Melatonin and reproduction revisited

Leptin mediates the effects of melatonin on female reproduction in mammals

Melatonin is a natural molecule produced in the pineal gland and other tissues. It participates in numerous biological activities including the regulation of reproduction. However, the mechanism by which melatonin affects mammalian female reproductive performance is not fully investigated. In the present study, it was observed that melatonin positively regulated the level of leptin in female mouse and pig. To understand the potential association between melatonin and leptin on the female reproductive activities, the melatonin receptor 1 MT1 knockout (MT1^-/- ) mouse and Leptin knockout (Leptin^-/- ) pig were created. It was found that the deficiency of M T1 caused low leptin secretion and litter size in mouse. Meanwhile, the deletion of leptin in pig did not affect melatonin production, but significantly reduced follicle-stimulating hormone, estradiol-17β (E2), and Luteinizing hormone and increased progesterone (P) at estrum stage, which also led to smaller litter size than that in control. Melatonin treatment increased the production of leptin in pigs, while the supplementary of leptin was also able to improve the ovulation number, polar body rates, and expression of StAR in MT1^-/- females. Therefore, it is first time, we described that leptin is the downstream target of melatonin in regulating female reproduction. These findings provide the novel information on the physiology of melatonin in animal reproduction.

Melatonin prevents early pituitary dysfunction induced by sucrose-rich diets

While physiological levels of glucocorticoids are required to ensure proper functions of the body, consistently high levels may engender several deleterious consequences. We have previously shown an increase in the activity of the hypothalamic-pituitary-adrenal (HPA) axis in rats fed sucrose-rich diets (SRD). The main goal of this study was to analyze the processes involved in the modulation of the pituitary production of ACTH by SRD, and to test melatonin as a possible therapeutic agent for the prevention of the HPA axis dysfunction. Male Wistar rats were fed standard chow and either SRD (30% sucrose in the drinking water) or plain water for three weeks. Melatonin was administered as subcutaneous pellets. Results showed that SRD treatment induced an increase in systemic ACTH and corticosterone levels and a decrease in melatonin levels. In the pituitary gland, we also detected an increase in the expression levels of proopiomelanocortin (POMC) that was accompanied by increased levels of: lipoperoxides, nitro-tyrosine modified proteins, catalase, heme oxygenase-1, interleukin-1β mRNA, and by an increase in the tissue number of inflammatory cells (F4/80 and Iba-1 positive cells). Melatonin treatment prevented all these systemic and pituitary changes as well as the increase in POMC expression induced by incubation of AtT-20 corticotrophs with conditioned media obtained from stimulated macrophages. In conclusion, stimulation of POMC/ACTH production in rats fed a SRD could involve the generation of oxidative stress and inflammation in the pituitary gland. Melatonin treatment prevented these effects and normalized the activity of the HPA axis.

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.

The reduction of melatonin levels is associated with the development of preeclampsia: a meta-analysis

OBJECTIVE

The aim of this analysis was to demonstrate the association between melatonin levels and the development of preeclampsia.

METHODS

Standardized mean difference (SMD) with 95% confidence interval (CI) was calculated using a random effects model.

RESULTS

The pooled SMD between case and control was 1.40 (95% CI: 0.26, 2.55; P = 0.02). And the pooled SMD between mild PE and severe PE was 5.25 (95% CI: 1.5, 9.01; P = 0.006).

CONCLUSION

The meta-analysis illustrated that melatonin concentration was significantly lower in women with preeclampsia, and correlated with the severity of the disease.

Intrafollicular melatonin concentration is elevated in patients with ovarian hyperstimulation syndrome (OHSS) and can serve as an important predictor of OHSS

PURPOSE

Melatonin is an important factor in regulating numerous processes in human female reproduction. The aim of the present study was to compare melatonin levels in the follicular fluid (FF) of ovarian hyperstimulation syndrome (OHSS) women with those of non-OHSS women undergoing in vitro fertilization (IVF)-embryo transfer and to evaluate the relationship between FF melatonin levels and IVF outcomes in these women.

METHODS

We determined FF melatonin levels in 20 OHSS women and 23 non-OHSS women on oocyte retrieval day.

RESULTS

OHSS patients had significantly higher melatonin levels as compared to the non-OHSS women (P < 0.001). In addition, melatonin levels of the patients were significantly positively correlated with antral follicle count (AFC), serum anti-Müllerian hormone (AMH) levels, serum estradiol (E₂) levels on human chorionic gonadotropin (HCG) administration day, number of retrieved oocytes, total fertilized oocytes, normally fertilized oocytes, cleaved zygotes, top quality embryos on day 3, blastocysts obtained and embryos suitable for transplantation (day 3 embryos + day 5/6 blastocysts) (P < 0.05). While, the intrafollicular melatonin levels were significantly negatively correlated with age, basal serum follicle-stimulating hormone (FSH) levels, serum FSH levels on HCG administration day (P < 0.01). Since younger women with more AFC, higher AMH levels, higher serum E₂ levels and larger number of retrieved oocytes are much easier to encounter OHSS, while FF melatonin levels are significantly correlated with these five indices in our study, we propose that intrafollicular melatonin concentration can also be an important predictor of OHSS.

CONCLUSIONS

This is the first demonstration that FF melatonin levels were significantly higher in OHSS patients than in non-OHSS group and FF melatonin levels may serve as an important predictor of OHSS.

Melatonin-induced demethylation of antioxidant genes increases antioxidant capacity through RORα in cumulus cells of prepubertal lambs

Physical damage and oxidative stress may occur in prepubertal cumulus cells, due to insufficient glutathione synthesis. To determine potential epigenetic mechanisms related to antioxidant effects of melatonin on ovine prepubertal cumulus cells, 30 lambs, 4-wk-old were randomly allocated into two groups: a control (C, n = 20) group and a melatonin (M, n = 10) group given a subcutaneous implant containing 18 mg melatonin. All lambs were superovulated (250 IU FSH and 250 IU eCG). Cumulus cells from germinal vesicle stage cumulus oocyte complexes (COCs) were collected by ovarian follicular aspiration and dissociated with hyaluronidase. Compared to the C group, the M group had greater superovulation, better antioxidant capacity, a higher proportion of fully expanded COCs and a lower proportion of apoptotic cumulus cells (P < 0.05). Melatonin up-regulated mRNA expression of genes for melatonin receptors MT1 and nuclear binding site RORα, antioxidants (SOD1, GPx4 and CAT) and cumulus cell expansion (PTX3, HAS2 and PTGS2), as well as Bcl2, but down-regulated expression of Bax (P < 0.05). Regarding epigenetics, there were less methylation at five CpG sites of SOD1, three CpG sites of GPx4 and two CpG sites of CAT in M versus C groups (P <  0.05), leading to lower total methylation of SOD1, GPx4 and CAT promoters region on M group (P < 0.05). In a mechanistic study, addition of MT1 or RORα antagonist increased ROS and MDA concentrations, but decreased T-AOC, GPx, CAT and T-SOD concentrations (P < 0.05), whereas there were no significant difference between the melatonin and MT2 antagonist treatment groups for T-AOC, GPx, CAT and T-SOD concentrations. Furthermore, addition of RORα agonist decreased total DNA methylation of SOD1, GPx4 and CAT, with no significant difference after MT1 agonist treatment. These studies provided new information regarding epigenetic mechanisms by which melatonin promoted ovine prepubertal cumulus cells antioxidant through RORα, both in vitro and in vivo.

