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Melatonin protects mast cells against cytotoxicity mediated by chemical stimuli PMACI: Possible clinical use
Abstract
Melatonin has documented cytoprotective effects on a wide variety of immune cells. The mechanism of action on mast cells (RBL-2H3) still remains in the dark. We found that melatonin significantly attenuated phorbol 12-myristate 13-acetate plus calcium ionophore A23187 (PMACI)-induced cytotoxicity in a concentration and time-dependent manner. It appears that the effect of melatonin on mast cells is two-fold: dependent (MT1 and MT2) and independent membrane receptors. In conclusion, melatonin treatment reduced the cytotoxicity, mediated by PMACI, and could provide a useful therapeutic option in processes where an excessive activation of mast cells occurs.
... [10][11][12] In mammals, melatonin is produced by the pineal gland and by a variety of extrapineal tissues; pineal melatonin is secreted into the blood in a circadian manner and with systemic effects, 13 whereas in extrapineal tissues it is produced continuously, with local effects such as those that occur in bone, fatty tissue, brain, and the immune system, among others. 14,15 Extrapineal melatonin plays a pivotal role as an intra, auto and paracrine signal molecule in those tissues where it is synthesized and released. 16 Melatonin is a molecule that is soluble in alcohol and water, with amphiphilicity properties that allow it to cross the plasma membrane freely, and so it can rapidly accumulate within cells and react with the cytosolic target. ...
... 17 An adequate diet to cover the body's energy demands includes the consumption of proteins preferably from fish, fibers of fruit and vegetables, natural largely unrefined sugars, and low fat foods. 18 Melatonin is a normal food component found in yeast and plant material, including edible plant products and medical herbs, 7,12 which can influence the level of melatonin in the circulation and promote healthy benefits by virtue of its cytoprotective, 14 anti-inflammatory, 19 antioxidant 9,20 or anti-apoptotic properties. 14 The effects of melatonin are dose dependent and are related to the time and manner of administration. ...
... 18 Melatonin is a normal food component found in yeast and plant material, including edible plant products and medical herbs, 7,12 which can influence the level of melatonin in the circulation and promote healthy benefits by virtue of its cytoprotective, 14 anti-inflammatory, 19 antioxidant 9,20 or anti-apoptotic properties. 14 The effects of melatonin are dose dependent and are related to the time and manner of administration. It can work at physiological and pharmacological doses but pharmacological doses are usually more effective than physiological ones. ...
Beer is a fermented beverage with a low alcohol content originating from cereal fermentation (barley or wheat). It forms part of the diet for many people. It contains melatonin (N‐acetyl‐5‐methoxytryptamine). Melatonin is a molecule with a wide range of antioxidant, oncostatic, immunomodulatory, and cytoprotective properties. The aim of this work was to review the data supporting the idea that a moderate consumption of beer, because of its melatonin content, is particularly useful in healthy diets and in other physiological situations (such as pregnancy, menopause, and old age). Data source: a) The MEDLINE /PubMed search was conducted from 1975 to April 2022, and b) Our own experience and published studies on melatonin, the immune system, and beer. We provide a review of research on the mechanisms of melatonin generation in beer, its concentrations, and its possible effects on health. The melatonin contained in beer, as part of a healthy diet and in some special physiological situations, could act as a protective factor and improve the quality of life of those who drink it in moderation. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... PMACI is formed by the union of PMA (phorbol-12-myristate 13-acetate) used at doses of 50 Â 10 À8 M and CI (calcium ionophore A23187) used at doses of 5 Â 10 À7 M, for 2 and 12 h. Previous pilot experiments of this study helped towards the selection of the times and concentrations of the combined PMA and CI for optimal cell stimulation in subsequent experiments [Maldonado et al., 2013]. Cell viability was determined by using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT assay; Sigma-Aldrich). ...
... PMACI chemical stimulation triggered a state of hyper-stimulation in the mast cells that led to cellular apoptosis [Maldonado et al., 2013]. Cell viability was determined by using the MTT assay. ...
... Supporting this idea, the luzindole, a non-selective melatonin receptor antagonist, blocked their protection by 1 mM melatonin, but not completely. This may well be due to the lingering presence of MELx in mast cells, which renders any cytoprotection, via melatonin receptor independent [Reiter et al., 2007;Maldonado et al., 2013]. ...
