormones, and whether MT prevents ATR-induced female reproductive toxicity remains unclear. Thus, the purpose of this study is to investigate the protective effect of MT against ATR-induced female reproduction. In the present study, the GCs of quail were divided into 6 groups, as follows: C (Serum-free medium), MT (10 µM MT), A250 (250 µM ATR), MA250 (10 µM MT+250 µM ATR), D200 (200 µM DACT) and MD200 (10 µM MT+200 µM DACT), and were cultured for 24 h. The results revealed that ATR prevented GCs proliferation and decreased cell differentiation. ATR caused oxidative damage and mitochondrial dysfunction, leading to disruption of steroid synthesis, which posed a severe risk to GC's function. However, MT supplements reversed these changes. Mechanistically, our study exhibited that the ROS/SIRT1/STAR axis as a target for MT to ameliorate ATR-induced mitochondrial dysfunction and steroid disorders in GCs, which provides new insights into the role of MT in ATR-induced reproductive capacity and species conservation in birds.

Influence of Melatonin Treatment on Emotion, Sleep, and Life Quality in Perimenopausal Women: A Clinical Study

Method

100 healthy perimenopausal women were recruited and randomly assigned to two groups, with 50 subjects in each group. In the control group, placebo was administrated daily for 3 cycles (4 weeks of treatment for 1 cycle and drug withdrawals for 1 week). The study group received 3 mg oral melatonin treatment daily in the same period of time. All subjects completed the study. We compared the uterine volume, endometrial thickness, LH (luteinizing hormone), FSH (follicle generating hormone), E2 (estradiol), and melatonin levels during daytime between the two groups before and after the study. Moreover, perimenopause syndrome, sleep, mood, and QoL were analyzed at the baseline and 3 cycles by the questionnaires of the Kupperman index, the Pittsburgh sleep quality index (PSQI), the Hamilton anxiety scale (HAMA), and the Hamilton depression scale (HAMD), as well as menopausal QoL (MENQOL), respectively. Any adverse reactions experienced by the subjects were also compared in the study. Finally, 91 participants (92%) completed the whole study, 47 and 44 in the study and control groups, respectively, and their data were considered in subsequent analyses.

Results

After therapy, the two groups were similar in the uterine volume and endometrial thickness. In contrast to the control group, the study group showed notably decreased LH and FSH levels. No notable difference was discovered in E2 and melatonin levels between the two groups in the study. Moreover, the study group exhibited a significantly lower score in the Kupperman index, PSQI, HAMA, HAMD, and MENQOL scale than the control group. Moreover, the two groups had no notable difference in adverse reactions.

Conclusion

Melatonin was a useful treatment to relieve climacteric symptoms and improve sleep, mood, and life quality in perimenopausal women without obvious adverse reactions.

Gut microbiome and reproductive endocrine diseases: a Mendelian randomization study

Background

Observation studies have confirmed the association between the gut microbiome and reproductive endocrine diseases (REDs), namely, polycystic ovary syndrome (PCOS), endometriosis, and female infertility. However, their association has never been confirmed by a two-sample Mendelian randomization (MR) analysis.

Methods

We conducted a two-sample MR analysis to evaluate the relationship between the gut microbiome and the three aforementioned REDs. In order to get more comprehensive results, two different thresholds were adopted to select instrumental variables (IVs): one was a locus-wide significance threshold (P <1.0×10-5) and the other was a genome-wide significance level (P< 5×10-8). Summary-level statistics for the gut microbiome and REDs were collected from public databases. Inverse-variance weighted (IVW) was the main method used to estimate causality, and sensitivity analyses were conducted to validate the MR results.

Results

At the locus-wide significance level, we identified that the genera Streptococcus (OR=1.52, 95%CI: 1.13-2.06, P=0.006) and RuminococcaceaeUCG005 (OR=1.39, 95%CI: 1.04-1.86, P=0.028) were associated with a high risk of PCOS, while Sellimonas (OR= 0.69, 95%CI: 0.58-0.83, P=0.0001) and RuminococcaceaeUCG011(OR=0.76, 95%CI: 0.60-0.95, P=0.017) were linked to a low PCOS risk. The genus Coprococcus2 (OR=1.20, 95%CI: 1.01-1.43, P=0.039) was correlated with an increased risk of female infertility, while Ruminococcus torques (OR=0.69, 95%CI: 0.54-0.88, P=0.002) were negatively associated with the risk of female infertility. The genera Olsenella (OR= 1.11, 95%CI: 1.01-1.22, P=0.036), Anaerotruncus (OR= 1.25, 95%CI: 1.03-1.53, P=0.025), and Oscillospira (OR= 1.21, 95%CI: 1.01-1.46, P=0.035) were linked to a high risk of endometriosis. However, the results showed that the gut microbiome did not possess a causal link with REDs risk based on the genome-wide significance level. Sensitivity analyses further confirmed the robustness of the MR results.

Conclusion

Our study provides evidence that gut microbiome is closely related with REDs. Subsequent studies should be conducted to promote microbiome-orientated therapeutic strategies for managing REDs.

Clock 3111 T/C and Period3 VNTR gene polymorphisms and proteins, and melatonin levels in women with infertility

PURPOSE

One of the causes of infertility is circadian rhythm disorders. This study aimed to investigate Clock 3111 T/C and Period3 VNTR (variable number tandem repeat) gene polymorphisms and these gene proteins, some biochemical parameters, and circadian rhythm hormones in infertile women.

METHODS

Thirty-five infertile women and thirty-one healthy fertile women were included. Blood samples were taken in the mid-luteal phase. DNAs obtained from peripheral blood were analyzed using polymerase chain reaction-restriction fragment length polymorphism methods. Follicle-stimulating hormone, LH (luteinizing hormone), estradiol, prolactin, free triiodothyronine, fT4 (free thyroxine), thyroid-stimulating hormone, testosterone, cortisol, progesterone, prolactin, ferritin, vitamin B12, and folate levels in serum samples were determined by the electrochemiluminescence immunoassay method. Melatonin, Clock, and Period3 protein levels were determined with ELISA kits.

RESULTS

There was a significant difference in the frequency of Period3 DD (Per34/4) genotype between the groups. The Clock protein level of the infertile group was higher than the fertile group. Clock protein levels of the fertile group were positively correlated with estradiol levels and negatively correlated with LH, prolactin, and fT4 levels. PER3 protein levels of the infertile group were negatively correlated with LH levels. Melatonin levels of the fertile group were positively correlated with progesterone levels and negatively correlated with cortisol levels. Melatonin levels of the infertile group were positively correlated with LH levels and negatively correlated with cortisol levels.

CONCLUSION

Per34/4 genotype may be an independent risk factor in infertile women. Different correlation results found in fertile and infertile women can form the basis for future studies.

Therapeutic effects of melatonin on endometriosis, targeting molecular pathways: Current knowledge and future perspective

Endometriosis, the very serious disease in women creates a huge financial burden worldwide, which is comparable to diabetes mellitus. In addition to the typical pelvic pain, endometriosis is related to low life quality and decreased work efficiency; clinical consequences include mood complaints, metabolic impairments, inflammation, immunologic problems, and elevated malignancy risks. Several risk factors are correlated with endometriosis including elevated oxidative and nitrosative stress, long-lasting inflammation, raised immune tolerance, as well as autoimmunity. Melatonin is a natural molecule present throughout both the plant and animal kingdoms. It has numerous functions as an antioxidant and anti-inflammatory agent. Due to the anti-proliferative, antioxidant, anti-inflammatory, and anti-invasive features of melatonin, it performances as a beneficial agent to limit endometriosis; this involves several pathways including antiestrogenic, antioxidant, anti-inflammatory, and anti-apoptosis effects, as well as reducing the growth of E2-induced endometriotic tissue. Moreover, melatonin can favor sleep quality and decrease the unwanted signs in the patients. However, most of the data on melatonin accured from experimental works and additional clinical trials are needed. This review summarizes what is currently known regarding the influence of melatonin on endometriosis. AVAILABILITY OF DATA AND MATERIAL: Not applicable.