Melatonin protects against paraquat-induced damage during in vitro maturation of bovine oocytes

Paraquat (PQ), a broad-spectrum agricultural pesticide, causes cellular toxicity by increasing oxidative stress levels in various biological systems, including the reproductive system. PQ exposure causes embryotoxicity and reduces the developmental abilities of embryos. However, there is little information regarding the toxic effects of PQ on oocyte maturation. In this study, we studied the toxic effects of PQ exposure and the effects of melatonin on PQ-induced damage in bovine oocytes. PQ exposure disrupted nuclear and cytoplasmic maturation, which was manifested as decreased cumulus cell expansion, reduced first polar body extrusion, and abnormal distribution patterns of cortical granules and mitochondria. In addition, PQ treatment severely disrupted the ability of the resulted in vitro-produced embryos to develop to the blastocyst stage. Moreover, PQ exposure significantly increased the intracellular reactive oxygen species (ROS) level and early apoptotic rate, and decreased the glutathione (GSH) level, antioxidative CAT and GPx4 mRNA, and apoptotic-related Bcl-2/Bax mRNA ratio. These results indicated that PQ causes reproductive toxicity in bovine oocytes. Melatonin application resulted in significant protection against the toxic effects of PQ in PQ-exposed oocytes. The mechanisms underlying the role of melatonin included the inhibition of PQ-induced p38 mitogen-activated protein kinase (MAPK) activation, and restoration of abnormal trimethyl-histone H3 lysine 4 (H3K4me3) and trimethyl-histone H3 lysine 9 (H3K9me3) levels. These results reveal that melatonin serves as a powerful agent against experimental PQ-induced toxicity during bovine oocyte maturation and could form a basis for further studies to develop therapeutic strategies against PQ poisoning.

The effects of melatonin administration in different times of day on the brown adipose tissue in rats with high-calorie diet-induced obesity

The aim of our study was to determine morpho-functional state (area of nucleus, brown adipocytes and also area and number of lipid droplets in each cells, general optical density of tissue) of brown adipose tissue in rats with high-calorie (high fat) dietinduced obesity after melatonin administration in different time of the day (morning and evening). Melatonin was administered daily by gavage for 7 weeks in dose 30 mg/kg either 1 h after lights-on (ZT01) or 1 h before lights-off (ZT11) rats with high-calorie diet (HCD). Besides morphometric parameters as well were measured related visceral fat weight and related brown adipose tissue mass. Rats with HCD had huge changes in brown adipocytes morphology, which summarized in become resembles of classical white adipocytes: grown lipid droplets and cells area, but goes down lipid droplets number and optical density of brown adipose tissue. In general brown adipose tissue with above mentioned characteristic from HCD rats lose their ability to conduct strongly thermoproduction function. After melatonin used in rats with HCD arise leveling of pathological changes, which associated with consumption of HCD. Namely, in groups HCD ZT01 and HCD ZT11 we obtain decreased cells and lipid droplets area, increased lipid droplets number and optical density of brown adipose tissue, in relation to group HCD. Therese received changes has evidence about functionally active brown adipose tissue state, which can also dissipate of exceed energy (lipids – triacylglycerols) amount into whole organism during heat production for avoid to its storage in white adipose tissue and in outside adipose tissue. In addition, evening administration of melatonin (group HCD ZT11) demonstrate more activated state of brown adipose tissueand also related visceral weight gain less, than morning(group HCD ZT01). In conclusions, melatonin influence on morpho-functional state brown adipose tissue in rats with HCD, moreover evening administration can use for obesity therapy via its strong action on activate brown adipocytes.

Pineal gland calcification under hypoxic conditions

The pineal gland (glandula pinealis) is neuroendocrine gland located at the epithalamus of the brain secreting melatonin. The aim of this study was to explore effects of prenatal hypoxia in rats at the age of 33 weeks on the occurrence of pineal gland calcification. Distribution and chemical composition of calcerous material by light, scanning and transmission electron microscopy was investigated. Melatonin concentrations in blood plasma by direct radioimmunoassay were measured. Rats were exposed to prenatal hypoxia for 12 h at day 20 of development and second group to prenatal hypoxia for 2x8 h at days 19 and 20 of development. Vacuoles of intracellular edema in the pineal samples after 12 h hypoxia were found. Their size ranges up to 30 µm. Some of them were filled with the flocculent and fibrous material. Samples of pineal glands after 2 x 8 h hypoxia revealed the pericellular edema of pinealocytes. The amount of calcium rich particles in 2 x 8 h hypoxia group was lower than in 12 h hypoxia group. Plasma melatonin levels did not differ between control and both hypoxia groups. We concluded that calcification is a process induced by osteoblasts and osteocytes with melatonin as a promotor and it is favored under hypoxic conditions.

Melatonin Inhibits Formation of Mitochondrial Permeability Transition Pores and Improves Oxidative Phosphorylation of Frozen-Thawed Ram Sperm

Structural and functional damages to mitochondria of frozen-thawed sperm are a typical cryoinjury, with mitochondrial permeability transition pore (MPTP) formation being the hallmark change. Mitochondria are both a primary synthesis site and principle target for melatonin; this compound can directly inhibit MPTP formation and therefore confer protection at a mitochondrial level. The objective was to determine effects of melatonin on MPTP opening, viability, motility, and oxidative phosphorylation (OXPHOS) of frozen-thawed ram sperm. Ram semen was diluted in glucose-egg yolk buffer with 0 or 10^-7 M melatonin (frozen and frozen + melatonin groups, respectively) and slow frozen, with fresh semen as Control. In frozen-thawed sperm, melatonin inhibited MPTP opening and lactate concentrations and improved sperm viability, motility, acetyl-CoA concentration and adenosine triphosphate (ATP) production. With regard to the underlying physiological mechanism, melatonin suppressed movement of citrate synthase, isocitrate dehydrogenase, oxoglutarate dehydrogenase complex, and F0F1-ATP synthase permeability from mitochondrial to cytosolic fractions induced by MPTP opening; furthermore, it increased mRNA expressions of respiratory chain complex components and activities of complexes I, II, III, and IV and thereby improved oxygen consumption capacity in frozen-thawed sperm. In conclusion, melatonin improved OXPHOS of frozen-thawed ram sperm, attributed to inhibition of cryopreservation-induced MPTP opening.

