Showing papers in "Journal of Pineal Research in 2011"
TL;DR: In this article, a review summarizes the current progress in understanding the physicochemical insights related to the free radical-scavenging activity of melatonin and concludes that melatonin efficiently protects against oxidative stress by a variety of mechanisms.
Abstract: Oxidative stress has been proven to be related to the onset of a large number of health disorders. This chemical stress is triggered by an excess of free radicals, which are generated in cells because of a wide variety of exogenous and endogenous processes. Therefore, finding strategies for efficiently detoxifying free radicals has become a subject of a great interest, from both an academic and practical points of view. Melatonin is a ubiquitous and versatile molecule that exhibits most of the desirable characteristics of a good antioxidant. The amount of data gathered so far regarding the protective action of melatonin against oxidative stress is overwhelming. However, rather little is known concerning the chemical mechanisms involved in this activity. This review summarizes the current progress in understanding the physicochemical insights related to the free radical-scavenging activity of melatonin. Thus far, there is a general agreement that electron transfer and hydrogen transfer are the main mechanisms involved in the reactions of melatonin with free radicals. However, the relative importance of other mechanisms is also analyzed. The chemical nature of the reacting free radical also has an influence on the relative importance of the different mechanisms of these reactions. Therefore, this point has also been discussed in detail in the current review. Based on the available data, it is concluded that melatonin efficiently protects against oxidative stress by a variety of mechanisms. Moreover, it is proposed that even though it has been referred to as the chemical expression of darkness, perhaps it could also be referred to as the chemical light of health.
992 citations
TL;DR: A remnant silhouette of premortem dynamics within the hormone’s biosynthesis pathway can be constructed and protein‐protein interactions and nucleo‐cytoplasmic protein shuttling indicate furthermore a novel twist in the molecular dynamics in the cells of this neuroendocrine brain structure.
Abstract: The human pineal gland is a neuroendocrine transducer that forms an integral part of the brain. Through the nocturnally elevated synthesis and release of the neurohormone melatonin, the pineal gland encodes and disseminates information on circadian time, thus coupling the outside world to the biochemical and physiological internal demands of the body. Approaches to better understand molecular details behind the rhythmic signalling in the human pineal gland are limited but implicitly warranted, as human chronobiological dysfunctions are often associated with alterations in melatonin synthesis. Current knowledge on melatonin synthesis in the human pineal gland is based on minimally invasive analyses, and by the comparison of signalling events between different vertebrate species, with emphasis put on data acquired in sheep and other primates. Together with investigations using autoptic pineal tissue, a remnant silhouette of premortem dynamics within the hormone's biosynthesis pathway can be constructed. The detected biochemical scenario behind the generation of dynamics in melatonin synthesis positions the human pineal gland surprisingly isolated. In this neuroendocrine brain structure, protein-protein interactions and nucleo-cytoplasmic protein shuttling indicate furthermore a novel twist in the molecular dynamics in the cells of this neuroendocrine brain structure. These findings have to be seen in the light that an impaired melatonin synthesis is observed in elderly and/or demented patients, in individuals affected by Alzheimer's disease, Smith-Magenis syndrome, autism spectrum disorder and sleep phase disorders. Already, recent advances in understanding signalling dynamics in the human pineal gland have significantly helped to counteract chronobiological dysfunctions through a proper restoration of the nocturnal melatonin surge.
354 citations
TL;DR: Melatonin therapy may be of benefit for patients with MS, particularly with arterial hypertension, and further studies with higher doses of melatonin or prolonged supplementation are awaited.
Abstract: Experimental studies have proven that melatonin has many beneficial pleiotropic actions. The aim of this study was to assess melatonin efficacy in patients with metabolic syndrome (MS). The study included 33 healthy volunteers (who were not treated with melatonin) and 30 patients with MS, who did not respond to 3-month lifestyle modification. Patients with MS were treated with melatonin (5 mg/day, 2 hr before bedtime) for 2 months. The following parameters were studied: systolic and diastolic blood pressure (SBP, DBP), levels of glucose, serum lipids, C-reactive protein, fibrinogen, activities of antioxidative enzymes: catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), thiobarbituric acid reactive substrates (TBARS). After 2-month therapy in comparison with baseline, the following significant changes were measured: systolic blood pressure (132.8±9.8 versus 120.5±11.0 mmHg, P<0.001), DBP (81.7±8.8 versus 75±7.4 mmHg, P<0.01), low-density lipoprotein cholesterol (LDL-C) (149.7±26.4 versus 139.9±30.2 mg/dL, P<0.05), TBARS (0.5±0.2 versus 0.4±0.1 μm/gHb, P<0.01), and CAT (245.9±46.9 versus 276.8±39.4 U/gHb). Melatonin administered for 2 months significantly improved antioxidative defense (increase in CAT activity, decrease in TBARS level) and lipid profile (decrease in LDL-C), and lowered blood pressure. We conclude that melatonin therapy may be of benefit for patients with MS, particularly with arterial hypertension. Further studies with higher doses of melatonin or prolonged supplementation are awaited.
259 citations
TL;DR: It is demonstrated that melatonin promotes osteoblastic differentiation and mineralization in MC3T3‐E1 cells via the BMP/ERK/Wnt pathways.