Melatonin in Endometriosis: Mechanistic Understanding and Clinical Insight

Endometriosis is defined as the development of endometrial glands and stroma outside the uterine cavity. Pathophysiology of this disease includes abnormal hormone profiles, cell survival, migration, invasion, angiogenesis, oxidative stress, immunology, and inflammation. Melatonin is a neuroendocrine hormone that is synthesized and released primarily at night from the mammalian pineal gland. Increasing evidence has revealed that melatonin can be synthesized and secreted from multiple extra-pineal tissues where it regulates immune response, inflammation, and angiogenesis locally. Melatonin receptors are expressed in the uterus, and the therapeutic effects of melatonin on endometriosis and other reproductive disorders have been reported. In this review, key information related to the metabolism of melatonin and its biological effects is summarized. Furthermore, the latest in vitro and in vivo findings are highlighted to evaluate the pleiotropic functions of melatonin, as well as to summarize its physiological and pathological effects and treatment potential in endometriosis. Moreover, the pharmacological and therapeutic benefits derived from the administration of exogenous melatonin on reproductive system-related disease are discussed to support the potential of melatonin supplements toward the development of endometriosis. More clinical trials are needed to confirm its therapeutic effects and safety.

The Crosstalk between Melatonin and Sex Steroid Hormones

Melatonin, an indolamine mainly released from the pineal gland, is associated with many biological functions, namely, the modulation of circadian and seasonal rhythms, sleep inducer, regulator of energy metabolism, antioxidant, and anticarcinogenic. Although several pieces of evidence also recognize the influence of melatonin in the reproductive physiology, the crosstalk between melatonin and sex hormones is not clear. Here, we review the effects of sex differences in the circulating levels of melatonin and update the current knowledge on the link between sex hormones and melatonin. Furthermore, we explore the effects of melatonin on gonadal steroidogenesis and hormonal control in females. The literature review shows that despite the strong evidence that sex differences impact on the circadian profiles of melatonin, reports are still considerably ambiguous, and these differences may arise from several factors, like the use of contraceptive pills, hormonal status, and sleep deprivation. Furthermore, there has been an inconclusive debate about the characteristics of the reciprocal relationship between melatonin and reproductive hormones. In this regard, there is evidence for the role of melatonin in gonadal steroidogenesis brought about by research that shows that melatonin affects multiple transduction pathways that modulate Sertoli cell physiology and consequently spermatogenesis, and also estrogen and progesterone production. From the outcome of our research, it is possible to conclude that understanding the correlation between melatonin and reproductive hormones is crucial for the correction of several complications occurring during pregnancy, like preeclampsia, and for the control of climacteric symptoms.

Photoperiodic modulation of ovarian metabolic, survival, proliferation and gap junction markers in adult golden hamster, Mesocricetus auratus

Female reproductive physiology is greatly dependent on tight regulation of metabolic and survival factors. Photoperiod regulates female reproductive rhythms but very less information exists explaining whether photoperiod could modulate thyroid hormone homeostasis, metabolic/energy parameters along with survival, proliferation and gap junction proteins in the ovary of a long-day breeder, Mesocricetus auratus. Adult female hamsters were exposed to different photoperiodic regimes i.e., critical photoperiod (CP; 12.5L:11.5D), short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. LP upregulated thyroidal and gonadal activity as apparent by histoarchitecture, thyroid hormone profile [triiodothyronine (T3), thyroxin (T4) and thyroid stimulating hormone (TSH)], luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) levels when compared with SP exposed hamsters. Further, LP increased thyroid hormone receptor-α/deiodinase-2 (TRα/Dio-2), estrogen receptor-α (ERα)/aromatase and insulin receptor/glucose transporter-4 (IR/GLUT-4) expressions in ovary. Interestingly, ovarian sirtuin-1 (SIRT-1) expression was also upregulated under LP condition along with cell proliferation (proliferating cell nuclear antigen or PCNA), survival (B cell lymphoma-2 or Bcl-2) and gap junction (connexin-43) markers when compared to SP exposed hamsters. We also noted elevated levels of circulatory leptin, insulin along with melatonin and its receptor (MT-1) in ovary under SP condition. Thus, we suggest that photoperiod plays a vital role in regulation of thyroid and reproductive hormone homeostasis along with key metabolic and survival markers in the ovary of adult golden hamsters, M. auratus providing further insight into the regulation of female reproductive seasonality in a long-day breeder.

Melatonin is involved in the modulation of the hypothalamic and pituitary activity in the South American plains vizcacha, Lagostomus maximus

Melatonin, the key messenger of photoperiodic information, is synthesized in the pineal gland by arylalkylamine N-acetyltransferase enzyme (AANAT). It binds to specific receptors MT₁ and MT₂ located in the hypothalamus and pituitary gland. Melatonin can modulate the reproductive axis affecting the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). The South American plains vizcacha, Lagostomus maximus, shows natural poliovulation of up to 800 oocytes per estrous cycle, a 154-day long pregnancy, and reactivation of the reproductive axis at mid-gestation with pre-ovulatory follicular recruitment, presence of active corpora lutea, and variations of the endocrine status. Here we analyzed the involvement of melatonin in the modulation of the hypothalamic and pituitary gland physiology of vizcacha thorough several approaches, including histological localization of melatoninergic system components, assessment of melatoninergic components expression throughout the reproductive cycle, and evaluation of the effect of melatonin on hypothalamic and pituitary activities during the follicular and luteal phases of the estrous cycle. AANAT and melatonin receptors were localized in the pineal gland and preoptic area of the hypothalamus. Increase in pineal AANAT and serum melatonin expression was observed as pregnancy progressed, with the lowest hypothalamic MT₁ and MT₂ levels at mid-pregnancy. Pulsatility assays demonstrated that melatonin induces GnRH and LH secretion at luteal phase. The melatoninergic system effects on hypothalamic and pituitary gland hormones secretion during pregnancy pinpoint to melatonin as a potential key factor underlying the reactivation of the reproductive axis activity at mid-gestation.

Uterine anomalies in cell proliferation, energy homeostasis and oxidative stress in PCOS hamsters, M. auratus: Therapeutic potentials of melatonin

AIMS

Polycystic ovarian syndrome (PCOS) is a reproductive, endocrine and metabolic disorder. Less is known about the mechanism of its effect on uterine function and therapeutic potential of melatonin. Our aim was to evaluate uterine dysfunction(s) in letrozole induced PCOS and its possible rectification by melatonin.

MAIN METHODS

Adult female golden hamsters were divided into groups of Control (C), Melatonin (M; 1 mg/kg b.w.), Letrozole (L; 3 mg/kg b.w.) and combination of Letrozole+Melatonin (L + M; 3 mg/kg b.w. + 1 mg/kg b.w.) which were treated for 40 days. Analysis of serum testosterone/estradiol/progesterone/leptin/insulin, uterine histomorphometry, immunohistochemistry for proliferation cell nuclear antigen (PCNA), homeostatic assessment model of insulin resistance (HOMA-IR), western blotting for PCNA, androgen receptor (AR), insulin receptor (InsR), glucose tansporter-4 (GLUT-4), nuclear factor-kappa B (NFκB), cyclooxygenase-2 (COX-2) and biochemical analysis of superoxide dismutase (SOD)/catalase/lipid peroxidation (LPO) were done.

KEY FINDINGS

Serum testosterone, leptin and insulin increased while uterine InsR/GLUT-4 expression decreased in L group indicating metabolic abnormalities. Endometrial hyperplasia, increased expression of PCNA and AR indicated abnormal proliferation in L compared to C. Increased uterine oxidative load (SOD/catalase/LPO) and inflammatory markers NFκB/COX-2 expression in L was responsible for high tissue oxidative stress and inflammation. M administration normalized all the above parameters suggesting its ameliorative effect in L + M group.

SIGNIFICANCE

We report PCOS induced uterine dysfunction in Mesocricetus auratus for the first time. M administration restores uterine functions modulating cellular dynamicity, metabolic status, decreased oxidative and inflammatory load in PCOS hamsters. Therefore, we suggest the therapeutic potential of M against PCOS led uterine abnormalities to restore female fertility.