Targeting the vascular dysfunction: Potential treatments for preeclampsia

Preeclampsia is a pregnancy-specific disorder, primarily characterized by new-onset hypertension in combination with a variety of other maternal or fetal signs. The pathophysiological mechanisms underlying the disease are still not entirely clear. Systemic maternal vascular dysfunction underlies the clinical features of preeclampsia. It is a result of oxidative stress and the actions of excessive anti-angiogenic factors, such as soluble fms-like tyrosine kinase, soluble endoglin, and activin A, released by a dysfunctional placenta. The vascular dysfunction then leads to impaired regulation and secretion of relaxation factors and an increase in sensitivity/production of constrictors. This results in a more constricted vasculature rather than the relaxed vasodilated state associated with normal pregnancy. Currently, the only effective "treatment" for preeclampsia is delivery of the placenta and therefore the baby. Often, this means a preterm delivery to save the life of the mother, with all the attendant risks and burdens associated with fetal prematurity. To lessen this burden, there is a pressing need for more effective treatments that target the maternal vascular dysfunction that underlies the hypertension. This review details the vascular effects of key drugs undergoing clinical assessment as potential treatments for women with preeclampsia.

The effect of inflammation on the synthesis of luteinizing hormone and gonadotropin-releasing hormone receptor expression in the pars tuberalis of ewe during different photoperiodic conditions

The study was designed to determine the effect of endotoxin-induced inflammation on luteinizing hormone (LH) synthesis and gonadotropin-releasing hormone (GnRH) receptor expression in the pars tuberalis (PT) of ewes during anestrous season and follicular phase taking into account the time of the day. Moreover, the effect of inflammation on the release of melatonin and its type I receptor gene expression in the PT was also determined. Lipopolysaccharide administration reduced nocturnal release of melatonin only during anestrous season, but it did not influence the gene expression of melatonin type I receptor in the PT. Inflammation inhibited nocturnal increase in the gene and protein expression of LH in the PT during the follicular phase. Since in day-active species nocturnal accumulation of LH protein in the pituitary precedes the LH surge, this lowering of LH content may delay or disturb the surge occurrence. Suppression of LH secretion could have resulted from the decreased sensitivity of the PT on the action of GnRH because inflammation reduced GnRH receptor expression. The study suggests that the ability of endotoxin to suppress LH synthesis in the PT may be another mechanism by which inflammation disturbs reproductive neuroendocrine axis in seasonal breeders.

Beneficial effects of melatonin on in vitro embryo production from juvenile goat oocytes

Melatonin is a universal antioxidant that improves in vitro embryo production in several species. The aims of this study were to determine the melatonin concentration in the ovarian follicular fluid (FF) of juvenile goats and the effect of melatonin during in vitro maturation (IVM) on embryo development. The FF melatonin concentration was 0.57--1.07×10-9 M, increasing with follicular diameter. Oocytes were matured, fertilised and cultured under conventional conditions. Blastocyst development, embryo quality and levels of reactive oxygen species (ROS) and reduced glutathione were assessed. In Experiment 1 different melatonin concentrations (10-3, 10-7, 10-9, 10-11 M) were added to the IVM medium, which contained cysteamine as antioxidant, and no differences were observed. In Experiment 2, melatonin (10-7 M) was tested in the presence or absence of cysteamine (experimental groups: melatonin, cysteamine, melatonin+cysteamine, non-antioxidant). The melatonin group presented a higher blastocyst rate than the non-antioxidant group (28.9 vs 11.7%; P<0.01) and a higher total cell number than the cysteamine group (225.1 vs 129.0; P<0.05). Oocytes from the melatonin and cysteamine groups had lower ROS levels than those from the non-antioxidant group. This study shows that melatonin is an interesting tool for improving oocyte competence in juvenile goats as it increases embryo production and quality.

Melatonin protects prepuberal testis from deleterious effects of bisphenol A or diethylhexyl phthalate by preserving H3K9 methylation

A growing number of couples experience fertility issues with almost half being due to malefactors. The exposure to toxic environmental contaminants, such as endocrine disruptors (EDs), has been shown to negatively affect male fertility. EDs are present in the environment, and exposure to these toxins results in the failure of spermatogenesis. The deleterious effects of EDs on spermatogenesis have been well documented, whereas improvement of infertility associated with spermatogenesis defects remains a great challenge. Herein, we report that in vitro exposure of prepuberal mouse testes to two well-known endocrine disruptors (EDs), bisphenol A (BPA) or diethylhexyl phthalate (DEHP), impairs spermatogenesis with perturbing self-renewal, spermatogonia activity, and meiosis. Evidence indicates that such effects are likely due, at least in part, to decreased G9a-dependent H3K9 di-methylation. Of note, we found that melatonin (MLT) protected the testis from the negative ED impacts with preserving spermatogonia stem and meiotic cells, along with maintaining normal H3K9 di-methylation in these cells. Taken together, this work documents that BPA and EDHP adversely affect prepuberal spermatogenesis and perturb crucial epigenetic activities in male germ cells and highlight the protective ability of MLT.

Effects of light at night on laboratory animals and research outcomes

Light has substantial influences on the physiology and behavior of most laboratory animals. As such, lighting conditions within animal rooms are potentially significant and often underappreciated variables within experiments. Disruption of the light/dark cycle, primarily by exposing animals to light at night (LAN), disturbs biological rhythms and has widespread physiological consequences because of mechanisms such as melatonin suppression, sympathetic stimulation, and altered circadian clock gene expression. Thus, attention to the lighting environment of laboratory animals and maintaining consistency of a light/dark cycle is imperative for study reproducibility. Light intensity, as well as wavelength, photoperiod, and timing, are all important variables. Although modern rodent facilities are designed to facilitate appropriate light cycling, there are simple ways to modify rooms to prevent extraneous light exposure during the dark period. Attention to lighting conditions of laboratory animals by both researchers and research care staff ensures best practices for maintaining animal welfare, as well as reproducibility of research results. (PsycINFO Database Record

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.