Abstract: Although melatonin has a variety of biological actions such as antitumor, antiangiogenic, and antioxidant activities, the osteogenic mechanism of melatonin still remains unclear. Thus, in the present study, the molecular mechanism of melatonin was elucidated in the differentiation of mouse osteoblastic MC3T3-E1 cells. Melatonin enhanced osteoblastic differentiation and mineralization compared to untreated controls in preosteoblastic MC3T3-E1 cells. Also, melatonin increased wound healing and dose-dependently activated osteogenesis markers such as runt-related transcription factor 2 (Runx2), osteocalcin (OCN), bone morphogenic protein (BMP)-2 and -4 in MC3T3-E1 cells. Of note, melatonin activated Wnt 5 α/β, β-catenin and the phosphorylation of c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) in a time-dependent manner while it attenuated phosphorylation of glycogen synthase kinase 3 beta (GSK-3β) in MC3T3-E1 cells. Consistently, confocal microscope observation revealed that BMP inhibitor Noggin blocked melatonin-induced nuclear localization of β-catenin. Furthermore, Western blotting showed that Noggin reversed activation of β-catenin and Wnt5 α/β and suppression of GSK-3β induced by melatonin in MC3T3-E1 cells, which was similarly induced by ERK inhibitor PD98059. Overall, these findings demonstrate that melatonin promotes osteoblastic differentiation and mineralization in MC3T3-E1 cells via the BMP/ERK/Wnt pathways.
177 citations
TL;DR: In this paper, the authors reviewed the current evidence regarding the analgesic properties of melatonin in animals and humans with chronic pain and concluded that the effects may be linked to G(i) -coupled melatonin receptors with unknown downstream changes with a consequential reduction in anxiety and pain.
Abstract: Melatonin is an endogenous indoleamine, produced mainly by the pineal gland. Melatonin has been proven to have chronobiotic, antioxidant, antihypertensive, anxiolytic and sedative properties. There are also experimental and clinical data supporting an analgesic role of melatonin. In experimental studies, melatonin shows potent analgesic effects in a dose-dependent manner. In clinical studies, melatonin has been shown to have analgesic benefits in patients with chronic pain (fibromyalgia, irritable bowel syndrome, migraine). The physiologic mechanism underlying the analgesic actions of melatonin has not been clarified. The effects may be linked to G(i) -coupled melatonin receptors, to G(i) -coupled opioid μ-receptors or GABA-B receptors with unknown downstream changes with a consequential reduction in anxiety and pain. Also, the repeated administration of melatonin improves sleep and thereby may reduce anxiety, which leads to lower levels of pain. In this paper, we review the current evidence regarding the analgesic properties of melatonin in animals and humans with chronic pain.
160 citations
TL;DR: Mitochondrial dysfunction is a hallmark of Alzheimer’s disease (AD) and is observed in mutant amyloid precursor protein (APP) transgenic mouse models of familial AD, and treatments that stimulate melatonin receptor signaling may be beneficial for restoring mitochondrial function in AD.
Abstract: Mitochondrial dysfunction is a hallmark of Alzheimer's disease (AD) and is observed in mutant amyloid precursor protein (APP) transgenic mouse models of familial AD. Melatonin is a potent antioxidant, can prevent toxic aggregation of Alzheimer's beta-amyloid (Aβ) peptide and, when taken long term, can protect against cognitive deficits in APP transgenic mice. To study the effects of melatonin on brain mitochondrial function in an AD model, APP/PS1 transgenic mice were treated for 1 month with melatonin. Analysis of isolated brain mitochondria from mice indicated that melatonin treatment decreased mitochondrial Aβ levels by two- to fourfold in different brain regions. This was accompanied by a near complete restoration of mitochondrial respiratory rates, membrane potential, and ATP levels in isolated mitochondria from the hippocampus, cortex, or striatum. When isolated mitochondria from untreated young mice were given melatonin, a slight increase in respiratory rate was observed. No such effect was observed in mitochondria from aged mice. In APP-expressing neuroblastoma cells in culture, mitochondrial function was restored by melatonin or by the structurally related compounds indole-3-propionic acid or N(1)-acetyl-N(2)-formyl-5-methoxykynuramine. This restoration was partially blocked by melatonin receptor antagonists indicating melatonin receptor signaling is required for the full effect. Therefore, treatments that stimulate melatonin receptor signaling may be beneficial for restoring mitochondrial function in AD, and preservation of mitochondrial function may an important mechanism by which long term melatonin treatment delays cognitive dysfunction in AD mice.
152 citations
TL;DR: A review article as mentioned in this paper discusses recent work on the melatonin-mediated circadian regulation and integration of molecular, dietary, and metabolic signaling mechanisms involved in human breast cancer growth and the consequences of circadian disruption by exposure to light at night (LAN).
Abstract: This review article discusses recent work on the melatonin-mediated circadian regulation and integration of molecular, dietary, and metabolic signaling mechanisms involved in human breast cancer growth and the consequences of circadian disruption by exposure to light at night (LAN). The antiproliferative effects of the circadian melatonin signal are mediated through a major mechanism involving the activation of MT(1) melatonin receptors expressed in human breast cancer cell lines and xenografts. In estrogen receptor (ERα+) human breast cancer cells, melatonin suppresses both ERα mRNA expression and estrogen-induced transcriptional activity of the ERα via MT(1) -induced activation of G(αi2) signaling and reduction of 3',5'-cyclic adenosine monophosphate (cAMP) levels. Melatonin also regulates the transactivation of additional members of the steroid hormone/nuclear receptor super-family, enzymes involved in estrogen metabolism, expression/activation of telomerase, and the expression of core clock and clock-related genes. The anti-invasive/anti-metastatic actions of melatonin involve the blockade of p38 phosphorylation and the expression of matrix metalloproteinases. Melatonin also inhibits the growth of human breast cancer xenografts via another critical pathway involving MT(1) -mediated suppression of cAMP leading to blockade of linoleic acid uptake and its metabolism to the mitogenic signaling molecule 13-hydroxyoctadecadienoic acid (13-HODE). Down-regulation of 13-HODE reduces the activation of growth factor pathways supporting cell proliferation and survival. Experimental evidence in rats and humans indicating that LAN-induced circadian disruption of the nocturnal melatonin signal activates human breast cancer growth, metabolism, and signaling provides the strongest mechanistic support, thus far, for population and ecological studies demonstrating elevated breast cancer risk in night shift workers and other individuals increasingly exposed to LAN.