Nandrolone decanoate causes uterine injury by changing hormone levels and sex steroid receptors in a dose- and time-dependent manner

Different doses of nandrolone decanoate (ND) were used to investigate the expression of uterine sex steroid receptors (AR, ER-α, and ER-β) and the levels of serum sex hormones after treatment and recovery periods in adult rats. ND doses of 1.87, 3.75, 7.5, or 15 mg/kg b.w. or mineral oil (control group) were injected subcutaneously for 15 days, and the experimental groups were divided into three periods of evaluation: (a) ND treatment for 15 days, (b) ND treatment followed by 30-day-recovery and (c) ND treatment followed by 60-day-recovery. Estrous cycle was monitored daily. At the end of each experimental period, rats were euthanized for the collection of serum samples and uterine tissues. All animals showed persistent diestrus and only the highest ND dose was capable of inducing persistent diestrus until 60-day-recovery. Immunoexpression of uterine sex steroid receptors varied in a time-dependent manner. While AR expression was increase after treatment period, ER-α and ER-β expressions decreased after 60- and 30-day-recovery, respectively. ND also increased the serum levels of testosterone, 17β-estradiol, and dihydrotestosterone, especially at the highest doses of 7.5 and 15 mg ND/kg until 30 days of recovery. The levels of progesterone were significantly reduced in all ND-treated animals. No significant difference was observed in the levels of follicle-stimulating hormone, whereas the levels of luteinizing hormone varied according to specific dose and period. We conclude that uterine sex steroid receptors and sex hormones are affected by ND administration and these alterations can be only restored following lower doses and long recovery periods.

Ovulation mitigates fatty liver associated with reproductive suppression and oxidative stress in Damaraland mole-rats (Fukomys damarensis)

Oxidative damage is often linked to reproduction; however, reproducing female Damaraland mole-rats (Fukomys damarensis) exhibit a reduction in oxidative damage relative to their non-reproductive, anovulatory, cohorts. Specifically, liver concentrations of malondialdehyde, a biomarker for lipid peroxidation, are significantly lower in reproducing females. We examined liver histology in reproductive, anovulatory and recently ovulating non-reproductive females, demonstrating an accumulation of lipid droplets only in the livers of anovulatory females and no fibrosis, cell death or inflammatory infiltrates in any group. Our observations suggest that anovulatory females experience a form of non-alcoholic fatty liver disease, which is reversed once they commence ovulation. We propose hormonal interactions that may underlie our observations.

Is Melatonin the Cornucopia of the 21st Century?

Melatonin, an indoleamine hormone produced and secreted at night by pinealocytes and extra-pineal cells, plays an important role in timing circadian rhythms (24-h internal clock) and regulating the sleep/wake cycle in humans. However, in recent years melatonin has gained much attention mainly because of its demonstrated powerful lipophilic antioxidant and free radical scavenging action. Melatonin has been proven to be twice as active as vitamin E, believed to be the most effective lipophilic antioxidant. Melatonin-induced signal transduction through melatonin receptors promotes the expression of antioxidant enzymes as well as inflammation-related genes. Melatonin also exerts an immunomodulatory action through the stimulation of high-affinity receptors expressed in immunocompetent cells. Here, we reviewed the efficacy, safety and side effects of melatonin supplementation in treating oxidative stress- and/or inflammation-related disorders, such as obesity, cardiovascular diseases, immune disorders, infectious diseases, cancer, neurodegenerative diseases, as well as osteoporosis and infertility.

Effects of melatonin on uterine hypertrophy/hyperplasia: A preliminary experimental rat study

Endometrial hyperplasia is a process of endometrial proliferation that results in a thickening of the endometrial tissue. Melatonin might be able to change the pathophysiological process and prognosis into a positive way that might prevent and heal endometrial hyperplasia, which is the first stage of endometrial cancer. For this perspective, we tried to investigate the effect of melatonin on uterine hypertrophy/hyperplasia in an experimental rat model. Forty Wistar-Albino rats were undergone bilateral oophorectomy and randomized into four groups. To create a model of uterine hypertrophy/hyperplasia in all groups, except the control group [C] (n = 10), 4 mg/kg/day estradiol hemihydrate were given for 14 days. The uterine hypertrophy/hyperplasia was evaluated histopathologically in the left uterine horns, then the groups were treated for 14 days as follows; melatonin (10 mg/kg/day/po) [M] (n = 10), melatonin + estradiol hemihydrate (10 mg/kg/day/po and 4 mg/kg/day/po) [M + E] (n = 10), and dark environment [D] (n = 10). Finally, the effects of the melatonin were examined histopathologically in the right uterine horns. An uterine hypertrophy/hyperplasia model was established in all groups compared to the control group (p < 0.05). In the [M] and [M + E] groups, epithelial cell height and luminal epithelial cell height significantly decreased (41μm vs 12μm, p = 0.005; 14μm vs 10μm, p = 0.005, respectively for [M] group) and (32μm vs 14μm, p = 0.012; 17μm vs 10μm, p = 0.017, respectively for [M + E] group). The [D] group exhibited a significant decrease in epithelial cell height (33μm vs 20μm, p = 0.017). With or without estrogen exposure, melatonin-treated and physiologically melatonin-released rats experienced a significant uterine hypertrophy/hyperplasia recovery. Melatonin may have protective effects on endometrial hyperplasia.

Topical Melatonin Improves Gastric Microcirculatory Oxygenation During Hemorrhagic Shock in Dogs but Does Not Alter Barrier Integrity of Caco-2 Monolayers

Systemic administration of melatonin exerts tissue protective effects in the context of hemorrhagic shock. Intravenous application of melatonin prior to hemorrhage improves gastric microcirculatory perfusion and maintains intestinal barrier function in dogs. The aim of the present study was to analyze the effects of a topical mucosal melatonin application on gastric microcirculation during hemorrhagic shock in vivo and on mucosal barrier function in vitro. In a randomized cross-over study, six anesthetized female foxhounds received 3.3 mg melatonin or the vehicle as a bolus to the gastric and oral mucosa during physiological and hemorrhagic (-20% blood volume) conditions. Microcirculation was analyzed with reflectance spectrometry and laser doppler flowmetry. Systemic hemodynamic variables were measured with transpulmonary thermodilution. For analysis of intestinal mucosal barrier function in vitro Caco-2 monolayers were used. The transepithelial electrical resistance (TEER) and the passage of Lucifer Yellow (LY) from the apical to the basolateral compartment of Transwell chambers were measured. Potential barrier protective effects of melatonin against oxidative stress were investigated in the presence of the oxidant H₂O₂. During physiologic conditions topical application of melatonin had no effect on gastric and oral microcirculation in vivo. During hemorrhagic shock, gastric microcirculatory oxygenation (μHbO₂) was decreased from 81 ± 8% to 50 ± 15%. Topical treatment with melatonin led to a significant increase in μHbO₂ to 60 ± 13%. Topical melatonin treatment had no effect on gastric microcirculatory perfusion, oral microcirculation or systemic hemodynamics. Incubation of H₂O₂ stressed Caco-2 monolayers with melatonin did neither influence transepithelial electrical resistance nor LY translocation. Topical treatment of the gastric mucosa with melatonin attenuates the shock induced decrease in microcirculatory oxygenation. As no effects on local microcirculatory and systemic perfusion were recorded, the improved μHbO₂ is most likely caused by a modulation of local oxygen consumption. In vitro melatonin treatment did not improve intestinal barrier integrity in the context of oxidative stress. These results extend the current knowledge on melatonin's protective effects during hemorrhage in vivo. Topical application of melatonin exerts differential effects on local microcirculation compared to systemic pretreatment and might be suitable as an adjunct for resuscitation of hemorrhagic shock.

Higher doses of Melatonin affect ovarian and middle uterine arteries vascular blood flow and induce oestrus earlier in acyclic ewes

The present study aimed to evaluate the effect of a single intramuscular injection of melatonin on response of oestrus, rate of conception, ovarian and uterine blood supply during the non-breeding season. Melatonin powder was dissolved in dimethyl sulfoxide (DMSO) and olive oil and injected in two dose of 25 mg (MEL-1; n = 10) and 50 mg (MEL-2; n = 10) in May. Ten ewes were served as the control (CON). Results showed that oestrous response was higher in the MEL-2 group than in other groups (p < .01). The time to onset of oestrus in both the MEL-1 and MEL-2 groups was significantly shorter, compared with the CON group (p < .01). Pregnancy rates reached 80% and 90% at 45 days of gestation. Doppler indices of the right and left ovarian artery were lower in the melatonin groups than in normal groups (p < .01). Both Doppler indices in uterine arteries were not different among two treatment groups (p > .05), but there was a significant difference when compared with the CON group (p < .01), no difference found between two treatment group in the Doppler velocities of middle uterine arteries (p > .05). In conclusion, the definite changes in the studied parameters showed two novel findings; (a) the increase in melatonin dose results in increasing the blood flow expressed by increased Doppler velocities in fatty tailed ewes, (b) as well as, melatonin can initiate the breeding season regardless of the season earlier by 1-2 months in ewes.