Melatonin affects the motility and adhesiveness of in vitro capacitated boar spermatozoa via a mechanism that does not depend on intracellular ROS levels

This work sought to address the effects of melatonin during in vitro capacitation (IVC) and progesterone-induced acrosome exocytosis (IVAE) in boar spermatozoa. With this purpose, two different experiments were set. In the first one, IVC and IVAE were induced in the absence or presence of melatonin, which was added either at the start of IVC or upon triggering the IVAE with progesterone. Different parameters were evaluated, including intracellular levels of peroxides and superoxides, free cysteine radicals and distribution of specific lectins. While melatonin neither affected most capacitation-associated parameters nor IVAE, it dramatically decreased sperm motility, with a maximal effect at 5 μm. This effect was accompanied by a significant increase in the percentage of agglutinated spermatozoa, which was independent from noticeable changes in the distribution of lectins. Levels of free cysteine radicals were significantly lower in melatonin treatments than in the control after 4 h of incubation in capacitating medium. The second experiment evaluated the effects of melatonin on in vitro fertilising ability of boar spermatozoa. Spermatozoa previously subjected to IVC in the presence of 1 μm melatonin and used for in vitro fertilisation exhibited less ability to bind the zona pellucida (ZP) and higher percentages of monospermy. In conclusion, melatonin affects sperm motility and the stability of nucleoprotein structure and also modulates the ability of in vitro capacitated boar spermatozoa to bind the oocyte ZP. However, such effects do not seem to be related to either its antioxidant properties or changes in the sperm glycocalix.

Morphology and quantification of sheep pineal glands at pre-pubertal, pubertal and post-pubertal periods

The pineal gland is a neuroendocrine organ associated with photoperiodic regulation in mammals. The aim of this study was to evaluate the pineal gland at the pre-pubertal, pubertal and post-pubertal periods by means of morphology and stereology. The study examined at total of 24 ovine pineal glands collected from healthy female Akkaraman breed. Thick sections (40 μm) were cut and treated with synaptophysin. Following each thick section, six consecutive sections at a thickness of 5 μm were cut. Each thin section was stained with one of the following dyes: Crossman's modified triple dye, glial fibrillary acidic protein (GFAP), melatonin marker, periodic acid-Schiff, Von Kossa and AgNOR. The pineal gland volume was measured using Cavalieri's method. The optical fractionator was used to estimate the total number of pinealocytes. The percentage of parenchyma and connective tissue and degree of vascularization were estimated by the area fraction fractionator method. The pineal gland volumes in the pre-pubertal, pubertal and post-pubertal groups were 7.53 ± 1.715 mm³ , 11.20 ± 1.336 mm³ and 17.75 ± 1.188 mm³ , respectively (p < .5). The number of pinealocytes in the pre-pubertal, pubertal and post-pubertal groups was 3,244,000 ± 228,076, 4,438,000 ± 243,610, 7,381,766 ± 406,223, respectively (p < .05). The glands of the post-pubertal group contained the highest amount of connective tissue (11.49 ± 2.103%; p < .5) and the largest GFAP staining area (p < .05). The melatonin staining density was the highest in the pubertal group. The density of lipofuscin staining was higher in the pubertal and post-pubertal groups.

Cardiovascular Benefits of Dietary Melatonin: A Myth or a Reality?

The role of the diet as well as the impact of the dietary habits on human health and disease is well established. Apart from its sleep regulatory effect, the indoleamine melatonin is a well-established antioxidant molecule with multiple health benefits. Convincing evidence supports the presence of melatonin in plants and foods with the intake of such foods affecting circulating melatonin levels in humans. While numerous actions of both endogenous melatonin and melatonin supplementation are well described, little is known about the influence of the dietary melatonin intake on human health. In the present review, evidence for the cardiovascular health benefits of melatonin supplementation and dietary melatonin is discussed. Current knowledge on the biological significance as well as the underlying physiological mechanism of action of the dietary melatonin is also summarized. Whether dietary melatonin constitutes an alternative preventive treatment for cardiovascular disease is addressed.

Melatonin-Mediated Development of Ovine Cumulus Cells, Perhaps by Regulation of DNA Methylation

Cumulus cells of pre-pubertal domestic animals are dysfunctional, perhaps due to age-specific epigenetic events. This study was designed to determine effects of melatonin treatment of donors on methylation modification of pre-pubertal cumulus cells. Cumulus cells from germinal vesicle stage cumulus oocyte complexes (COCs) were collected from eighteen lambs which were randomly divided into control group (C) and melatonin group given an 18 mg melatonin implant subcutaneous (M). Compared to the C group, the M group had higher concentrations of melatonin in plasma and follicular fluid (p < 0.05), greater superovulation, a higher proportion of fully expanded COCs, and a lower proportion of apoptotic cumulus cells (p < 0.05). Real-time PCR results showed that melatonin up-regulated expression of genes MT1, Bcl2, DNMT1, DNMT3a and DNMT3b, but down-regulated expression of genes p53, Caspase 3 and Bax (p < 0.05). Furthermore, melatonin increased FI of FITC (global methylation level) on cumulus cells (p < 0.05). To understand the regulation mechanism, the DNMTs promoter methylation sequence were analyzed. Compared to the C group, although there was less methylation at two CpG sites of DNMT1 (p < 0.05) and higher methylation at two CpG sites of DNMT3a (p < 0.05), there were no significant differences in methylation of the detected DNMT1 and DNMT3a promoter regions. However, there were lower methylation levels at five CpG sites of DNMT3b, which decreased methylation of detected DNMT3b promoter region on M group (p < 0.05). In conclusion, alterations of methylation regulated by melatonin may mediate development of cumulus cells in lambs.

Prostaglandins in teleost ovulation: A review of the roles with a view to comparison with prostaglandins in mammalian ovulation

Prostaglandins are well known to be central regulators of vertebrate ovulation. Studies addressing the role of prostaglandins in mammalian ovulation have established that they are involved in the processes of oocyte maturation and cumulus oocyte complex expansion. In contrast, despite the first indication of the role of prostaglandins in teleost ovulation appearing 40 years ago, the mechanistic background of their role has long been unknown. However, studies conducted on medaka over the past decade have provided valuable information. Emerging evidence indicates an indispensable role of prostaglandin E₂ and its receptor subtype Ptger4b in the process of follicle rupture. In this review, we summarize studies addressing the role of prostaglandins in teleost ovulation and describe recent advances. To help understand differences from and similarities to ovulation in mammalian species, the findings on the roles of prostaglandins in mammalian ovulation are discussed in parallel.