149 citations
TL;DR: The hydroxyl radical was found to be the unique species able to initiate the oxidation of melatonin, leading to three main products, e.g. AFMK, N1‐acetyl‐N2‐formyl‐5‐methoxykynurenin (AMK) and hydroxymelatonin (HO‐MLT).
Abstract: Melatonin (N-acetyl-5-hydroxytryptamine) is a pineal hormone widely known for its antioxidant properties, both in vivo and by direct capture of free radicals in vitro. Although some metabolites and oxidation products of melatonin have been identified, the molecular mechanism by which melatonin exerts its antioxidant properties has not been totally unravelled. This study investigated the reaction mechanism of oxidation of melatonin by radio-induced reactive oxygen species, generated by gamma radiolysis of water for aqueous solutions of melatonin (from 20 to 200 μm), in the presence or absence of molecular oxygen. The hydroxyl radical was found to be the unique species able to initiate the oxidation process, leading to three main products, e.g. N(1)-acetyl-N(2)-formyl-5-methoxykynurenin (AFMK), N(1)-acetyl-5-methoxykynurenin (AMK) and hydroxymelatonin (HO-MLT). The generation of AFMK and HO-MLT strongly depended on the presence of molecular oxygen in solution: AFMK was the major product in aerated solutions (84%), whereas HO-MLT was favoured in the absence of oxygen (86%). Concentrations of AMK remained quite low, and AMK was proposed to result from a chemical hydrolysis of AFMK in solution. A K-value of 1.1 × 10(-4) was calculated for this equilibrium. Both hydrogen peroxide and superoxide dismutase had no effect on the radio-induced oxidation of melatonin, in good accordance for the second case with the poor reactivity of the superoxide anion towards melatonin. Finally, a reaction mechanism was proposed for the oxidation of melatonin in vitro.
147 citations
TL;DR: Induction patterns of ASMT mRNA were well matched with the production of melatonin in rice leaves during senescence, as well as several stressors, and ASMT enzyme activity was inhibited by various related compounds.
Abstract: N-acetylserotonin methyltransferase (ASMT), the last enzyme in the synthesis of melatonin, catalyzes N-acetylserotonin into melatonin. For the first time, we cloned ASMT from rice through the analysis of recombinant Escherichia coli harboring putative rice O-methyltransferase (OMT) cDNAs. In total, 18 full-length cDNAs, which show homology to wheat caffeic acid 3-O-methyltransferase, were expressed in E. coli and induced in the presence of N-acetylserotonin; we then analyzed the production of melatonin. Only recombinant E. coli line 15 showed melatonin synthesis; no other recombinant lines produced melatonin with the addition of N-acetylserotonin in E. coli culture. Line 15 clearly exhibited in vitro ASMT enzyme activity with 0.27 pkat/mg protein. ASMT enzyme activity was inhibited by various related compounds such as N-acetyltryptamine and N-acetyltyrosine. The open reading frame of ASMT consists of 364 amino acids possessing well-conserved motifs found in plant OMT such as S-adenosyl-L-methionine-binding and catalytic sites. Induction patterns of ASMT mRNA were well matched with the production of melatonin in rice leaves during senescence, as well as several stressors.
144 citations
TL;DR: The addition of melatonin to ram semen freezing extender protected spermatozoa during cryopreservation in a dose‐dependent manner and is likely to be mediated by its well‐known antioxidant properties, even if a direct action of the indolamine cannot be ruled out.
Abstract: Cryopreservation harms spermatozoa at different levels and thus impairs their fertilizing ability. The role of melatonin in protecting spermatozoa from different kind injuries has been widely reported. Thus, this study tested whether the addition of melatonin to ram semen freezing extender could exert a protective effect and ameliorate postthawing sperm function. Melatonin was added to recommended ram extender to yield five different final concentrations: 0.001, 0.01, 0.1, 1, and 10 mm. A control group without melatonin supplementation was included. Spermatozoa viability, motility parameters, and intracellular ATP concentrations were evaluated both before and after cryopreservation, while DNA integrity and in vitro fertilizing ability were evaluated only after thawing. Obtained results showed that the concentration of 1 mm melatonin led to higher viability rates, higher percentages of total motile and progressive motile spermatozoa, higher percentages of spermatozoa with average rapid and medium velocity, higher intracellular ATP concentrations, and higher DNA integrity among semen frozen in control and melatonin-supplemented extenders (P<0.05). In addition, results obtained after the IVF test showed that at 1 mm concentration, melatonin led to a faster first embryonic division and to higher total cleavage rates compared to the other experimental groups (P<0.05). No difference in embryo output was observed among the six experimental groups. In conclusion, the addition of melatonin to ram semen freezing extender protected spermatozoa during cryopreservation in a dose-dependent manner. These results are likely to be mediated by its well-known antioxidant properties, even if a direct action of the indolamine cannot be ruled out.
140 citations
TL;DR: It is suggested that melatonin ameliorates I/R‐induced liver damage by modulation of TLR‐mediated inflammatory responses.
Abstract: This study investigated the immunomodulating effect of melatonin on toll-like receptor (TLR)-stimulated signal transduction. Rats were subjected to 60 min of ischemia followed by 1 or 5 hr of reperfusion. Melatonin (10 mg/kg) or the vehicle was administered intraperitoneally 15 min prior to ischemia and immediately before reperfusion. Melatonin treatment significantly reduced the level of serum alanine aminotransferase activity. Increased levels of TLR3 and TLR4 protein expression induced by ischemia/reperfusion (I/R) were attenuated by melatonin. Serum level of high-mobility group box 1 (HMGB1), a potent alarmin of the TLR system, increased significantly in the I/R group, and melatonin inhibited this release. Melatonin suppressed the increase in myeloid differentiation factor 88 (MyD88) protein expression, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) phosphorylation and nuclear translocation of nuclear factor j B( NF-jB) and phosphorylated c-Jun, a component of activator protein 1. The increased level of toll-receptor- associated activator of interferon (TRIF) expression, phosphorylation of interferon (IFN) regulatory factor 3 (IRF3) and serum IFN-b was attenuated by melatonin. Melatonin attenuated the levels of tumor necrosis factor alpha (TNF-a), interleukin (IL)-6 and inducible nitric oxide synthase (iNOS) protein and mRNA expression, while the level of heme oxygenase-1 (HO-1) was augmented. Our results suggest that melatonin ameliorates I/R-induced liver damage by modulation of TLR-mediated inflammatory responses.