Curcumin and Endometriosis

Endometriosis is one of the main common gynecological disorders, which is characterized by the presence of glands and stroma outside the uterine cavity. Some findings have highlighted the main role of inflammation in endometriosis by acting on proliferation, apoptosis and angiogenesis. Oxidative stress, an imbalance between reactive oxygen species and antioxidants, could have a key role in the initiation and progression of endometriosis by resulting in inflammatory responses in the peritoneal cavity. Nevertheless, the mechanisms underlying this disease are still unclear and therapies are not currently efficient. Curcumin is a major anti-inflammatory agent. Several findings have highlighted the anti-oxidant, anti-inflammatory and anti-angiogenic properties of curcumin. The purpose of this review is to summarize the potential action of curcumin in endometriosis by acting on inflammation, oxidative stress, invasion and adhesion, apoptosis and angiogenesis.

Programming of hepatic lipid metabolism in a rat model of postnatal nicotine exposure - Sex-related differences

Maternal nicotine exposure during lactation induces liver damage in adult male rats. However, the mechanism in males is unknown and females have not been tested. Here, we determined the liver lipid composition and lipogenic enzymes in male and female offspring at two ages in a model of postnatal nicotine exposure. Osmotic minipumps were implanted in lactating Wistar rat dams at postnatal day (PND) 2 to release 6 mg/kg/day of nicotine (NIC group) or saline (CON group) for 14 days. Offspring received a standard diet from weaning until euthanasia at PND120 (1 pup/litter/sex) or PND180 (2 pups/litter/sex). At PND120, NIC males showed lower plasma triglycerides (TG), steatosis degree 1, higher hepatic cholesterol (CHOL) ester, free fatty acids, monoacylglycerol content as well as acetyl-coa carboxylase-1 (ACC-1) and fatty acid synthase (FAS) protein expression in the liver compared to CON males. At this age, NIC females had preserved hepatocytes architecture, higher plasma CHOL, higher CHOL ester and lower total CHOL content in the liver compared to CON females. At PND180, NIC males showed steatosis degrees 1 and 2, higher TG, lower free fatty acids and total CHOL content in the liver and an increase in ACC-1 hepatic protein expression. NIC females had higher plasma TG and CHOL levels, no change in hepatic morphology, lower CHOL ester and free fatty acids in the liver, which also showed higher total ACC-1 and FAS protein expression. Maternal nicotine exposure induces long-term liver dysfunction, with an alteration in hepatic cytoarchitecture that was aggravated with age in males. Concerning females, despite unchanged hepatic cytoarchitecture, lipid metabolism was compromised, which deserves further attention.

Evidence that Melatonin Increases Inhibin Beta-A and Follistatin Gene Expression in Ovaries of Pinealectomized Rats

Melatonin plays an important role in the regulation of ovarian function including oocyte maturation in different mammalian species. Many studies indicate that melatonin has an impact on the ovarian function of a variety of ovarian cells. However, the information on the exact mechanism and involved hormones is low. To evaluate inhibin beta-A (INHBA) and follistatin (FST) expression in the ovaries of pinealectomized rats treated with melatonin, thirty adult female Wistar rats were randomized into three groups of ten animals each: group 1 (GSh), sham-operated controls receiving vehicle; group 2 (GPx), pinealectomized animals receiving vehicle; and group 3 (GPxMe), pinealectomized animals receiving replacement melatonin (1.0 mg/kg body weight. It was assumed that each animal drank 6.5 ± 1.2 ml per night and weighs approximately 300 g.) for 60 consecutive days. The ovaries were collected for mRNA abundance and protein of INHBA and FST by qRT-PCR and immunohistochemical analyses, respectively. Treatment with melatonin resulted in the upregulation of INHBA and FST genes in the ovarian tissue of the melatonin-treated animals (GPxMe), when compared with GPx. These findings were then confirmed by analyzing the expression of protein by immunohistochemical analyses, which revealed higher immunoreactivity of INHBA and FST in GPxMe animals in the follicular cells compared with GSh and GPx rats. Melatonin increases the expression of INHBA and FST in the ovaries of pinealectomized female rats.

The expression of melatonin receptors MT1 and MT2 is regulated by E2 in sheep oviduct

Some of the functions of melatonin in mammals are exerted through its membrane receptors (MRs) and studies have shown that estradiol (E2) might play an important role in regulating the expression of these proteins in female reproductive organs. However, no reports have reported the expression of MRs in the sheep oviduct or whether they are regulated by E2. Thus, herein, we detected the localization of MT1 and MT2 in the sheep oviduct. Moreover, we also investigated the expression pattern of these markers in the ovulating and non-ovulating side of the oviduct in the sheep ampulla and isthmus. Immunohistochemistry analyses revealed that both MT1 and MT2 are mainly expressed on oviduct epithelial cells. Both real-time polymerase chain reaction (qPCR) and western blot analyses showed that MT1 and MT2 genes and proteins are highly expressed on the non-ovulating side of the oviduct ampulla, but not the ovulating side. However, regarding the oviduct isthmus, there were no significant differences between the ovulating and non-ovulating sides. In vitro, 10 ng/ml and 1 µg/ml of E2, as well as 1 µg/ml of E2 combined with 0.1 µg/ml, 1 µg/ml, and 10 µg/ml of ICI182780 (a non-selective estrogenreceptor antagonist), were used to treat oviduct epithelial cells. We found that E2 inhibited the expression of MT1 and MT2 in cultured oviduct cells. Moreover, the inhibitory effect was suppressed by ICI182780. In conclusion, it was demonstrated that MRs are present in the sheep oviduct, and that E2, via the ER pathway, regulates their expression in the oviduct.

Melatonin Promotes Uterine and Placental Health: Potential Molecular Mechanisms

The development of the endometrium is a cyclic event tightly regulated by hormones and growth factors to coordinate the menstrual cycle while promoting a suitable microenvironment for embryo implantation during the “receptivity window”. Many women experience uterine failures that hamper the success of conception, such as endometrium thickness, endometriosis, luteal phase defects, endometrial polyps, adenomyosis, viral infection, and even endometrial cancer; most of these disturbances involve changes in endocrine components or cell damage. The emerging evidence has proven that circadian rhythm deregulation followed by low circulating melatonin is associated with low implantation rates and difficulties to maintain pregnancy. Given that melatonin is a circadian-regulating hormone also involved in the maintenance of uterine homeostasis through regulation of numerous pathways associated with uterine receptivity and gestation, the success of female reproduction may be dependent on the levels and activity of uterine and placental melatonin. Based on the fact that irregular production of maternal and placental melatonin is related to recurrent spontaneous abortion and maternal/fetal disturbances, melatonin replacement may offer an excellent opportunity to restore normal physiological function of the affected tissues. By alleviating oxidative damage in the placenta, melatonin favors nutrient transfer and improves vascular dynamics at the uterine–placental interface. This review focuses on the main in vivo and in vitro functions of melatonin on uterine physiological processes, such as decidualization and implantation, and also on the feto-maternal tissues, and reviews how exogenous melatonin functions from a mechanistic standpoint to preserve the organ health. New insights on the potential signaling pathways whereby melatonin resists preeclampsia and endometriosis are further emphasized in this review.