Melatonin is a molecule endogenously produced in a wide variety of immune cells, including mast cells (RBL-2H3). It exhibits immunomodulatory, anti-inflammatory and anti-apoptotic properties. The physiologic mechanisms underlying these activities of melatonin have not been clarified in mast cells. This work is designed to determine the anti-inflammatory effect and mechanism of action of melatonin on activated mast cells. RBL-2H3 were pre-treated with exogenous melatonin (MELx) at physiological (100nM) and pharmacological (1mM) doses for 30 min, washed and activated with PMACI (phorbol 12-myristate 13-acetate plus calcium ionophore A23187) for 2h and 12h. The data shows that pre-treatment of MELx in stimulated mast cells, significantly reduced the levels of endogenous melatonin production (MELn), TNF-alpha and IL-6. These effects are directly related with the MELx concentration used. MELx also inhibited IKK/NF-kB signal transduction pathway in stimulated mast cells. These results indicate a molecular basis for the ability of melatonin to prevent inflammation and for the treatment of allergic inflammatory diseases through the down-regulation of mast cell activation. This article is protected by copyright. All rights reserved.
... Moreover, melatonin shows great functional versatility exhibiting antioxidant [13][14][15][16], oncostatic [17,18], antiaging [19,20], and immunomodulatory [10,11,21] effects. The biochemical mechanisms involved in all of these actions of melatonin involves both receptor-dependents [22,23] and receptor-independents mechanisms [24][25][26]. ...
... Thus, it has been shown that the anti-inflammatory actions of melatonin would be carried out through the NF-κB factor inhibition [126]. Finally, it is interesting to note that melatonin shows a protective role both concentration and time-dependent against mast cells cytotoxicity mediated by phorbo12-myristate 13-acetate plus calcium ionophore A23187 [26]. ...
Melatonin is the major product both synthesized and secreted by the pineal gland during the night period and it is the principal chronobiotic hormone that regulates the circadian rhythms and seasonal changes in vertebrate biology. Moreover, melatonin shows both a broad distribution along the phylogenetically distant organisms and a high functional versatility. At the present time, a significant amount of experimental evidence has been reported in scientific literature and has clearly shown a functional relationship between the endocrine, nervous, and immune systems. The biochemistry basis of the functional communication between these systems is the utilization of a common chemicals signals. In this framework, at present melatonin is considered to be a relevant member of the so-called neuro-endocrine-immunological network. Thus, both in vivo and in vitro investigations conducted in both experimental animals and humans, have clearly documented that melatonin has an important immunomodulatory role. However, most of the published results refer to information on T lymphocytes, i.e., cell-mediated immunity. On the contrary, fewer studies have been carried out on B lymphocytes, the cells responsible for the so-called humoral immunity. In this review, we have focused on the biological role of melatonin in the humoral immunity. More precisely, we report the actions of melatonin on B lymphocytes biology and on the production of different types of antibodies. melatonin in the humoral of melatonin on B lymphocytes melatonin in the humoral called humoral immunity fewer studies have been carried out on called humoral immunity fewer studies have been carried out on information on T lymphocytes, i.e., cell information on T lymphocytes, i.e., cell documented that melatonin owever, most of the published documented that melatonin conducted documented that melatonin conducted immunological network. in both immunological network. is considered to be a relevant tilization of s considered to be a relevant of a common chemical 4
... Moreover, melatonin shows great functional versatility exhibiting antioxidant [13][14][15][16], oncostatic [17,18], antiaging [19,20], and immunomodulatory [10,11,21] effects. The biochemical mechanisms involved in all of these actions of melatonin involves both receptor-dependents [22,23] and receptor-independents mechanisms [24][25][26]. ...
... Thus, it has been shown that the anti-inflammatory actions of melatonin would be carried out through the NF-κB factor inhibition [126]. Finally, it is interesting to note that melatonin shows a protective role both concentration and time-dependent against mast cells cytotoxicity mediated by phorbo12-myristate 13-acetate plus calcium ionophore A23187 [26]. ...