TL;DR: Observations provide new evidence of the antioxidant/anti‐stress function of melatonin, and it is the first report of its potential application in the preservation of elite endangered germplasm through the process of cryopreservation.
Abstract: An important aspect of the function of melatonin seems to be the mediation of stress caused by environmental and chemical factors. In the cryopreservation process, environmental changes including osmotic injury, desiccation, and low temperature can impose a series of stresses on plants. In this study, we evaluated the role of melatonin in stress protection during the process of cryopreservation using callus of an endangered plant species Rhodiola crenulata. The survival rate of the cryopreserved callus significantly increased when the callus was pretreated for 5 days with 0.1 mu m melatonin prior to freezing in liquid nitrogen. Analysis of antioxidative activity following the pretreatment of callus with 0.1 mu m melatonin showed a significant reduction in malondialdehyde production during various steps of cryopreservation. Enhanced peroxidase and catalase activity was observed in the callus after pretreatment with 0.1 mu m melatonin compared to the control. These observations provide new evidence of the antioxidant/anti-stress function of melatonin, and it is the first report of its potential application in the preservation of elite endangered germplasm through the process of cryopreservation.
TL;DR: It is shown for the first time that melatonin levels fluctuate during the day/night cycle in plants grown under field conditions in a fruit organ of the species Vitis vinifera, and it is determined that the diurnal decay of melatonin in berry skins is induced by sunlight.
Abstract: The identification of melatonin in plants has inspired new investigations to understand its biological function and which endogenous and external factors control its levels in these organisms. Owing to the therapeutical and nutraceutical properties of melatonin, it should be important to develop reliable analytical methods for its quantification in vegetal matrices containing this indoleamine, such as grape and wine. The main objectives of the present study were to test whether melatonin levels fluctuate during the day in berry skins of Vitis vinifera L. cv Malbec, thereby possibly relating its abundance to its putative antioxidant function, to determine whether daylight reaching clusters negatively controls melatonin levels, and to evaluate whether total polyphenols and anthocyanins also change through a 24-hr period. Grapes were harvested throughout the day/night to determine the moment when high levels of these components are present in grapes. The presence of melatonin in grapes was evaluated by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry. It is shown for the first time that melatonin levels fluctuate during the day/night cycle in plants grown under field conditions in a fruit organ of the species Vitis vinifera. We also determined that the diurnal decay of melatonin in berry skins is induced by sunlight, because covered bunches retained higher melatonin levels than exposed ones, thus explaining at least part of the basis of its daily fluctuation. Evidence of melatonin's antioxidant role in grapes is also suggested by monitoring malondialdehyde levels during the day.
TL;DR: It is shown that the entire population of cells expressing DCX is increased after 14 days of treatment with melatonin, which might open the opportunity of using melatonin as an adjuvant in attempts to extrinsically stimulate adult hippocampal neurogenesis in neuropsychiatric disease, dementia or cognitive ageing.
Abstract: In the course of adult hippocampal neurogenesis, the postmitotic maturation and survival phase is associated with dendrite maturation. Melatonin modulates the survival of new neurons with relative specificity. During this phase, the new neurons express microtubule-associated protein doublecortin (DCX). Here, we show that the entire population of cells expressing DCX is increased after 14 days of treatment with melatonin. As melatonin also affects microtubule polymerization which is important for neuritogenesis and dendritogenesis, we studied the consequences of chronic melatonin administration on dendrite maturation of DCX-positive cells. Treatment with melatonin increased the number of DCX-positive immature neurons with more complex dendrites. Sholl analysis revealed that melatonin treatment lead to greater complexity of the dendritic tree. In addition, melatonin increased the total volume of the granular cell layer. Besides its survival-promoting effect, melatonin thus also increases dendritic maturation in adult neurogenesis. This might open the opportunity of using melatonin as an adjuvant in attempts to extrinsically stimulate adult hippocampal neurogenesis in neuropsychiatric disease, dementia or cognitive ageing.
TL;DR: Administration of melatonin, alone or in a combination with fluoxetine, was effective in the treatment of patients with FMS.
Abstract: Fibromyalgia syndrome (FMS) is a chronic musculoskeletal disorder characterized by generalized muscular pain accompanied by fatigue and tenderness at specific anatomic sites called tender points. Although preliminary evidence indicates that melatonin may be effective in treating the pain associated with FMS, no definitive evidence supports this claim. This study was designed to evaluate the significance of using different doses of melatonin, alone or in combination with fluoxetine for the management of FMS. A double-blind, placebo-controlled clinical study was performed on 101 patients (95 women and 6 men) who fulfilled the criteria of the American College of Rheumatology (ACR) of FMS. The patients were randomized into four groups: group A (24 patients) treated with 20 mg/day fluoxetine alone; group B (27 patients) treated with melatonin 5 mg alone; group C (27 patients) treated with 20 mg fluoxetine plus 3 mg melatonin; group D (23 patients) treated with 20 mg fluoxetine plus 5 mg melatonin. Both drugs were given once daily in the morning and night time, respectively, for 8 wk. Each patient was clinically evaluated through direct interview with the patients using the Fibromyalgia Impact Questionnaire (FIQ) at zero time and after 8 wk. Using melatonin (3 mg or 5 mg/day) in combination with 20 mg/day fluoxetine resulted in significant reduction in both total and different components of FIQ score compared to the pretreatment values. In conclusion, administration of melatonin, alone or in a combination with fluoxetine, was effective in the treatment of patients with FMS.