P-MAPA and IL-12 Differentially Regulate Proteins Associated with Ovarian Cancer Progression: A Proteomic Study

To investigate the potential role of immunotherapies in the cellular and molecular mechanisms associated with ovarian cancer (OC), we applied a comparative proteomic toll using protein identification combined with mass spectrometry. Herein, the effects of the protein aggregate magnesium-ammonium phospholinoleate-palmitoleate anhydride, known as P-MAPA, and the human recombinant interleukin-12 (hrIL-12) were tested alone or in combination in human SKOV-3 cells. The doses and period were defined based on a previous study, which showed that 25 μg/mL P-MAPA and 1 ng/mL IL-12 are sufficient to reduce cell metabolism after 48 h. Indeed, among 2,881 proteins modulated by the treatments, 532 of them were strictly concordant and common. P-MAPA therapy upregulated proteins involved in tight junction, focal adhesion, ribosome constitution, GTP hydrolysis, semaphorin interactions, and expression of SLIT and ROBO, whereas it downregulated ERBB4 signaling, toll-like receptor signaling, regulation of NOTCH 4, and the ubiquitin proteasome pathway. In addition, IL-12 therapy led to upregulation of leukocyte migration, tight junction, and cell signaling, while cell communication, cell metabolism, and Wnt signaling were significantly downregulated in OC cells. A clear majority of proteins that were overexpressed by the combination of P-MAPA with IL-12 are involved in tight junction, focal adhesion, DNA methylation, metabolism of RNA, and ribosomal function; only a small number of downregulated proteins were involved in cell signaling, energy and mitochondrial processes, cell oxidation and senescence, and Wnt signaling. These findings suggest that P-MAPA and IL-12 efficiently regulated important proteins associated with OC progression; these altered proteins may represent potential targets for OC treatment in addition to its immunoadjuvant effects.

Endometriosis Pathoetiology and Pathophysiology: Roles of Vitamin A, Estrogen, Immunity, Adipocytes, Gut Microbiome and Melatonergic Pathway on Mitochondria Regulation

Endometriosis is a common, often painful, condition that has significant implications for a woman’s fertility. Classically, endometriosis has been conceptualized as a local estrogen-mediated uterine condition driven by retrograde menstruation. However, recent work suggests that endometriosis may be a systemic condition modulated, if not driven, by prenatal processes. Although a diverse array of factors have been associated with endometriosis pathophysiology, recent data indicate that the low body mass index and decreased adipogenesis may be indicative of an early developmental etiology with alterations in metabolic function crucial to endometriosis pathoetiology.

The present article reviews the data on the pathoetiology and pathophysiology of endometriosis, suggesting key roles for alterations in mitochondria functioning across a number of cell types and body systems, including the immune system and gut microbiome. These changes are importantly regulated by decreases in vitamin A and its retinoic acid metabolites as well as increases in mitochondria estrogen receptor-beta and the N-acetylserotonin/melatonin ratio across development. This has treatment and future research implications for this still poorly managed condition, as well as for the association of endometriosis with a number of cancers.

Melatonin protects in vitro matured porcine oocytes from toxicity of Aflatoxin B1

Aflatoxin B1 (AFB1) is a major food and feed contaminant that threaten public health. Previous studies indicate that AFB1 exposure disrupted oocyte maturation. However, an effective and feasible method is unavailable for protecting oocytes against toxicity of AFB1. In the present study, using in vitro matured porcine oocytes and parthenogenetic embryos as model, we confirmed that AFB1 exposure during in vitro oocyte maturation (IVM) significantly impaired both nuclear and cytoplasmic maturation in a dose- and time-dependent manner. The different concentrations of melatonin were also tested for their protective effects on oocytes against the AFB1-induced toxicity. Our results showed that supplementation of a relative high concentration of melatonin (10^-3 mol/L) during IVM efficiently reversed the impaired development rate and blastocyst quality, to the levels comparable to those of the control group. Further analysis indicated that melatonin application efficiently alleviated reactive oxygen species accumulation and initiation of apoptosis induced by AFB1 exposure. In addition, disrupted GSH/GPX system, as well as inhibited mitochondrial DNA (mtDNA) replication and mitochondrial biogenesis in AFB1-treated oocytes, can be notably reversed by melatonin application. Furthermore, cumulus cells may be important in mediating the toxicity of AFB1 to oocytes, and the metabolism of AFB1 in cumulus cells can be depressed by melatonin. To the best of our knowledge, this is the first report to confirm that melatonin application can efficiently protect oocytes from AFB1-induced toxicity. Our study provides a promising and practical strategy for alleviating or reversing AFB1-induced female reproductive toxicity in both clinical treatment and domestic reproductive management.

Mitochondrial functions and melatonin: a tour of the reproductive cancers

Cancers of the reproductive organs have a strong association with mitochondrial defects, and a deeper understanding of the role of this organelle in preneoplastic-neoplastic changes is important to determine the appropriate therapeutic intervention. Mitochondria are involved in events during cancer development, including metabolic and oxidative status, acquisition of metastatic potential, resistance to chemotherapy, apoptosis, and others. Because of their origin from melatonin-producing bacteria, mitochondria are speculated to produce melatonin and its derivatives at high levels; in addition, exogenously administered melatonin accumulates in the mitochondria against a concentration gradient. Melatonin is transported into tumor cell by GLUT/SLC2A and/or by the PEPT1/2 transporters, and plays beneficial roles in mitochondrial homeostasis, such as influencing oxidative phosphorylation and electron flux, ATP synthesis, bioenergetics, calcium influx, and mitochondrial permeability transition pore. Moreover, melatonin promotes mitochondrial homeostasis by regulating nuclear DNA and mtDNA transcriptional activities. This review focuses on the main functions of melatonin on mitochondrial processes, and reviews from a mechanistic standpoint, how mitochondrial crosstalk evolved in ovarian, endometrial, cervical, breast, and prostate cancers relative to melatonin's known actions. We put emphasis on signaling pathways whereby melatonin interferes within cancer-cell mitochondria after its administration. Depending on subtype and intratumor metabolic heterogeneity, melatonin seems to be helpful in promoting apoptosis, anti-proliferation, pro-oxidation, metabolic shifting, inhibiting neovasculogenesis and controlling inflammation, and restoration of chemosensitivity. This results in attenuation of development, progression, and metastatic potential of reproductive cancers, in addition to lowering the risk of recurrence and improving the life quality of patients.

Profile of melatonin and its receptors and synthesizing enzymes in cumulus-oocyte complexes of the developing sheep antral follicle-a potential estradiol-mediated mechanism

BACKGROUND

Melatonin is an amine hormone that plays an important role in regulating mammalian reproduction. This study aimed to investigate the expression pattern of melatonin synthesis enzymes AANAT and HIOMT and melatonin receptors MT1 and MT2 in sheep cumulus-oocyte complexes (COCs) as well as the change of melatonin level in follicular fluid (FF) during antral follicle development. In this research, we also study the effect of β-estradiol (E2) on MT1 and MT2 expression as well as melatonin synthesis in COCs so as to lay the foundation for further exploration of the regulation mechanism of melatonin synthesis in the ovary.

METHODS

COCs and FF were collected from different size (large follicles (diameter ≥ 5 mm), medium follicles (diameter 2-5 mm), and small follicles (diameter ≤ 2 mm)) of antral follicles in sheep ovaries. To assess whether E2 regulates melatonin synthase and its receptors expression in sheep COCs and whether it is mediated through estrogen receptor (ER) pathway. The collected COCs were cultured in vitro for 24 h and then treat with 1 μM E2 and/or 1 μM ICI182780 (non-selective ER antagonist). The expression of AANAT, HIOMT, MT1 and MT2 mRNA and protein were determined by qRT-PCR and western blot. The melatonin level was determined by ELISA.

RESULTS

The expression of AANAT, HIOMT, MT1 and MT2 were significantly higher expression in the COCs of small follicles than in those of large follicles (P < 0.05). However, the melatonin level was significantly higher in large follicle FF than in small follicle FF (P < 0.05). Further, the expression of AANAT, HIOMT, MT1, and MT2 and melatonin production were decreased by E2 treatment (P < 0.05), but when ICI182780 was added, the expression of AANAT, HIOMT, MT1, and MT2 and melatonin production recovered (P < 0.05).

CONCLUSIONS

We suggest that sheep COCs can synthesize melatonin, but this ability is decreased with increasing follicle diameter. Furthermore, E2 play an important role in regulated the expression of MT1 and MT2 as well as melatonin synthesis in sheep COCs through the ER pathway.

