The Angiotensin-melatonin axis

Accumulating evidence indicates that various biological and neuroendocrine circadian rhythms may be disrupted in cardiovascular and metabolic disorders. These circadian alterations may contribute to the progression of disease. Our studies direct to an important role of angiotensin II and melatonin in the modulation of circadian rhythms. The brain renin-angiotensin system (RAS) may modulate melatonin synthesis, a hormone with well-established roles in regulating circadian rhythms. Angiotensin production in the central nervous system may not only influence hypertension but also appears to affect the circadian rhythm of blood pressure. Drugs acting on RAS have been proven effective in the treatment of cardiovascular and metabolic disorders including hypertension and diabetes mellitus (DM). On the other hand, since melatonin is capable of ameliorating metabolic abnormalities in DM and insulin resistance, the beneficial effects of RAS blockade could be improved through combined RAS blocker and melatonin therapy. Contemporary research is evidencing the existence of specific clock genes forming central and peripheral clocks governing circadian rhythms. Further research on the interaction between these two neurohormones and the clock genes governing circadian clocks may progress our understanding on the pathophysiology of disease with possible impact on chronotherapeutic strategies

Melatonin action on luteal - granulosa cells in women with marital infertility undergoing in vitro fertilization

Introduction of the subject: Melatonin is a hormone related to the light-dark cycle and it plays an influential role in the reproductive system. In humans, researchers have shown there is three times more melatonin in follicular fluid than in the blood flow, suggesting the influence of the hormone on follicular maturation. However, little is known about melatonin action on granulosa cells in women with infertility, especially the molecular mechanisms involved. We are, therefore, conducting this study to evaluate melatonin action pathways in granulosa cells in the ovaries of women with infertility. To achieve our aim, we will use molecular biology, involving diverse signaling pathways, such as angiogenesis. Objective(s): to analyze melatonin action on luteal - granulosa cells in women with marital infertility undergoing in vitro fertilization. Methodology: For this, 68 patients, aged between 20 and 35 years, attended at the Human Reproduction Sector of the Federal University of São Paulo, were submitted to in vitro fertilization treatment. After all preparatory procedures were performed, luteal granulosa cells were removed and routed to the cell culture. The cells were divided into four groups: a) control; b) 0.1 μM melatonin; c) 1 μM melatonin; d) melatonin at 10μM. After a period of 10 days, the cells were trypsinized for extraction of the total RNA and later analysis of the gene expression by Real Time PCR of the angiogenesis signaling pathway. Results: Our data evaluated 96 genes, which are related to the angiogenesis pathway. The results of transcriptional expression showed important genes involved in this pathway that are hypo or hyperexpressed after treatment with melatonin. The main hyperexpressed genes were: fibroblast growth factor 1 (FGF1) genes; interleukin 1-beta (IL1B); receptor tyrosine kinase (VEGFR-2); folliculogenesis regulating genes (TGFB1). They act in the dynamics of follicular growth. On the other hand, the genes inducing factor 1-alpha (HIF1A), fibroblast growth factor 2 (FGF2), insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGFA) melatonin decreased its expression. Discussion and conclusion of the results: It is concluded that melatonin in high concentration (above 1 μM) may have dual function in increasing the expression of some growth factors and cytokines, in the decrease of other genes and mechanism of physiological compensation and also modulates negative angiogenesis, mainly in the dose (10 uM) of granulosa cells from women submitted to in vitro fertilization. Perhaps this fact is important for adequate follicular growth, avoiding excessive growth, which could turn the follicle into cyst, making ovulation difficult.Keywords: Melatonin; Granulosa cells; Women; Marital infertility; In vitro fertilization

Melatonin supplementation in the management of obesity and obesity-associated disorders: a review of physiological mechanisms and clinical applications

Despite the evolving advances in clinical approaches to obesity and its inherent comorbidities, the therapeutic challenge persists. Among several pharmacological tools already investigated, recent studies suggest that melatonin supplementation could be an efficient therapeutic approach in the context of obesity. In the present review, we have amalgamated the evidence so far available on physiological effects of melatonin supplementation in obesity therapies, addressing its effects upon neuroendocrine systems, cardiometabolic biomarkers and body composition. Most studies herein appraised employed melatonin supplementation at dosages ranging from 1 to 20 mg/day, and most studies followed up participants for periods from 3 weeks to 12 months. Overall, it was observed that melatonin plays an important role in glycaemic homeostasis, in addition to modulation of white adipose tissue activity and lipid metabolism, and mitochondrial activity. Additionally, melatonin increases brown adipose tissue volume and activity, and its antioxidant and anti-inflammatory properties have also been demonstrated. There appears to be a role for melatonin in adiposity reduction; however, several questions remain unanswered, for example melatonin baseline levels in obesity, and whether any seeming hypomelatonaemia or melatonin irresponsiveness could be clarifying factors. Supplementation dosage studies and more thorough clinical trials are needed to ascertain not only the relevance of such findings but also the efficacy of melatonin supplementation