TL;DR: Melatonin and resveratrol, as found in red wine, protect the heart in an experimental model of myocardial infarction via the SAFE pathway.
Abstract: Epidemiological studies suggest that regular moderate consumption of red wine confers cardioprotection but the mechanisms involved in this effect remain unclear. Recent studies demonstrate the presence of melatonin in wine. We propose that melatonin, at a concentration found in red wine, confers cardioprotection against ischemia–reperfusion injury. Furthermore, we investigated whether both melatonin and resveratrol protect via the activation of the newly discovered survivor activating factor enhancement (SAFE) prosurvival signaling pathway that involves the activation of tumor necrosis factor alpha (TNFα) and the signal transducer and activator of transcription 3 (STAT3). Isolated perfused male mouse (wild type, TNFα receptor 2 knockout mice, and cardiomyocyte-specific STAT3-deficient mice) or rat hearts (Wistars) were subjected to ischemia–reperfusion. Resveratrol (2.3 mg/L) or melatonin (75 ng/L) was perfused for 15 min with a 10-min washout period prior to an ischemia–reperfusion insult. Infarct size was measured at the end of the protocol, and Western blot analysis was performed to evaluate STAT3 activation prior to the ischemic insult. Both resveratrol and melatonin, at concentrations found in red wine, significantly reduced infarct size compared with control hearts in wild-type mouse hearts (25 ± 3% and 25 ± 3% respectively versus control 69 ± 3%, P < 0.001) but failed to protect in TNF receptor 2 knockout or STAT3-deficient mice. Furthermore, perfusion with either melatonin or resveratrol increased STAT3 phosphorylation prior to ischemia by 79% and 50%, respectively (P < 0.001 versus control). Our data demonstrate that both melatonin and resveratrol, as found in red wine, protect the heart in an experimental model of myocardial infarction via the SAFE pathway.
TL;DR: Melatonin is a useful tool to improve the quality of stored stallion sperm, increasing their life span and reducing premature aging, this likely relates to melatonin’s antioxidant properties.
Abstract: Lipid peroxidation (LPO) has been claimed as a major factor involved in stallion damage during storage or cryopreservation. Because melatonin is a well-known potent antioxidant, the aim of the present study was to investigate the effect of melatonin during in vitro incubation. Furthermore, we investigated the presence of specific melatonin receptors (MT1 and MT2) using specific polyclonal antibodies and western blotting. Stallion spermatozoa were incubated up to 3 hr at 37°C in the presence of different concentrations of melatonin (0, 50 pm, 100 pm, 200 pm, or 1 μm). At the beginning and at the end of the incubation period, sperm motility (using computer-assisted sperm analysis), membrane integrity and permeability, fluidity of the sperm membrane, LPO, and mitochondrial membrane potential (Δψm) were flow cytometrically evaluated. Melatonin reduced changes in the spermatozoa related to apoptosis (increased sperm membrane permeability and lowered Δψm) (P < 0.05). Furthermore, LPO was dramatically reduced (P < 0.01) while no effect was observed on sperm motility or kinematics. Interestingly, melatonin helped maintain a more fluid sperm plasmalemma (P < 0.05). Our results clearly show the absence of MT1 and MT2 receptors in the stallion spermatozoa. It is concluded that melatonin is a useful tool to improve the quality of stored stallion sperm, increasing their life span and reducing premature aging, this likely relates to melatonin's antioxidant properties.
TL;DR: Experimental data suggest that melatonin decreases inflammatory changes after major liver resection, thus positively influencing the postoperative course, and a single preoperative enteral dose of melatonin is effectively absorbed and is safe and well tolerated in patients undergoing major liver surgery.
Abstract: Experimental data suggest that melatonin decreases inflammatory changes after major liver resection, thus positively influencing the postoperative course. To assess the safety of a preoperative single dose of melatonin in patients undergoing major liver resection, a randomized controlled double-blind pilot clinical trial with two parallel study arms was designed at the Department of General and Transplantation Surgery, Ruprecht-Karls-University, Heidelberg. A total of 307 patients, who were referred for liver surgery, were screened. One hundred and thirteen patients, for whom a major liver resection (≥3 segments) was scheduled, were eligible. Sixty-three eligible patients refused to participate, and therefore, 50 patients were randomized. A preoperative single dose of melatonin (50 mg/kg BW) dissolved in 250 mL of milk was administered through the gastric tube after the intubation for general anesthesia. Controls were given the same amount of microcrystalline cellulose. Primary endpoint was safety. Secondary endpoints were postoperative complications. Melatonin was effectively absorbed with serum concentrations of 1142.8 ± 7.2 ng/mL (mean ± S.E.M.) versus 0.3 ± 7.8 ng/mL in controls (P < 0.0001). Melatonin treatment resulted in lower postoperative transaminases over the study period (P = 0.6). There was no serious adverse event in patients after melatonin treatment. A total of three infectious complications occurred in either group. A total of eight noninfectious complications occurred in five control patients, whereas three noninfectious complications occurred in three patients receiving preoperative melatonin (P = 0.3). There was a trend toward shorter ICU stay and total hospital stay after melatonin treatment. Therefore, a single preoperative enteral dose of melatonin is effectively absorbed and is safe and well tolerated in patients undergoing major liver surgery.
TL;DR: The effect of melatonin on AMPK and the impact of this effect on IBD and colon cancer remains an open question as discussed by the authors, and there is no information about whether antitumoral effects of Melatonin on colon cancer are dependent on autophagy.