Role of melatonin on embryo viability in sheep

Melatonin is a natural hormone synthesised in the pineal gland, the activity of which is regulated by day-night perception and dictates seasonal rhythms in reproduction in ovine species. Exogenous melatonin, administered via subcutaneous implants, is used to prolong the breeding season of ewes and can increase the proportion of pregnant ewes (fertility rate) and litter size. The increased proportion of ewes that become pregnant and the number of lambs born per lambing among melatonin-treated sheep may be caused by increased embryo survival, through enhanced luteal function, reduced antiluteolytic mechanisms, or improved embryo quality. This review focuses on the effects of melatonin on embryo viability and summarises the processes by which this hormone affects the ovary, follicle, oocyte, corpus luteum and embryo. Moreover, the effects of melatonin on the mechanisms of invivo maternal recognition of pregnancy in sheep and the protective action that it appears to have on the invitro procedures that are used to obtain healthy embryos are reviewed.

Adverse events associated with oral administration of melatonin: A critical systematic review of clinical evidence

While melatonin was once thought of simply as a sleep-inducing hormone, recent research has resulted in development of a deeper understanding of the complex physiological activity of melatonin in the human body. Along with this understanding has come widespread, increasing use of melatonin supplementation, extending beyond its traditional use as a sleep aid into novel fields of application. This increased use often involves off-label and self-prescription, escalating the importance of safety data. In order to examine the current knowledge relating to safety of the exogenous neurohormone, we conducted a comprehensive, critical systematic review of clinical evidence. We examined controlled studies of oral melatonin supplementation in humans when they presented any statistical analysis of adverse events. Of the fifty articles identified, twenty-six found no statistically significant adverse events, while twenty-four articles reported on at least one statistically significant adverse event. Adverse events were generally minor, short-lived and easily managed, with the most commonly reported adverse events relating to fatigue, mood, or psychomotor and neurocognitive performance. A few studies noted adverse events relating to endocrine (e.g. reproductive parameters, glucose metabolism) and cardiovascular (e.g. blood pressure, heart rate) function, which appear to be influenced by dosage, dose timing and potential interactions with antihypertensive drugs. Oral melatonin supplementation in humans has a generally favourable safety profile with some exceptions. Most adverse effects can likely be easily avoided or managed by dosing in accordance with natural circadian rhythms. Further research is required to explore the potential for melatonin to interact with endogenous hormones and pharmaceuticals.

From Implantation to Birth: Insight into Molecular Melatonin Functions

Melatonin is a lipophilic hormone synthesized and secreted mainly in the pineal gland, acting as a neuroendocrine transducer of photoperiodic information during the night. In addition to this activity, melatonin has shown an antioxidant function and a key role as regulator of physiological processes related to human reproduction. Melatonin is involved in the normal outcome of pregnancy, beginning with the oocyte quality, continuing with embryo implantation, and finishing with fetal development and parturition. Melatonin has been shown to act directly on several reproductive events, including folliculogenesis, oocyte maturation, and corpus luteum (CL) formation. The molecular mechanism of action has been investigated through several studies which provide solid evidence on the connections between maternal melatonin secretion and embryonic and fetal development. Melatonin administration, reducing oxidative stress and directly acting on its membrane receptors, melatonin thyroid hormone receptors (MT1 and MT2), displays effects on the earliest phases of pregnancy and during the whole gestational period. In addition, considering the reported positive effects on the outcomes of compromised pregnancies, melatonin supplementation should be considered as an important tool for supporting fetal development, opening new opportunities for the management of several reproductive and gestational pathologies.

Histopathological changes in androgenized ovaries are recovered by melatonin treatment

Nandrolone decanoate (ND) is a synthetic steroid, which promotes adverse effects on the ovarian tissue, and melatonin (MLT) exhibits a number of beneficial properties in the reproductive system. This study evaluated the general features of the ovarian tissue and the immunoexpression of sex steroid receptors in ND-treated rats that were submitted to short-term melatonin treatment. Adult rats received mineral oil (control group) and ND at doses of 7.5 mg/kg for 15 days (ND-treated group). The treatment with MLT (10mg/kg for 7 days) was given alone, before or in combination with ND. All ND-treated animals showed persistent dioestrus. In the androgenized groups that received MLT, ovarian morphology and size, and the number/area of corpora lutea were recovered. The number of healthy and atretic follicles was recovered when MLT was administered prior to ND; this was similar to the ovaries of control and MLT groups. There was a decrease in estrogen receptors immunostaining in the follicles of androgenized rats that were treated with MLT, and pretreatment with MLT reduced the expression of androgen receptor in atretic follicles and corpora lutea, when compared with ND-treated group. We conclude that MLT treatment recovered the histopathological aspects of the androgenized ovaries, and MLT pretreatment was the most effective.

Research progress on the role of melatonin and its receptors in animal reproduction: A comprehensive review

Melatonin and its receptors play a crucial role in the regulation of the animal reproductive process, primarily in follicular development. However, the role that melatonin performs in regulating hormones related with reproduction remains unclear. Melatonin and its receptors are present both in female and male animals' organs, such as ovaries, heart, brain and liver. Melatonin regulates ovarian actions and is a key mediator of reproductive actions. Melatonin has numerous effects on animal reproduction, such as protection of gametes and embryos, response to clock genes, immune-neuroendocrine, reconciliation of seasonal variations in immune function, and silence or blockage of genes. The growth ratio of reproductive illnesses in animals has raised a remarkable concern for the government, animal caretakers and farm managers. In order to resolve this challenging issue, it is very necessary to conduct state-of-the-art research on melatonin and its receptors because melatonin has considerable physiognomies. This review article presents a current contemporary research conducted by numerous researchers from the entire world on the role of melatonin and its receptors in animal reproduction, from the year 1985 to the year 2017. Furthermore, this review shows scientific research challenges related to melatonin receptors and their explanations based on the findings of 172 numerous research articles, and also represents significant proficiencies of melatonin in order to show enthusiastic study direction for animal reproduction researchers.

Pleiotropic roles of melatonin in endometriosis, recurrent spontaneous abortion, and polycystic ovary syndrome

Melatonin is a neurohormone synthesized from the aromatic amino acid tryptophan mainly by the pineal gland of mammals. Melatonin acts as a broad-spectrum antioxidant, powerful free radical scavenger, anti-inflammatory agent, anticarcinogenic factor, sleep inducer and regulator of the circadian rhythm, and potential immunoregulator. Melatonin and reproductive system are interrelated under both physiological and pathological conditions. Oxidative stress, inflammation, and immune dysregulation are associated with the pathogenesis of the female reproductive system which causes endometriosis (EMS), recurrent spontaneous abortion (RSA), and polycystic ovary syndrome (PCOS). Accumulating studies have indicated that melatonin plays pleiotropic and essential roles in these obstetrical and gynecological disorders and would be a candidate therapeutic drug to regulate inflammation and immune function and protect special cells or organs. Here, we systematically review the pleiotropic roles of melatonin in EMS, RSA, and PCOS to explore its pathological implications and treatment potential.

Knockdown of melatonin receptor 1 and induction of follicle-stimulating hormone on the regulation of mouse granulosa cell function

Melatonin receptor 1 (MT1) performs a critical role in the regulation of the animal reproductive system, particularly in follicular growth, and has a considerable effect on reproductive performance. However, the role that MT1 plays in regulating hormones associated with reproduction remains unclear. This study was designed to examine the physiological role of constitutive MT1 silencing and follicle stimulating hormone (FSH) treatment in reproduction, making use of mouse granulosa cells (mGCs) as a model. To understand the constitutive role of MT1 in ovarian physiology, the RNAi-Ready pSIREN-RETROQ-ZsGreen Vector mediated recombinant pshRNA was used to silence MT1 gene expression. Furthermore, we observed that the expression of MT1 was successfully inhibited both at the protein and mRNA levels (P<0.001). We demonstrated that RNAi-B-mediated MT1 down-regulation significantly promoted apoptosis (P<0.001), inhibited proliferation, and regulated the cell cycle at the S-phase; conversely, FSH treatment partially aided the apoptotic effect and improved proliferation but showed a significant effect at the S-phase of the cell cycle. Transitory knockdown of MT1 proved essential in the function of mGCs, as it significantly decreased cyclic adenosine monophospahte (cAMP) level and increased cell apoptosis. Following knockdown of MT1, the expression of Bax was significantly up-regulated (P<0.001), but Bcl-2 was slightly down-regulated, both at the transcriptional and at translational levels. Moreover, the silencing of MT1 and its constitutive effect on FSH significantly promoted an increase in estradiol (P<0.001) and slightly decreased the concentration of progesterone. Together, our data indicates that MT1 suppression leads to interference in the normal physiological function of the ovary by enhancing follicular apoptosis, inhibiting proliferation, and influencing hormonal signaling, whereas constitutive FSH treatment counteracted the negative down-regulatory effects of MT1 on mGCs.