Melatonin reduces apoptotic cells, SOD2 and HSPB1 and improves the in vitro production and quality of bovine blastocysts

Effects of adding different concentrations of melatonin (10^-7 , 10^-9 and 10^-11  M) to maturation (Experiment 1; Control, IVM + 10^-7 , IVM + 10^-9 , IVM + 10^-11 ) and culture media (Experiment 2; Control, IVC + 10^-7 , IVC + 10^-9 , IVC + 10^-11 ) were evaluated on in vitro bovine embryonic development. The optimal concentration of melatonin (10^-9  M) from Experiments 1-2 was tested in both maturation and/or culture media of Experiment 3 (Control, IVM + 10^-9 , IVC + 10^-9 , IVM/IVC + 10^-9 ). In Experiment 1, maturated oocytes from Control and IVM + 10^-9 treatments showed increased glutathione content, mitochondrial membrane potential and percentage of Grade I blastocysts (40.6% and 43%, respectively). In Experiment 2, an increase in the percentage of Grade I blastocysts was detected in IVC + 10^-7 (43.5%; 56.7%) and IVC + 10^-9 (47.4%; 57.4%). Moreover, a lower number and percentage of apoptotic cells in blastocysts were observed in the IVC + 10^-9 group compared to Control (3.8 ± 0.6; 3.6% versus 6.1 ± 0.6; 5.3%). In Experiment 3, the IVC + 10^-9 treatment increased percentage of Grade I blastocysts with a lower number of apoptotic cells compared to IVM/IVC + 10^-9 group (52.6%; 3.0 ± 0.5 versus 46.0%; 5.4 ± 1.0). The IVC + 10^-9 treatment also had a higher mRNA expression of antioxidant gene (SOD2) compared to the Control, as well as the heat shock protein (HSPB1) compared to the IVM + 10^-9 . Reactive oxygen species production was greater in the IVM/IVC + 10^-9 treatment group. In conclusion, the 10^-9  M concentration of melatonin and the in vitro production phase in which it is used directly affected embryonic development and quality.

Melatonin up-regulates the expression of the GATA-4 transcription factor and increases testosterone secretion from Leydig cells through RORα signaling in an in vitro goat spermatogonial stem cell differentiation culture system

Because androgen function is regulated by its receptors, androgen-androgen receptor signaling is crucial for regulating spermatogenesis. Androgen is mainly testosterone secreted by testis. Based on the results of early studies in goats, the administration of melatonin over an extended period of time increases steroid production, but the underlying mechanism remains unclear. Here, we report the expression of the melatonin membrane receptors MT1 and MT2 and the retinoic acid receptor-related orphan receptor-alpha (RORα) in the goat testis. An in vitro differentiation system using spermatogonial stem cells (SSCs) cultured in the presence of testicular somatic cells was able to support the formation of sperm-like cells with a single flagellum. The addition of 10^-7 M melatonin to the in vitro culture system increased RORα expression and considerably improved the efficiency of haploid cell differentiation, and the addition of the RORα agonist CGP52608 significantly increased the testosterone concentration and expression of GATA binding factor 4 (GATA-4). Furthermore, inhibitors of melatonin membrane receptors and a RORα antagonist (T0901317) also led to a considerable reduction in the efficiency of haploid spermatid formation, which was coupled with the suppression of GATA-4 expression. Based on these results, RORα may play a crucial role in enhancing melatonin-regulated GATA-4 transcription and steroid hormone synthesis in the goat spermatogonial stem cell differentiation culture system.

Maternal administration of melatonin exerts short- and long-term neuroprotective effects on the offspring from lipopolysaccharide-treated mice

Preterm birth is a major contributor to early and delayed physical and cognitive impairment. Epidemiological and experimental data indicate that maternal infections are a significant and preventable cause of preterm birth. Recently, melatonin has been suggested to exert neuroprotective effects in several models of brain injury. Here, we sought to investigate whether the administration of melatonin is able to prevent lipopolysaccharide (LPS)-induced fetal brain damage in a model of LPS-induced preterm labor. For this purpose, 15-day pregnant BALB/c mice received intraperitoneally 2 doses of LPS or vehicle: the first one at 10:00 hours (0.26 mg/kg) and the second at 13:00 hours (0.52 mg/kg). On day 14 of pregnancy, a group of mice was subcutaneously implanted with a pellet of 25 mg melatonin. This experimental protocol resulted in 100% of preterm birth and pup death in the LPS group and a 50% of term birth and pup survival in the melatonin + LPS group. In the absence of melatonin, fetuses from LPS-treated mothers showed histological signs of brain damage, microglial/macrophage activation, and higher levels of IL-1β, inducible nitric oxide synthase (NOS), and neuronal NOS mRNAs as well as increased histone acetyltransferase activity and histone H3 hyperacetylation. In contrast, antenatal administration of melatonin prevented LPS-induced fetal brain damage. Moreover, when behavioral traits were analyzed in the offspring from control, melatonin, and melatonin + LPS, no significant differences were found, suggesting that melatonin prevented LPS-induced long-term neurodevelopmental impairments. Collectively, our results suggest that melatonin could be a new therapeutic tool to prevent fetal brain damage and its long-term consequences induced by maternal inflammation.

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.

Participation of MT3 melatonin receptors in the synergistic effect of melatonin on cytotoxic and apoptotic actions evoked by chemotherapeutics

BACKGROUND

Melatonin has antitumor activity via several mechanisms including its antiproliferative and proapoptotic effects in addition to its potent antioxidant actions. Therefore, melatonin may be useful in the treatment of tumors in association with chemotherapy drugs.

PURPOSE AND METHODS

This study was performed to study the role of melatonin receptors on the cytotoxicity and apoptosis induced by the chemotherapeutic agents cisplatin and 5-fluorouracil in two tumor cell lines, such as human colorectal cancer HT-29 cells and cervical cancer HeLa cells.

RESULTS

We found that both melatonin and the two chemotherapeutic agents tested induced a decrease in HT-29 and HeLa cell viability. Furthermore, melatonin significantly increased the cytotoxic effect of chemotherapeutic agents, particularly, in 5-fluorouracil-challenged cells. Stimulation of cells with either of the two chemotherapeutic agents in the presence of melatonin further increased caspase-3 activation. Concomitant treatments with melatonin and chemotherapeutic agents augmented the population of apoptotic cells compared to the treatments with chemotherapeutics alone. Blockade of MT1 and/or MT2 receptors with luzindole or 4-P-PDOT was unable to reverse the enhancing effects of melatonin on both cytotoxicity, caspase-3 activation and the amount of apoptotic cells evoked by the chemotherapeutic agents, whereas when MT3 receptors were blocked with prazosin, the synergistic effect of melatonin with chemotherapy on cytotoxicity and apoptosis was reversed.

CONCLUSION

Our findings provided evidence that in vitro melatonin strongly enhances chemotherapeutic-induced cytotoxicity and apoptosis in two tumor cell lines, namely HT-29 and HeLa cells and, this potentiating effect of melatonin is mediated by MT3 receptor stimulation.