Abstract: In intestinal bowel disease (IBD), immune-mediated conditions exert their effects through various cells and proinflammatory mediators. Recent data support a participation of the endoplasmic reticulum stress and mitochondrial dysfunctions in IBD. Moreover, it is evident that chronic degenerative pathologies, including IBD, share comparable disease mechanisms with alteration in the autophagy mechanisms. Chronic inflammation in IBD exposes these patients to a number of signals known to have tumorigenic effects. This circuitry of inflammation and cancer modifies apoptosis and autophagy, and promotes cellular cycle progression, invasion, and angiogenesis. Melatonin has been shown as a specific antioxidant reducing oxidative damage in both lipid and aqueous cell environments. However, several studies provide further insight into the molecular mechanisms of melatonin action in the colon. In this line, recent data suggest that melatonin modulates autophagy and sirtuin activity. An anti-autophagic property of melatonin has been demonstrated, and it could contribute to its anti-oncogenic activity. Nevertheless, there is no information about whether antitumoral effects of melatonin on colon cancer are dependent on autophagy. Sirtuins have pleiotropic effects on cancer development, being reported both as facilitator and as suppressor of colon cancer development. Sirtuins and melatonin are connected through the circadian clock machinery, and melatonin seems able to correct the alterations in sirtuin activity associated with several pathological conditions. Autophagy and sirtuin activities are linked through 5'AMP-activated protein kinase (AMPK) activation, which switches on autophagy and increases sirtuin. The effect of melatonin on AMPK and the impact of this effect on IBD and colon cancer remain an open question.
TL;DR: The possibility that melatonin might have therapeutic significance via regulation of MMPs may be a novel approach in the treatment of some diseases, and the emerging molecular mechanisms relevant to regulatory actions of melatonin are discussed.
Abstract: Matrix metalloproteinases (MMPs) are part of a superfamily of metal-requiring proteases that play important roles in tissue remodeling by breaking down proteins in the extracellular matrix that provides structural support for cells. The intricate balance in protease/anti-protease stoichiometry is a contributing factor in a number of diseases. Melatonin possesses multifunctional bioactivities including antioxidative, anti-inflammatory, endocrinologic and behavioral effects. As melatonin affects the redox status of tissues, the association of reactive oxygen species (ROS) with tissue injury under different circumstances may be mitigated by melatonin. Redox signaling is expanding into all areas of basic and clinical sciences, and this timely review focuses on the topic of regulation of MMP activities by melatonin. This is a rapidly growing field. Accumulating evidence indicates that oxidative stress plays an important role in regulating the activities of MMPs that are involved in various cellular processes such as cellular proliferation, angiogenesis, apoptosis, invasion and metastasis. This review offers sections on MMPs, melatonin, major physiological and pathophysiological conditions in the context to MMPs, followed by redox signaling mechanisms that are known to influence the cellular processes. Finally, we discuss the emerging molecular mechanisms relevant to regulatory actions of melatonin on the activities of MMPs. The possibility that melatonin might have therapeutic significance via regulation of MMPs may be a novel approach in the treatment of some diseases.
TL;DR: In this article, the authors showed that RORα is mainly located in human Jurkat T-cell nucleus, and it is co-immunoprecipitated with melatonin.
Abstract: Melatonin modulates a wide array of physiological events with pleiotropic effects on the immune system. While the relevance of specific melatonin membrane receptors has been well established for several biological functions, retinoic acid-related orphan receptor alpha (RORα) has been suggested as a mediator of nuclear melatonin signalling by results obtained from pharmacological approaches. However, a melatonin-mediated downstream effect cannot be ruled out, and further evidence is needed to support a direct interaction between melatonin and RORα. Here, we show that RORα is mainly located in human Jurkat T-cell nucleus, and it is co-immunoprecipitated with melatonin. Moreover, immunocytochemistry studies confirmed the co-localization of melatonin and RORα. Melatonin promoted a time-dependent decrease in nuclear RORα levels, suggesting a role in the RORα transcriptional activity. Interestingly, RORα acts as a molecular switch implicated in the mutually exclusive generation of Th17 and Treg cells, both involved in the harm/protection balance of immune conditions such as autoimmunity or acute transplant rejection. Therefore, the identification of melatonin as a natural modulator of RORα gives it a tremendous therapeutic potential for a variety of clinical disorders.
TL;DR: Whether miRNAs play a role in regulation of various gene expression responses to melatonin in MCF‐7 human breast cancer cells is determined and suggested that melatonin may modulate miRNA and gene expression as an anticancer mechanism in human breast cancers cells.
Abstract: MicroRNAs (miRNAs) are small, noncoding RNAs that play a crucial role in regulation of gene expression. Recent studies have shown that miRNAs implicated in initiation and progression of various human cancers, including breast cancer and also analysis of miRNA expression profiles in cancer provide new insights into potential mechanisms of carcinogenesis. Melatonin, N-acetyl-5-methoxytryptamine, is synthesized by the pineal gland in response to the dark/light cycle and has been known to act as a synchronizer of the biological clock. Melatonin has a variety of therapeutic effects, such as immunomodulatory actions, anti-inflammatory effects, and antioxidant actions. Furthermore, melatonin is reported to have an anticancer function including suppression of the metabolism of tumor cells and induction of tumor suppressor genes in cancer cells, including breast cancer cells. In this study, we determined whether miRNAs play a role in regulation of various gene expression responses to melatonin in MCF-7 human breast cancer cells. We examined whole-genome miRNA and mRNA expression and found that 22 miRNAs were differentially expressed in melatonin-treated MCF-7 cells. We further identified a number of mRNAs whose expression level shows a high inverse correlation with miRNA expression. The Gene Ontology (GO) enrichment analysis and pathways analysis were performed for identification of the signaling pathways and biological processes affected by differential expression of miRNA and miRNA-related genes. Our findings suggested that melatonin may modulate miRNA and gene expression as an anticancer mechanism in human breast cancer cells.