Effects of melatonin administration on embryo implantation and offspring growth in mice under different schedules of photoperiodic exposure

BACKGROUND

Embryo implantation is crucial for animal reproduction. Unsuccessful embryo implantation leads to pregnancy failure, especially in human-assisted conception. Environmental factors have a profound impact on embryo implantation. Because people are being exposed to more light at night, the influence of long-term light exposure on embryo implantation should be explored.

METHODS

The effects of long photoperiodic exposure and melatonin on embryo implantation and offspring growth were examined. Long photoperiodic exposure (18:6 h light:dark) was selected to resemble light pollution. Melatonin (10^-2, 10^-3, 10^-4, 10^-5 M) was added to the drinking water of mice starting at Day 1 (vaginal plugs) until delivery.

RESULTS

Melatonin treatment (10^-4,10^-5 M) significantly increased litter sizes compared to untreated controls (12.9 ± 0.40 and 12.2 ± 1.01 vs. 11.5 ± 0.43; P < 0.05). The most effective concentration of melatonin (10^-4 M) was selected for further investigation. No remarkable differences were found between melatonin-treated mice and controls in terms of the pups' birth weights, weaning survival rates, and weaning weights. Long photoperiodic exposure significantly reduced the number of implantation sites in treated mice compared to controls (light/dark, 12/12 h), and melatonin rescued this negative effect. Mechanistic studies revealed that melatonin enhanced the serum 17β-estradiol (E₂) levels in the pregnant mice and upregulated the expression of the receptors MT1 and MT2 and p53 in uterine tissue. All of these factors may contribute to the beneficial effects of melatonin on embryo implantation in mice.

CONCLUSION

Melatonin treatment was associated with beneficial effects in pregnant mice, especially those subjected to long photoperiodic exposure. This was achieved by enhanced embryo implantation. At the molecular level, melatonin administration probably increases the E₂ level during pregnancy and upregulates p53 expression by activating MT1/2 in the uterus. All of the changes may improve the microenvironment of the uterus and, thus, the outcomes of pregnancy.

Melatonin Treatment May Be Able to Restore Menstrual Cyclicity in Women With PCOS: A Pilot Study

The objective of the study was to investigate the effects of 6 months of melatonin administration on clinical, endocrine, and metabolic features of women affected by polycystic ovary syndrome (PCOS). This is a prospective cohort study including 40 normal-weight women with PCOS between January and September 2016, enrolled in an academic research environment. Ultrasonographic pelvic examinations, hirsutism score evaluation, hormonal profile assays, oral glucose tolerance test, and lipid profile at baseline and after 6 months of melatonin administration were performed. Melatonin treatment significantly decreased androgens levels (free androgen index: P < .05; testosterone: P < .01; 17 hydroxyprogesterone: P < .01). Follicle-stimulating hormone levels significantly raised ( P < .01), and anti-Mullerian hormone serum levels significantly dropped after 6 months of melatonin treatment ( P < .01). No significant changes occurred in glucoinsulinemic and lipid parameters after treatment except a significant decrease of low-density lipoprotein cholesterol. Almost 95% of participants experienced an amelioration of menstrual cycles. Until now, only few data have been published about the role of melatonin in women with PCOS. This is the first study focused on the effects of exogenous oral melatonin administration on the clinical, endocrine, and metabolic characteristics of patients with PCOS. After 6 months of treatment, melatonin seems to improve menstrual irregularities and biochemical hyperandrogenism in women with PCOS through a direct, insulin-independent effect on the ovary. Based on our results, melatonin could be considered a potential future therapeutic agent for women affected by PCOS.

Melatonin Reduces Angiogenesis in Serous Papillary Ovarian Carcinoma of Ethanol-Preferring Rats

Angiogenesis is a hallmark of ovarian cancer (OC); the ingrowth of blood vessels promotes rapid cell growth and the associated metastasis. Melatonin is a well-characterized indoleamine that possesses important anti-angiogenic properties in a set of aggressive solid tumors. Herein, we evaluated the role of melatonin therapy on the angiogenic signaling pathway in OC of an ethanol-preferring rat model that mimics the same pathophysiological conditions occurring in women. OC was chemically induced with a single injection of 7,12-dimethylbenz(a)anthracene (DMBA) under the ovarian bursa. After the rats developed serous papillary OC, half of the animals received intraperitoneal injections of melatonin (200 µg/100 g body weight/day) for 60 days. Melatonin-treated animals showed a significant reduction in OC size and microvessel density. Serum levels of melatonin were higher following therapy, and the expression of its receptor MT1 was significantly increased in OC-bearing rats, regardless of ethanol intake. TGFβ1, a transforming growth factor-beta1, was reduced only after melatonin treatment. Importantly, vascular endothelial growth factor (VEGF) was severely reduced after melatonin therapy in animals given or not given ethanol. Conversely, the levels of VEGF receptor 1 (VEGFR1) was diminished after ethanol consumption, regardless of melatonin therapy, and VEGFR2 was only reduced following melatonin. Hypoxia-inducible factor (HIF)-1α was augmented with ethanol consumption, and, notably, melatonin significantly reduced their levels. Collectively, our results suggest that melatonin attenuates angiogenesis in OC in an animal model of ethanol consumption; this provides a possible complementary therapeutic opportunity for concurrent OC chemotherapy.

The role of sex hormones and steroid receptors on female reproductive cancers

Sex steroids have been widely described to be associated with a number of human diseases, including hormone-dependent tumors. Several studies have been concerned about the factors regulating the availability of sex steroids and its importance in the pathophysiological aspects of the reproductive cancers in women. In premenopausal women, large fluctuations in the concentration of circulating estradiol (E2) and progesterone (P4) orchestrate many events across the menstrual cycle. After menopause, the levels of circulating E2 and P4 decline but remain at high concentration in the peripheral tissues. Notably, there is a strong relationship between circulating sex hormones and female reproductive cancers (e.g. ovarian, breast, and endometrial cancers). These hormones activate a number of specific signaling pathways after binding either to estrogen receptors (ERs), especially ERα, ERα36, and ERβ or progesterone receptors (PRs). Importantly, the course of the disease will depend on particular transactivation pathway. Identifying ER- or PR-positive tumors will benefit patients in terms of proper endocrine therapy. Based on hormonal responsiveness, effective prevention methods for ovarian, breast, and endometrial cancers represent a special opportunity for women at risk of malignancies. Hormone replacement therapy (HRT) might significantly increase the risk of these cancer types, and endocrine treatments targeting ER signaling may be helpful against E2-dependent tumors. This review will present the role of sex steroids and their receptors associated with the risk of developing female reproductive cancers, with emphasis on E2 levels in pre and postmenopausal women. In addition, new therapeutic strategies for improving the survival rate outcomes in women will be addressed.

Ovarian sex steroid receptors and sex hormones in androgenized rats

This study evaluated for the first time the effects of different doses of the anabolic steroid nandrolone decanoate (ND) on the expression of ovarian steroid receptors (AR, ER-α (ESR1) and ER-β (ESR2)) and related sex hormones after treatment and recovery periods in adult rats. The animals were injected subcutaneously with doses of ND (1.87, 3.75, 7.5 or 15 mg/kg b.w.) or mineral oil (control group) for 15 days, and the experimental groups were divided into three periods of evaluation: (a) ND treatment for 15 days, (b) ND treatment and recovery for a period of 30 days and (c) ND treatment and recovery for a period of 60 days. Estrous cycle was monitored daily. At the end of each period, rats were killed for collection of blood and ovaries. Persistent diestrus occurred in all rats during ND treatment and after 30-day recovery. The highest dose of ND was able to maintain all rats arrested at diestrus until 60-day recovery. The expression of steroid receptors varied in a dose- and period-dependent manner, having a more pronounced response with the dose of 15 mg ND/kg. ND treatment increased serum levels of testosterone, 17β-estradiol and dihydrotestosterone, especially at the highest doses of 7.5 and 15 mg ND/kg. No change was observed in the levels of follicle-stimulating hormone (FSH), whereas levels of the luteinizing hormone (LH) varied according to the dose and period. In conclusion, the ovarian sex steroid receptors and sex hormones were restored only at lower doses of ND and after a longer period of recovery.