Retroviral transfer of the p16INK4a cDNA inhibits C6 glioma formation in Wistar rats

BACKGROUND: The p16(INK4A) gene product halts cell proliferation by preventing phosphorylation of the Rb protein. The p16INK4a gene is often deleted in human glioblastoma multiforme, contributing to unchecked Rb phosphorylation and rapid cell division. We show here that transduction of the human p16INK4a cDNA using the pCL retroviral system is an efficient means of stopping the proliferation of the rat-derrived glioma cell line, C6, both in tissue culture and in an animal model. C6 cells were transduced with pCL retrovirus encoding the p16INK4a, p53, or Rb genes. These cells were analyzed by a colony formation assay. Expression of p16INK4a was confirmed by immunohistochemistry and Western blot analysis. The altered morphology of the p16-expressing cells was further characterized by the senescence-associated β-galactosidase assay. C6 cells infected ex vivo were implanted by stereotaxic injection in order to assess tumor formation. RESULTS: The p16INK4a gene arrested C6 cells more efficiently than either p53 or Rb. Continued studies with the p16INK4a gene revealed that a large portion of infected cells expressed the p16INK4a protein and the morphology of these cells was altered. The enlarged, flat, and bi-polar shape indicated a senescence-like state, confirmed by the senescence-associated β-galactosidase assay. The animal model revealed that cells infected with the pCLp16 virus did not form tumors. CONCLUSION: Our results show that retrovirus mediated transfer of p16INK4a halts glioma formation in a rat model. These results corroborate the idea that retrovirus-mediated transfer of the p16INK4a gene may be an effective means to arrest human glioma and glioblastoma

Melatonin and the cardiovascular system in animals: systematic review and meta-analysis

Melatonin, a hormone released by the pineal gland, demonstrates several effects on the cardiovascular system. Herein, we performed a systematic review and meta-analysis to verify the effects of melatonin in an experimental model of myocardial infarction. We performed a systematic review according to PRISMA recommendations and reviewed MEDLINE, Embase, and Cochrane databases. Only articles in English were considered. A systematic review of the literature published between November 2008 and June 2019 was performed. The meta-analysis was conducted using the RevMan 5.3 program provided by the Cochrane Collaboration. In total, 858 articles were identified, of which 13 were included in this review. The main results of this study revealed that melatonin benefits the cardiovascular system by reducing infarct size, improving cardiac function according to echocardiographic and hemodynamic analyses, affords antioxidant effects, improves the rate of apoptosis, decreases lactate dehydrogenase activity, enhances biometric analyses, and improves protein levels, as analyzed by western blotting and quantitative PCR. In the meta-analysis, we observed a statistically significant decrease in infarct size (mean difference [MD], -20.37 [-23.56, -17.18]), no statistical difference in systolic pressure (MD, -1.75 [-5.47, 1.97]), a statistically significant decrease in lactate dehydrogenase in animals in the melatonin group (MD, -4.61 [-6.83, -2.40]), and a statistically significant improvement in the cardiac ejection fraction (MD, -8.12 [-9.56, -6.69]). On analyzing potential bias, we observed that most studies presented a low risk of bias; two parameters were not included in the analysis, and one parameter had a high risk of bias. Melatonin exerts several effects on the cardiovascular system and could be a useful therapeutic target to combat various cardiovascular diseases