TL;DR: Melatonin treatment substantially prevented intracellular ROS production, reversed caspase activation, and forestalled DNA fragmentation induced by TG and FMLP, helping to understand how melatonin controls apoptosis in cells of immune/inflammatory relevance.
Abstract: Apoptosis or programmed cell death plays a critical role in both inflammatory and immune responses. Recent evidence demonstrates that control of leukocyte apoptosis is one of the most striking immune system-related roles of melatonin. For this reason, this study evaluated the protective effects of melatonin on human leukocyte apoptosis induced by sustained cytosolic calcium increases. Such protective effects are likely mediated by melatonin’s free-radical scavenging actions. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin (TG), and/or the calcium-mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (FMLP), induced intracellular reactive oxygen species (ROS) production, caspase activation as well as DNA fragmentation in human leukocytes. Also, TG- and/or FMLP-induced apoptosis was dependent on both cytosolic calcium increases and calcium uptake into mitochondria, because when cells were preincubated with the cytosolic calcium chelator, dimethyl BAPTA, and the inhibitor of mitochondrial calcium uptake, Ru360, TG- and FMLP-induced apoptosis was largely inhibited. Importantly, melatonin treatment substantially prevented intracellular ROS production, reversed caspase activation, and forestalled DNA fragmentation induced by TG and FMLP. Similar results were obtained by preincubating the cells with another well-known antioxidant, i.e., N-acetyl-l-cysteine. To sum up, depletion of intracellular calcium stores induced by TG and/or FMLP triggers different apoptotic events in human leukocytes that are dependent on calcium signaling. The protective effects resulting from melatonin administration on leukocyte apoptosis likely depend on melatonin’s antioxidant action because we proved that this protection is melatonin receptor independent. These findings help to understand how melatonin controls apoptosis in cells of immune/inflammatory relevance.
TL;DR: It is suggested that melatonin may be beneficial as a supplement for treatment of neonatal hypoxic–ischemic brain injury for promoting the proliferation and differentiation of NSCs.
Abstract: Melatonin, an endogenously produced neurohormone secreted by the pineal gland, has a variety of physiological functions and neuroprotective effects. It can modulate the functions of neural stem cells (NSCs) including proliferation and differentiation in embryonic brain tissue but its effect and mechanism on the stem cells in hypoxia remains to be explored. Here, we show that melatonin stimulates proliferation of NSCs during hypoxia. Additionally, it also promoted the differentiation of NSCs into neurons. However, it did not appear to exert an obvious effect on the differentiation of astrocytes. The present results have further shown that the promotional effect of NSCs proliferation by melatonin involved the MT1 receptor and increased phosphorylation of ERK1/2. The effect of melatonin on differentiation of NSCs is linked to altered expression of differentiation-related genes. In the light of these findings, it is suggested that melatonin may be beneficial as a supplement for treatment of neonatal hypoxic-ischemic brain injury for promoting the proliferation and differentiation of NSCs.
TL;DR: In this paper, the authors investigated whether over-expression of inflammatory mediators, oxidative stress, and alterations in biochemical parameters induced by acute exercise could be prevented by melatonin during high-intensity exercise.
Abstract: Strenuous exercise induces inflammatory reactions together with high production of free radicals and subsequent muscle damage. This study was designed to investigate for the first time and simultaneously whether over-expression of inflammatory mediators, oxidative stress, and alterations in biochemical parameters induced by acute exercise could be prevented by melatonin. This indoleamine is a potent, endogenously produced free radical scavenger and a broad-spectrum antioxidant; consequently, it might have positive effects on the recovery following an exercise session. The participants were classified into two groups: melatonin-treated men (MG) and placebo-treated individuals (controls group, CG). The physical test consisted in a constant run that combined several degrees of high effort (mountain run and ultra-endurance). The total distance of the run was 50 km with almost 2800 m of ramp in permanent climbing and very changeable climatic conditions. Exercise was associated with a significant increase in TNF-α, IL-6, IL-1ra (in blood), and also an increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) and isoprostane levels (in urine), and indicated the degree of oxidative stress and inflammation induced. Oral supplementation of melatonin during high-intensity exercise proved efficient in reducing the degree of oxidative stress (lower levels of lipid peroxidation, with a significant increase in antioxidative enzyme activities); this would lead to the maintenance of the cellular integrity and reduce secondary tissue damage. Data obtained also indicate that melatonin has potent protective effects, by preventing over-expression of pro-inflammatory mediators and inhibiting the effects of several pro-inflammatory cytokines. In summary, melatonin supplementation before strenuous exercise reduced muscle damage through modulation of oxidative stress and inflammation signaling associated with this physical challenge.
TL;DR: Antiradical power of wines derived from plant activator‐treated grapes, measured by both DPPH and ABTS, was higher than in their counterparts and this is the first report on the effects of agrochemicals on the melatonin content of red wine.
Abstract: Resistance inducers are a class of agrochemicals, including benzothiadiazole and chitosan, which activate the plant own defence mechanisms. In this work, open-field treatments with plant activators were performed on two red grape (Vitis vinifera L.) varieties cultivated in different localities, Groppello (Brescia, Lombardia, Italy) and Merlot (Treviso, Veneto, Italy). Treatments were carried out every 10 days until the veraison and, after harvesting, experimental wines (microvinificates) were prepared. In general, both melatonin and total polyphenol content, determined by mass spectrometry and Folin-Ciocalteu assay, respectively, were higher in wines produced from grapes treated with resistance inducers than in those obtained from untreated control and conventional fungicide-treated grapes. Accordingly, antiradical power of wines derived from plant activator-treated grapes, measured by both DPPH (2,2-diphenyl-1-picrylhydrazyl) and the ABTS [(2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] radical–scavenging assay, was higher than in their counterparts. To the best of our knowledge, this is the first report on the effects of agrochemicals on the melatonin content of red wine.