Profile and reproductive roles of seminal plasma melatonin of boar ejaculates used in artificial insemination programs

Melatonin (MLT) is present in seminal plasma (SP) of mammalian species, including pigs, and it is credited with antioxidant properties. This study aims to identify the sources of variation and the role of boar SP MLT on sperm quality and functionality and in vivo fertilizing ability of liquid-stored semen doses used in AI programs. The SP MLT was measured using an ELISA kit in a total of 219 ejaculates collected from 76 boars, and reproductive records of 5,318 AI sows were recorded. Sperm quality was assessed according to motility (computer-aided sperm analysis) and viability (cytometry evaluation). Sperm functionality was assessed according to the cytometric determination of intracellular HO generation, total and mitochondrial O production, and lipid peroxidation in liquid AI semen samples stored at 17°C over 144 h. The concentration of SP MLT differed among seasons ( < 0.01) and day length periods ( < 0.001) of the year, demonstrating that the ejaculates collected during the increasing day length period (9.80 ± 1.38 pg/mL, range: 2.75-21.94) had lower SP MLT concentrations than those collected during the decreasing day length period (16.32 ± 1.67 pg/mL, range: 5.02-35.61). The SP MLT also differed ( < 0.001) among boars, among ejaculates within boar, and among portions within the ejaculate, demonstrating that SP from the first 10 mL of sperm-rich ejaculate fraction (SRF) exhibited lower MLT concentrations than post-SRF. The SP MLT was negatively related ( < 0.001) to mitochondrial O production in viable sperm. The SP MLT did not differ among AI boars ( = 14) hierarchically grouped according to high and low fertility outcomes. In conclusion, SP MLT concentration in AI boars varies depending on the season of ejaculate collection and differs among boars, ejaculates within boar, and portions within ejaculate. The SP MLT may act at the mitochondrial level of sperm by reducing the generation of O. However, this antioxidant role of SP MLT was not reflected in sperm quality or in vivo fertility outcomes of AI semen doses.

Melatonin administration to wild-type mice and nontreated NLRP3 mutant mice share similar inhibition of the inflammatory response during sepsis

The NLRP3 inflammasome is involved in the innate immune response during inflammation. Moreover, melatonin blunts the NF-κB/NLRP3 connection during sepsis. Thus, we compared the roles of the NLRP3 inflammasome and/or melatonin treatment in the septic response of wild-type and NLRP3^-/- mice. Mouse myocardial tissue was used for this purpose. The nuclear turnover of NF-κB was enhanced during sepsis, with an increase in TNFα, iNOS, and pro-IL-1β. The lack of inflammasome in NLRP3^-/- mice significantly reduced that response and blunted IL-1β maturation due to the lack of caspase-1. Clock and Bmal1 did not change in both mouse strains, enhancing Chrono expression in mutants. RORα, which positively regulates Bmal1, was enhanced at a similar extend in both mouse strains, whereas the expression of the Bmal1 repressor, Rev-Erbα, increased in WT but was depressed in NLRP3^-/- mice. Nampt, transcriptionally controlled by Bmal1, increased in WT mice together with Sirt1, whereas they remained unchanged in NLRP3^-/- mice. Melatonin treatment reduced the septic response in a comparable manner as did the lack of NLRP3, but unlike the latter, it normalized the clock genes turnover through the induction of RORα and repression of Rev-Erbα and Per2, leading to enhanced Nampt and Sirt1. The lack of NLRP3 inflammasome converts sepsis to a moderate inflammatory disease and identifies NLRP3 as a main target for the treatment of sepsis. The efficacy of melatonin in counteracting the NLRP3 inflammasome activation further confirms the indoleamine as a useful therapeutic drug against this serious condition.

Characterization of human pineal gland proteome

The pineal gland is a neuroendocrine gland located at the center of the brain. It is known to regulate various physiological functions in the body through secretion of the neurohormone melatonin. Comprehensive characterization of the human pineal gland proteome has not been undertaken to date. We employed a high-resolution mass spectrometry-based approach to characterize the proteome of the human pineal gland. A total of 5874 proteins were identified from the human pineal gland in this study. Of these, 5820 proteins were identified from the human pineal gland for the first time. Interestingly, 1136 proteins from the human pineal gland were found to contain a signal peptide domain, which indicates the secretory nature of these proteins. An unbiased global proteomic profile of this biomedically important organ should benefit molecular research to unravel the role of the pineal gland in neuropsychiatric and neurodegenerative diseases.

Melatonin Scavenger Properties against Oxidative and Nitrosative Stress: Impact on Gamete Handling and In Vitro Embryo Production in Humans and Other Mammals

Oxidative and nitrosative stress are common problems when handling gametes in vitro. In vitro development in mammalian embryos is highly affected by culture conditions, especially by reactive oxygen species (ROS) and reactive nitrogen species (RNS), because their absence or overproduction causes embryo arrest and changes in gene expression. Melatonin in gamete co-incubation during in vitro fertilization (IVF) has deleterious or positive effects, depending on the concentration used in the culture medium, demonstrating the delicate balance between antioxidant and pro-oxidant activity. Further research is needed to better understand the possible impact of melatonin on the different IVP steps in humans and other mammals, especially in seasonal breeds where this neuro-hormone system highly regulates its reproduction physiology.

Monitoring of libido and semen quality parameters in melatonin-treated French alpine bucks during the non-breeding season

The aim of this study was to investigate the effects of exogenous melatonin on libido and semen quality parameters in bucks during the non-breeding season. Twelve bucks of the French alpine breed from 1.5 to 4 years of age were assigned into melatonin (MG) and control (CG) groups, with 6 bucks in each group. The experimental period was 3 months (March-May), divided into six periods of 15 days each. The bucks in the MG group received four melatonin implants at the end of March. Two semen samples were taken from the bucks by artificial vagina once per week and their libido estimated. Volume and spermatozoa concentration, their mass motility and motility, proportion of live and total abnormal and forms with abnormal head and tail were determined in the obtained ejaculate samples. The total number of spermatozoa and functional spermatozoa fraction in the ejaculate was also calculated. The MG bucks had significantly higher mass motility and motility of spermatozoa in the first half of April, and a higher proportion of live spermatozoa in the first and second half of April (p < .05). Differences in libido intensity were not significant. The results indicated that the application of melatonin significantly improved the qualitative parameters of semen in bucks, as seen in increased mass motility, motility of spermatozoa and proportion of live spermatozoa shortly following melatonin insertion. Therefore, the results of the current study are novel regarding the use of melatonin treatment during the non-breeding season to improve the qualitative parameters of ejaculates in bucks.