Melanopsin System Dysfunction in Smith-Magenis Syndrome Patients

PURPOSE: Smith-Magenis syndrome (SMS) causes sleep disturbance that is related to an abnormal melatonin profile. It is not clear how the genomic disorder leads to a disturbed synchronization of the sleep/wake rhythm in SMS patients. To evaluate the integrity of the intrinsically photosensitive retinal ganglion cell (ipRGC)/melanopsin system, the transducers of the light-inhibitory effect on pineal melatonin synthesis, we recorded pupillary light responses (PLR) in SMS patients. METHODS: Subjects were SMS patients (n = 5), with molecular diagnosis and melatonin levels measured for 24 hours and healthy controls (n = 4). Visual stimuli were 1-second red light flashes (640 nminsignificant direct ipRGC activation), followed by a 470-nm blue light, near the melanopsin peak absorption region (direct ipRGC activation). Blue flashes produce a sustained pupillary constriction (ipRGC driven) followed by baseline return, while red flashes produce faster recovery. RESULTS: Pupillary light responses to 640-nm red flash were normal in SMS patients. In response to 470-nm blue flash, SMS patients had altered sustained responses shown by faster recovery to baseline. SMS patients showed impairment in the expected melatonin production suppression during the day, confirming previous reports. CONCLUSIONS: SMS patients show dysfunction in the sustained component of the PLR to blue light. It could explain their well-known abnormal melatonin profile and elevated circulating melatonin levels during the day. Synchronization of daily melatonin profile and its photoinhibition are dependent on the activation of melanopsin. This retinal dysfunction might be related to a deficit in melanopsin-based photoreception, but a deficit in rod function is also possible.Sao Paulo Research Foundation (FAPESP) [2014/26818-2, 2014/50457-0, 2016/04538-3, 2014/06457-5, 2015/22227-2, 2016/22007-5]National Council for Scientific and Technological Development (CNPq) [480428/2013-4, 470785/2014-4, 404239/2016-1]CAPES [3263/2013]Janos Bolyai Scholarship of the Hungarian Academy of SciencesUniv Sao Paulo, Dept Expt Psychol, Inst Psychol, Sao Paulo, BrazilSemmelweis Univ, Dept Ophthalmol, Budapest, HungaryUniv Sao Paulo, Dept Neurol, Fac Med, Sao Paulo, BrazilBudapest Univ Technol & Econ, Dept Mechatron Opt & Engn Informat, Budapest, HungaryUniv Texas San Antonio, Dept Cellular & Struct Biol, San Antonio, TX USAUniv Fed Sao Paulo, Dept Physiol, Sao Paulo, BrazilUniv Sao Paulo, Dept Physiol & Biophys, Inst Biomed Sci, Av Lineu Prestes 1524, BR-05508000 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Physiol, Sao Paulo, BrazilFAPESP [2014/26818-2, 2014/50457-0, 2016/04538-3, 2014/06457-5, 2015/22227-2, 2016/22007-5]CNPq [480428/2013-4, 470785/2014-4, 404239/2016-1]CAPES [3263/2013]Web of Scienc

Developmental and light-entrained expression of melatonin and its relationship to the circadian clock in the sea anemone Nematostella vectensis

Background: The primary hormone of the vertebrate pineal gland, melatonin, has been identified broadly throughout the eukaryotes. While the role for melatonin in cyclic behavior via interactions with the circadian clock has only been reported in vertebrates, comparative research has shown that the transcription-translation loops of the animal circadian clock likely date to the cnidarian-bilaterian ancestor, leaving open significant questions about the evolutionary origin of melatonin signaling in circadian behavior by interacting with the molecular clock.\ud Results: Expression of melatonin in adult anemones showed peak expression at the end of light period (zeitgeber time (ZT) = 12) when cultured under diel conditions, coinciding with expression of genes and enzyme activity for members of the melatonin synthesis pathway (tryptophan hydroxylase and hydroxyindol-O-methyltransferase), which also showed rhythmic expression. During embryogenesis and juvenile stages, melatonin showed cyclic oscillations in concentration, peaking in midday. Spatial (in situ hybridization) and quantitative (real-time PCR) transcription of clock genes during development of N. vectensis showed these ‘clock’ genes are expressed early in\ud the development, prior to rhythmic oscillations, suggesting functions independent of a function in the circadian clock. Finally, time-course studies revealed that animals transferred from diel conditions to constant darkness lose circadian expression for most of the clock genes within 4 days, which can be reset by melatonin supplementation.\ud Conclusions: Our results support an ancient role for melatonin in the circadian behavior of animals by showing cyclic expression of this hormone under diel conditions, light-dependent oscillations in genes in the melatonin synthesis pathway, and the function of melatonin in initiating expression of circadian clock genes in the cnidarian N. vectensis. The differences in expression melatonin and the circadian clock gene network in the adult stage when compared with developmental stages of N. vectensis suggests new research directions to characterize stage-specific mechanisms of circadian clock function in animals.São Paulo State Research Foundation (FAPESP)National Council for Scientific and Technological Development (CNPq)Coordination for the Improvement of Higher Level Personnel (CAPES