... In mammals, melatonin is synthesized in many tissues and organs, such as gastrointestinal, respiratory, genitourinary, immune systems, and skin [7][8][9][10][11][12][13]. Additionally, melatonin shows a remarkable functional versatility exhibiting antioxidant [14][15][16][17][18], oncostatic [19,20], antiaging [21,22], and immunomodulatory [11,12,23] effects. The molecular mechanisms responsible for the pleiotropic effects of melatonin involve mechanisms of action receptor-dependents [24,25] as well as receptor-independents [25][26][27][28]. ...
... In mammals, melatonin is synthesized in many tissues and organs, such as gastrointestinal, respiratory, genitourinary, immune systems, and skin [7][8][9][10][11][12][13]. Additionally, melatonin shows a remarkable functional versatility exhibiting antioxidant [14][15][16][17][18], oncostatic [19,20], antiaging [21,22], and immunomodulatory [11,12,23] effects. The molecular mechanisms responsible for the pleiotropic effects of melatonin involve mechanisms of action receptor-dependents [24,25] as well as receptor-independents [25][26][27][28]. ...
Melatonin is the main secretory product synthesized and secreted by the pineal gland during the night. Melatonin is a pleitropic molecule with a wide distribution within phylogenetically distant organisms and has a great functional versatility, including the regulation of circadian and seasonal rhythms and antioxidant and anti-inflammatory properties. It also possesses the capacity to modulate immune responses by regulation of the TH1/TH2 balance and cytokine production. Immune system eradicates infecting organisms without serious injury to host tissues, but sometimes these responses are inadequately controlled, giving rise to called hypersensitivity diseases, or inappropriately targeted to host tissues, causing the autoimmune diseases. In clinical medicine, the hypersensitivity diseases include the allergic or atopic diseases and the hallmarks of these diseases are the activation of TH2 cells and the production of IgE antibody. Regarding autoimmunity, at the present time we know that the key events in the development of autoimmunity are a failure or breakdown of the mechanisms normally responsible for maintaining self-tolerance in B lymphocytes, T lymphocytes, or both, the recognition of self-antigens by autoreactive lymphocytes, the activation of these cells to proliferate and differentiate into effector cells, and the tissue injury caused by the effector cells and their products. Melatonin treatment has been investigated in atopic diseases, in several animal models of autoimmune diseases, and has been also evaluated in clinical autoimmune diseases. This review summarizes the role of melatonin in atopic diseases (atopic dermatitis and asthma) and in several autoimmune diseases, such as arthritis rheumatoid, multiple sclerosis, systemic lupus erythematosus, type 1 diabetes mellitus, and inflammatory bowel diseases.
... 7 Melatonin, owing to its antioxidant action, could act by reducing oxidative stress or blocking some of the mast cell activation pathways, such as the nuclear factor NF-KB, thus reducing the synthesis and release of proinflammatory cytokines such as IL-6 or TNF-alpha, which are components of the content of mast cell granules, and exerting a cytoprotective role. 8,9 Therefore, blocking the NF-KB factor in mast cells may be one of the mechanisms of action of melatonin, although it is not the only one. Based on how melatonin acts on other cells containing granules that undergo exo-endocytosis, such as neurons or epithelial cells, its intervention was at the cytoskeleton level by modulating it, 10 preventing its assembly and reducing their exoendocytosis, and even acting on adhesion molecules. ...
... Increases the secretory activity through raised endosomal compartments [59] Increases in the number of cells and diameter [59,60] Could synthesize melatonin [58,61] Neutrophil Protects neutrophils from oxidative stress-induced apoptosis [62] Reduces ROS generation [62,63] Restores their functions: phagocytosis, degranulation, NETosis [62,64] Suppresses the release of CXCL8, CCL2, CCL4, and MMP9 by blockage of p38 MAPK and Akt signaling [65] Suppresses the release of cytokines: TNF-a, IL-8 [66] Modulates the migration through the endothelial layer by blocking the ERK phosphorylation signal [67,68] Reduces the microbicidal activity [69] Eosinophil Suppresses eosinophils activity [70] Decreases eosinophil number [71,72] Mast cell Avoid degranulation [73] Regulates differentiation and cellular proliferation [74][75][76][77] Restores circadian rhythms [78] Reduces the cytotoxicity [79] Inhibits the expression of proinflammatory cytokines and COX2 [75,80] Could synthesize melatonin [81] The pineal gland is directly involved in innate and adaptive immune responses, the expression of MHC-II in antigen-presenting cells or APCs (macrophages and dendritic cells), as well as in peritoneal macrophages is increased after MLT supplementation; it has been suggested that this neurohormone can prevent age-related changes in the immune system [38,39]. MLT has been reported to play an anti-inflammatory role in innate immune activation, inhibit the de-acetylation of NF-k B by sirtuin1, inhibit NF-k B activity in the septic mouse, reduce the proinflammatory response mediated by this same transcription factor, and restore mitochondrial homeostasis [38]. ...