Melatonin Promotes the In Vitro Development of Microinjected Pronuclear Mouse Embryos via Its Anti-Oxidative and Anti-Apoptotic Effects

CRISPR/Cas9 (Clustered regularly interspaced short palindromic repeats) combined with pronuclear microinjection has become the most effective method for producing transgenic animals. However, the relatively low embryo developmental rate limits its application. In the current study, it was observed that 10-7 M melatonin is considered an optimum concentration and significantly promoted the in vitro development of murine microinjected pronuclear embryos, as indicated by the increased blastocyst rate, hatching blastocyst rate and blastocyst cell number. When these blastocysts were implanted into recipient mice, the pregnancy rate and birth rate were significantly higher than those of the microinjected control, respectively. Mechanistic studies revealed that melatonin treatment reduced reactive oxygen species (ROS) production and cellular apoptosis during in vitro embryo development and improved the quality of the blastocysts. The implantation of quality-improved blastocysts led to elevated pregnancy and birth rates. In conclusion, the results revealed that the anti-oxidative and anti-apoptotic activities of melatonin improved the quality of microinjected pronuclear embryos and subsequently increased both the efficiency of embryo implantation and the birth rate of the pups. Therefore, the melatonin supplementation may provide a novel alternative method for generating large numbers of transgenic mice and this method can probably be used in human-assisted reproduction and genome editing.

Decreased melatonin levels and increased levels of advanced oxidation protein products in the seminal plasma are related to male infertility

Melatonin, an indolamine secreted by the pineal gland, is known as a powerful free-radical scavenger and wide-spectrum antioxidant. Therefore, the aim of this study was to correlate markers of oxidative protein damage (advanced oxidation protein products, AOPPs) and the total antioxidant capacity (TAC) with melatonin levels in the seminal plasma of men with azoospermia (n=37), theratozoospermia (n=29) and fertile controls (normozoospermia, n=37). Melatonin concentration was measured by radioimmunoassay. The levels of AOPP as well as TAC efficiency (determined by the ferric reducing antioxidant power, FRAP) were estimated by spectrophotometric methods. The concentration of melatonin and AOPP significantly differed in azoospermic (P<0.0001) and theratozoospermic (P<0.0001) patients versus fertile men, and correlated negatively (r=-0.33, P=0.0016). The TAC levels were significantly higher in azoospermia than in theratozoospermia (P=0.0022) and the control group (P=0.00016). In azoospermia, the AOPP concentration was also significantly higher than that observed in theratozoospermia (P=0.00029). Decreased levels of melatonin together with elevated AOPP altered the oxidative-antioxidative balance in the ejaculate, thereby reducing fertility. Therefore, melatonin and AOPP levels may serve as additional diagnostic markers of semen quality and male reproductive potential.

Melatonin levels in follicular fluid as markers for IVF outcomes and predicting ovarian reserve

Good-quality oocytes are critical for the success of in vitro fertilization (IVF), but, to date, there is no marker of ovarian reserve available that can accurately predict oocyte quality. Melatonin exerts its antioxidant actions as a strong radical scavenger that might affect oocyte quality directly as it is the most potent antioxidant in follicular fluid. To investigate the precise role of endogenous melatonin in IVF outcomes, we recruited 61 women undergoing treatment cycles of IVF or intracytoplasmic sperm injection (ICSI) procedures and classified them into three groups according to their response to ovarian stimulation. Follicular fluid was collected to assess melatonin levels using a direct RIA method. We found good correlations between melatonin levels in follicular fluid with age, anti-Müllerian hormone (AMH) and baseline follicle-stimulating hormone (bFSH), all of which have been used to predict ovarian reserve. Furthermore, as melatonin levels correlated to IVF outcomes, higher numbers of oocytes were collected from patients with higher melatonin levels and consequently the number of oocytes fertilized, zygotes cleaved, top quality embryos on D3, blastocysts obtained and embryos suitable for transplantation was higher. The blastocyst rate increased in concert with the melatonin levels across the gradient between the poor response group and the high response group. These results demonstrated that the melatonin levels in follicular fluid is associated with both the quantity and quality of oocytes and can predict IVF outcomes as well making them highly relevant biochemical markers of ovarian reserve.

Effects of melatonin in rats in the initial third stage of pregnancy exposed to sub-lethal doses of herbicides

Exposure to the herbicides Paraquat (PQ) and Roundup® may cause cell lesions due to an increase in oxidative stress levels in different biological systems, even in the reproductive system.

OBJECTIVE

Evaluate the possible changes in reproductive parameters and hepatic, as well as its prevention by simultaneous application of melatonin.

METHODS

Thirty-five female rats at the age of 3 months were divided into seven groups: three groups exposed to sub-lethal doses of the herbicides PQ (50mg/kg) and Roundup® (500mg/kg) (n=5, G2, G3 and G4); three groups exposed to herbicides and simultaneous treatment with 10mg/kg of Melatonin (n=5, G5, G6 and G7) and control group (n=5, G1) from the first to the seventh day of pregnancy. On the seventh day of pregnancy, the rats were anesthetized and euthanized, followed by laparotomy to remove their reproductive tissues and liver. Body and ovary weights were taken and the number of implantation sites, corpora lutea, preimplantation losses, implantation rates were counted and histopathology of the implantation sites, morphometry of the surface and glandular epithelia of endometrium and hepatic oxidative stress were undertaken.

RESULTS

The present study shows the decrease in body and ovary weight, decrease in the number of implantation sites, implantation rate, in the total number of corpora lutea and increase of preimplantation percentages were observed when compared to the G1: Fig. 1 and Table 1, (p>0.001 ANOVA/Tukey). The histopathological analysis of the implantation sites showed a disorder of the cytotrophoblast and cell degeneration within the blastocyst cavity in Fig. 4. Morphometry revealed a reduction in surface and glandular epithelia and in the diameter of the endometrial glands (Table 2; p>0.05 ANOVA/Tukey), whereas in liver, serum levels of thiobarbituric acid reactive substances (TBARS) were found to be significantly elevated (Fig. 2; p>0.001; p>0.05 ANOVA/Tukey), and serum level of reduced glutathione (GSH) was significantly lower (Fig. 3; p>0.001 ANOVA/Tukey). However, treatments with melatonin exhibited improvements in reproductive parameters, as well as reduced lesions in the implantation sites (Fig. 4.) and in serum levels TBARS (Fig. 2; p>0.001 ANOVA/Tukey), serum levels GSH (Fig. 3; p>0.001; p>0.05 ANOVA/Tukey).

CONCLUSIONS

These results reveal that melatonin is a protective agent against experimentally induced maternal/embryo toxicity with herbicides and favoring normalization of reproductive parameters and hepatic.