Does melatonin influence the apoptosis in rat uterus of animals exposed to continuous light?

Melatonin has been described as a protective agent against cell death and oxidative stress in different tissues, including in the reproductive system. However, the information on the action of this hormone in rat uterine apoptosis is low. Our objective was to evaluate the effects of melatonin on mechanisms of cell death in uterus of rats exposed to continuous light stress. Twenty adult Wistar rats were divided into two groups: GContr (vehicle control) and GExp which were treated with melatonin (0.4 mg/mL), both were exposed to continuous light for 90 days. The uterus was removed and processed for quantitative real time PCR (qRT-PCR), using PCR-array plates of the apoptosis pathway; for immunohistochemistry and TUNEL. The results of qRT-PCR of GEXP group showed up-regulation of 13 and 7, pro-apoptotic and anti-apoptotic genes, respectively, compared to GContr group. No difference in pro-apoptotic proteins (Bax, Fas and Faslg) expression was observed by immunohistochemistry, although the number of TUNEL-positive cells was lower in the group treated with melatonin compared to the group not treated with this hormone. Our data suggest that melatonin influences the mechanism and decreases the apoptosis in uterus of rats exposed to continuous light.

Apoptosis is triggered by melatonin in an in vivo model of ovarian carcinoma

Apoptosis plays an important role in the treatment of cancer, and targeting apoptosis-related molecules in ovarian cancer (OC) is of great therapeutic value. Melatonin (Mel) is an indoleamine displaying several anti-cancer properties and has been reported to modulate apoptosis signaling in multiple tumor subtypes. We investigated OC and the role of Mel therapy on the pro-apoptotic (p53, BAX, caspase-3, and cleaved caspase-3) and anti-apoptotic (Bcl-2 and survivin) proteins in an ethanol (EtOH)-preferring rat model. To induce OC, the left ovary was injected directly with a single dose of 100 μg 7,12-dimethylbenz(a)anthracene dissolved in 10 μl of sesame oil under the bursa. Right ovaries were used as sham-surgery controls. After developing OC, half of the animals received i.p. injections of Mel (200 μg/100 g BW per day) for 60 days. Body weight gain, EtOH consumption, and energy intake were unaffected by the treatments. Interestingly, absolute and relative OC masses showed a significant reduction after Mel therapy, regardless of EtOH consumption. To accomplish OC-related apoptosis, we first observed that p53, BAX, caspase-3, and cleaved caspase-3 were downregulated in OC tissue while Bcl-2 and survivin were overexpressed. Notably, Mel therapy and EtOH intake promoted apoptosis along with the upregulation of p53, BAX, and cleaved caspase-3. Fragmentation of DNA observed by TUNEL-positive nuclei was also enhanced following Mel treatment. In addition, Bcl-2 was downregulated by the EtOH intake and lower survivin levels were observed after Mel therapy. Taken together, these results suggest that Mel induce apoptosis in OC cells of EtOH-preferring animals.

Melatonin-related genes expressed in the mouse uterus during early gestation promote embryo implantation

Melatonin, a superior antioxidant, is an important molecule which regulates female reproduction due to its receptor-mediated and receptor-independent antioxidant actions. In this study, we investigated the effect of melatonin on early gestation in a mouse model. During early gestation, the expression of the melatonin's rate-limiting enzyme, AANAT, gradually increased - in the uterus while the MT2 melatonin receptor was only expressed at day 2 of gestation and no MT1 was detected. Based on these findings, we conducted a melatonin injection experiment which demonstrated that 15 mg/kg melatonin significantly improved the number of implantation sites and the litter size. Also, the blastocyst and uterus were collected to identify the local action of melatonin. In the melatonin-treated mice, the endometrium was thicker than in the control mice; melatonin also caused an increase in density of uterine glands, and the uterine gland index (UGI) was significantly elevated over that of the control. Serum steroid hormone measurements revealed that at day 6 of gestation (postimplantation), melatonin significantly downregulated the E2 level, with no obvious effects on progesterone. Gene expression assay revealed that melatonin significantly upregulated expression of HB-EGF, a crucial gene involved in implantation as well as its receptor ErbB1 in the blastocyst. In addition, PRA, an important gene which influences the decidual response and luminal cell differentiation, p53, which regulates uterine through leukaemia inhibitory factor (LIF), were both increased after melatonin treatment. These data suggest that melatonin and its MT2 receptor influence early gestation. Exogenous melatonin treatment can improve mouse embryo implantation and litter size, which may have important applications in human reproductive health and animal husbandry.

Melatonin attenuates the TLR4-mediated inflammatory response through MyD88- and TRIF-dependent signaling pathways in an in vivo model of ovarian cancer

Background

Toll-like receptors (TLRs) are effector molecules expressed on the surface of ovarian cancer (OC) cells, but the functions of the TLR2/TLR4 signaling pathways in these cells remain unclear. Melatonin (mel) acts as an anti-inflammatory factor and has been reported to modulate TLRs in some aggressive tumor cell types. Therefore, we investigated OC and the effect of long-term mel therapy on the signaling pathways mediated by TLR2 and TLR4 via myeloid differentiation factor 88 (MyD88) and toll-like receptor-associated activator of interferon (TRIF) in an ethanol-preferring rat model.

Methods

To induce OC, the left ovary of animals either consuming 10% (v/v) ethanol or not was injected directly under the bursa with a single dose of 100 μg of 7,12-dimethylbenz(a)anthracene (DMBA) dissolved in 10 μL of sesame oil. The right ovaries were used as sham-surgery controls. After developing OC, half of the animals received i.p. injections of mel (200 μg/100 g b.w./day) for 60 days.

Results

Although mel therapy was unable to reduce TLR2 levels, it was able to suppress the OC-associated increase in the levels of the following proteins: TLR4, MyD88, nuclear factor kappa B (NFkB p65), inhibitor of NFkB alpha (IkBα), IkB kinase alpha (IKK-α), TNF receptor-associated factor 6 (TRAF6), TRIF, interferon regulatory factor 3 (IRF3), interferon β (IFN-β), tumor necrosis factor alpha (TNF-α), and interleukin (IL)-6. In addition, mel significantly attenuated the expression of IkBα, NFkB p65, TRIF and IRF-3, which are involved in TLR4-mediated signaling in OC during ethanol intake.

Conclusion

Collectively, our results suggest that mel attenuates the TLR4-induced MyD88- and TRIF-dependent signaling pathways in ethanol-preferring rats with OC.

Melatonin Attenuates Her-2, p38 MAPK, p-AKT, and mTOR Levels in Ovarian Carcinoma of Ethanol-Preferring Rats

Epidermal growth factor receptors 2 (Her-2) and 4 (Her-4) are closely associated with ovarian cancer (OC) progression and metastasis, and a more complete understanding of these signaling pathways allow the development of new therapeutic strategies. Melatonin (Mel) is recognized as having several anticancer properties and has been reported to modulate Her-2 system in aggressive tumors. Here, we investigated OC and the role of Mel therapy on the Her-2- and Her-4-signaling pathway related to downstream molecules in an ethanol-preferring rat model. To induce OC, the left ovary was injected directly with a single dose of 100 µg 7,12-dimethylbenz(a)anthracene (DMBA) dissolved in 10 µL of sesame oil under the bursa. Right ovaries were used as sham-surgery controls. After developing OC, half of the animals received i.p. injections of Mel (200 µg/100 g b.w./day) for 60 days. While Mel therapy was unable to reduce Her-4 and phosphoinositide 3-kinase (PI3K) levels, it was able to suppress the OC-related increase in the levels of the Her-2, p38 mitogen-activated protein kinases (p38 MAPK), protein kinase B (phospho-AKT), and mammalian target of rapamycin (mTOR). In addition, Mel significantly attenuated the expression of Her-2, p38 MAPK, and p-AKT, which are involved in OC signaling during ethanol intake. Collectively, our results suggest that Mel attenuates the Her-2-signaling pathway in OC of ethanol-preferring rats, providing an effective contribution for further development of adjuvant therapies.