TL;DR: The authors reported, for the first time, the occurrence of melatonin in grape seeds, and detected the highest melatonin content in skin, at pre‐véraison, whereas, at véraisons, the highest levels were reported in the seed.
Abstract: Melatonin has been reported in a variety of food plants and, consequently, in a number of plant-derived foodstuffs. In grapevine (Vitis vinifera L.) products, it was found in berry exocarp (skin) of different cultivars and monovarietal wines. Herein, we assessed, by means of mass spectrometry, the occurrence of melatonin in all berry tissues (skin, flesh, and seed) at two different phenological stages, pre-veraison and veraison. We detected the highest melatonin content in skin, at pre-veraison, whereas, at veraison, the highest levels were reported in the seed. Furthermore, during ripening, melatonin decreased in skin, while increasing in both seed and flesh. The relative concentrations of melatonin in diverse berry tissues were somewhat different from those of total polyphenols (TP), the latter measured by the Folin-Ciocalteau assay, and more abundant in seed at pre-veraison and in exocarp at veraison. The highest antiradical activity, determined by both DPPH (2,2-diphenyl-1-pycryl hydrazyl) and ABTS [(2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] radical-scavenging assay, was reported at pre-veraison in seed. To the best of our knowledge, we reported, for the first time, the occurrence of melatonin in grape seeds.
TL;DR: In this article, the authors used the receptor antagonist luzindole to assess the contribution of MT1 melatonin membrane receptor to melatonin effects on cell viability, mitogen-activated protein kinase (MAPKs) activation, and cAMP levels.
Abstract: Melatonin reduces proliferation in many different cancer cell lines. However, studies on the oncostatic effects of melatonin in hepatocarcinoma are limited. We have previously demonstrated that melatonin administration induces cycle arrest, apoptosis, and changes in the expression of its specific receptors in HepG2 human hepatocarcinoma cells. In this study, we used the receptor antagonist luzindole to assess the contribution of MT1 melatonin membrane receptor to melatonin effects on cell viability, mitogen-activated protein kinase (MAPKs) activation, and cAMP levels. Additionally, effects of MT1 inhibition on mRNA levels of cytosolic quinone reductase type-2 (NQO2) receptor and nuclear retinoic acid-related orphan receptor alpha (RORα) were tested. Melatonin, at 1000 and 2500 μm, significantly reduced cell viability. Pre-incubation with luzindole partially inhibited the effects of melatonin on cell viability. Melatonin at 2500 μm significantly reduced cAMP levels, and this effect was partially blocked by luzindole. Both melatonin concentrations increased the expression of phosphorylated p38, ERK, and JNK. ERK activation was completely abolished in the presence of luzindole. NQO2 but not RORα mRNA level significantly increased in luzindole-treated cells. Results obtained provide evidence that the melatonin effects on cell viability and proliferation in HepG2 cells are partially mediated through the MT1 membrane receptor, which seems to be related also with melatonin modulation of cAMP and ERK activation. This study also highlights a possible interplay between MT1 and NQO2 melatonin receptors in liver cancer cells.
TL;DR: Investigation of the antiapoptotic effect of melatonin in an animal model of FHF of viral origin induced by the rabbit hemorrhagic disease virus shows that inhibition of apoptotic mechanisms contributes to the beneficial effects ofmelatonin in rabbits with experimental infection by RHDV and supports a potential hepatoprotective role of mel testosterone in FHF.
Abstract: Hepatocyte apoptosis plays an important role in the development of fulminant hepatic failure (FHF). The objective of this study was to investigate the antiapoptotic effect of melatonin in an animal model of FHF of viral origin induced by the rabbit hemorrhagic disease virus (RHDV). Rabbits were experimentally infected with 2 × 104 hemagglutination units of a RHDV isolate and received melatonin at two concentrations of 10 and 20 mg/kg at 0, 12, and 24 hr postinfection. RHDV infection induced liver apoptosis, with increased caspase-3 immunoexpression and activity and poly(ADP-ribose)polymerase-1 (PARP-1) proteolysis. These effects were attenuated by melatonin in a concentration-dependent manner. Antia-poptotic effects of melatonin were related to a reduced expression of Bax and cytosolic cytochrome c release, increased expression of Bcl-2 and Bcl-xL, and inhibition of caspase-9 activity. Increased thiobarbituric reactive acid substances concentration and oxidized-to-reduced glutathione ratio were significantly prevented by melatonin administration. Melatonin treatment also resulted in a reduction in caspase-8 activity, tumor necrosis factor receptor-1 (TNF-R1) expression, and phosphorylated Janus kinase (JNK) expression, and increased expression of cellular FLICE-inhibitory protein (c-FLIP). Our findings show that inhibition of apoptotic mechanisms contributes to the beneficial effects of melatonin in rabbits with experimental infection by RHDV and supports a potential hepatoprotective role of melatonin in FHF.
TL;DR: In this paper, the authors investigated whether melatonin protects luteinized granulosa cells from reactive oxygen species (ROS) as an antioxidant to enhance progesterone production in the follicle during ovulation.
Abstract: This study investigated whether melatonin protects luteinized granulosa cells from reactive oxygen species (ROS) as an antioxidant to enhance progesterone production in the follicle during ovulation Follicular fluid was sampled at the time of oocyte retrieval in women undergoing in vitro fertilization and embryo transfer (IVF-ET) Melatonin concentrations in the follicular fluid were positively correlated with progesterone concentrations (r = 0342, P 10 ng/mL during the mid-luteal phase) in nine of 14 women (643%), whereas only two of 11 women (181%) showed normal serum progesterone levels in the control group In conclusion, melatonin protects granulosa cells undergoing luteinization from ROS in the follicle and contributes to luteinization for progesterone production during ovulation