Potentiation of biological effects of mesenchymal stem cells in ischemic conditions by melatonin via upregulation of cellular prion protein expression

Mesenchymal stem cells (MSCs) are promising candidates for stem cell-based therapy in ischemic diseases. However, ischemic injury induces pathophysiological conditions, such as oxidative stress and inflammation, which diminish therapeutic efficacy of MSC-based therapy by reducing survival and functionality of transplanted MSCs. To overcome this problem, we explored the effects of melatonin on the proliferation, resistance to oxidative stress, and immunomodulatory properties of MSCs. Treatment with melatonin enhanced MSC proliferation and self-renewal via upregulation of cellular prion protein (PrP^C ) expression. Melatonin diminished the extent of MSC apoptosis in oxidative stress conditions by regulating the levels of apoptosis-associated proteins, such as BCL-2, BAX, PARP-1, and caspase-3, in a PrP^C -dependent manner. In addition, melatonin regulated the immunomodulatory effects of MSCs via the PrP^C -IDO axis. In a murine hind-limb ischemia model, melatonin-stimulated MSCs improved the blood flow perfusion, limb salvage, and vessel regeneration by lowering the extent of apoptosis of affected local cells and transplanted MSCs as well as by reducing infiltration of macrophages. These melatonin-mediated therapeutic effects were inhibited by silencing of PrP^C expression. Our findings for the first time indicate that melatonin promotes MSC functionality and enhances MSC-mediated neovascularization in ischemic tissues through the upregulation of PrP^C expression. In conclusion, melatonin-treated MSCs could provide a therapeutic strategy for vessel regeneration in ischemic disease, and the targeting of PrP^C levels may prove instrumental for MSC-based therapies.

Developmental Programming of Adult Disease: Reprogramming by Melatonin?

Adult-onset chronic non-communicable diseases (NCDs) can originate from early life through so-called the "developmental origins of health and disease" (DOHaD) or "developmental programming". The DOHaD concept offers the "reprogramming" strategy to shift the treatment from adulthood to early life, before clinical disease is apparent. Melatonin, an endogenous indoleamine produced by the pineal gland, has pleiotropic bioactivities those are beneficial in a variety of human diseases. Emerging evidence support that melatonin is closely inter-related to other proposed mechanisms contributing to the developmental programming of a variety of chronic NCDs. Recent animal studies have begun to unravel the multifunctional roles of melatonin in many experimental models of developmental programming. Even though some progress has been made in research on melatonin as a reprogramming strategy to prevent DOHaD-related NCDs, future human studies should aim at filling the translational gap between animal models and clinical trials. Here, we review several key themes on the reprogramming effects of melatonin in DOHaD research. We have particularly focused on the following areas: mechanisms of developmental programming; the interrelationship between melatonin and mechanisms underlying developmental programming; pathophysiological roles of melatonin in pregnancy and fetal development; and insight provided by animal models to support melatonin as a reprogramming therapy. Rates of NCDs are increasing faster than anticipated all over the world. Hence, there is an urgent need to understand reprogramming mechanisms of melatonin and to translate experimental research into clinical practice for halting a growing list of DOHaD-related NCDs.

Melatonin Is Involved in Regulation of Bermudagrass Growth and Development and Response to Low K+ Stress

Melatonin (N-acetyl-5-methoxytryptamine) plays critical roles in plant growth and development and during the response to multiple abiotic stresses. However, the roles of melatonin in plant response to K⁺ deficiency remain largely unknown. In the present study, we observed that the endogenous melatonin contents in bermudagrass were remarkably increased by low K⁺ (LK) treatment, suggesting that melatonin was involved in bermudagrass response to LK stress. Further phenotype analysis revealed that exogenous melatonin application conferred Bermudagrass enhanced tolerance to LK stress. Interestingly, exogenous melatonin application also promoted bermudagrass growth and development at normal condition. Furthermore, the K⁺ contents measurement revealed that melatonin-treated plants accumulated more K⁺ in both shoot (under both control and LK condition) and root tissues (under LK condition) compared with those of melatonin non-treated plants. Expression analysis indicated that the transcripts of K⁺ transport genes were significantly induced by exogenous melatonin treatment in bermudagrass under both control and LK stress conditions, especially under a combined treatment of LK stress and melatonin, which may increase accumulation of K⁺ content profoundly under LK stress and thereby contributed to the LK-tolerant phenotype. In addition, we investigated the role of melatonin in the regulation of photosystem II (PSII) activities under LK stress. The chlorophyll fluorescence transient (OJIP) curves were obviously higher in plants grown in LK with melatonin (LK+Mel) than those of plants grown in LK medium without melatonin application for 1 or 2 weeks, suggesting that melatonin plays important roles in PSII against LK stress. After a combined treatment of LK stress and melatonin, the values for performance indexes (PI_ABS, PI_Total, and PI_CS)_, flux ratios (φP₀, ΨE₀, and φE₀) and specific energy fluxes (ET_O/RC) were significantly improved compared with those of LK stress alone, suggesting that melatonin plays positive roles in protecting PSII activity under LK stress. Collectively, this study reveals an important role of melatonin in regulating bermudagrass response to LK stress.

IGFBP3 and MAPK/ERK signaling mediates melatonin-induced antitumor activity in prostate cancer

Treatment of prostate cancer (PCa), a leading cause of cancer among males, lacks successful strategies especially in advanced, hormone-refractory stages. Some clinical studies have shown an increase in neuroendocrine-like cells parallel to the tumor progression but their exact role is a matter of debate. The prostate is a well-known target for melatonin, which reduces PCa cells proliferation and induces neuroendocrine differentiation. To evaluate the mechanisms underlying the indole effects on neuroendocrine differentiation and its impact on PCa progression, we used a cell culture model (LNCaP) and a murine model (TRAMP). Persistent ERK1/2 activation was found in both, melatonin and androgen-deprived cells. Melatonin blocked nuclear translocation of androgen receptor (AR), thus confirming anti-androgenic actions of the indole. However, using a comparative genome microarray to check the differentially expressed genes in control, melatonin, or androgen-deprived cells, some differences were found, suggesting a more complex role of the indole. By comparing control cells with those treated with melatonin or depleted of androgen, a cluster of 26 differentially expressed genes (±2.5-fold) was found. Kallikreins (KLK)2 and KLK3 (PSA) were dramatically downregulated by both treatments whereas IGFBP3 and IGF1R were up- and downregulated, respectively, in both experimental groups, thus showing a role for IGF in both scenarios. Finally, melatonin prolonged the survival of TRAMP mice by 33% when given at the beginning or at advances stages of the tumor. Serum IGFBP3 was significantly elevated by the indole in early stages of the tumor, confirming in vivo the role of the IGF signaling in the oncostatic action of the indole.