Psychoneuroendocrinoimmunology is the area of study of the intimate relationship between immune, physical, emotional, and psychological aspects. This new way of studying the human body and its diseases was initiated in the last century’s first decades. However, the molecules that participate in the communication between the immune, endocrine, and neurological systems are still being discovered. This paper aims to describe the development of psychoneuroendocrinoimmunology, its scopes, limitations in actual medicine, and the extent of melatonin within it.
... This article is protected by copyright. All rights reserved was confirmed as a cytoprotectant modulated by phorbol 12-myristate 13-acetate plus calcium ionophore A23187 (PMACI) through the NF-κB pathway 94 . However, the mechanism of melatonin activation in reducing inflammatory toxicity remains unclear. ...
Our daily rhythmicity is controlled by a circadian clock with a specific set of genes located in the suprachiasmatic nucleus in the hypothalamus. Mast cells (MCs) are major effector cells that play a protective role against pathogens and inflammation. MC distribution and activation are associated with the circadian rhythm via two major pathways, IgE/FcεRI‐ and IL‐33/ST2‐mediated signaling. Furthermore, there is a robust oscillation between clock genes and MC‐specific genes. Melatonin is a hormone derived from the amino acid tryptophan and is produced primarily in the pineal gland near the center of the brain, and histamine is a biologically active amine synthesized from the decarboxylation of the amino acid histidine by the 1‐histidine decarboxylase enzyme. Melatonin and histamine are previously reported to modulate circadian rhythms by pathways incorporating various modulators in which the nuclear factor binding near the κ light chain gene in B cells, NF‐κB, is the common key factor. NF‐κB interacts with the core Clock genes and disrupts the production of proinflammatory cytokine mediators such as IL‐6, IL‐13, and TNF‐α. Currently there has been no study evaluating the interdependence between melatonin and histamine with respect to circadian oscillations in MCs. Accumulating evidence suggests that restoring circadian rhythms in MCs by targeting melatonin and histamine via NF‐κB may be promising therapeutic strategy for MC‐mediated inflammatory diseases. This review summarizes recent findings for circadian‐mediated MC functional roles and activation paradigms, as well as the therapeutic potentials of targeting circadian‐mediated melatonin and histamine signaling in MC‐dependent inflammatory diseases.
... The cell membrane is an important site for exchange of information, substances and energy between cells and the external environment, and the cell membrane plays an important role in resisting external stimuli and preventing cell damage [11,12]. The integrity of the cell membrane is the basis for the normal function of cells, and the toxic effect of drugs on cells is closely related to changes in membrane structure [13]. ...
Pomacea canaliculata hemocytes are the main functional cells in the immune defense system, and hemocyte destruction disrupts the immune response mechanism of P. canaliculata, resulting in abnormal growth, development, reproduction, and even death. Our previous study found that Pedunsaponin A significantly affects P. canaliculata hemocyte structure. This study further investigated the damaging effects of Pedunsaponin A on P. canaliculata hemocytes. The cell mortality rate results showed that the hemocyte mortality was significantly increased after treatment with Pedunsaponin A, and the mortality rate exhibited a significant positive correlation with treatment time and dose. The membrane potential results showed that the cell membranes of P. canaliculata hemocytes exhibited time-dependent membrane depolarization after 40 mg/L Pedunsaponin A treatment. At 36 h, the cell depolarization rate in the Pedunsaponin A treatment group was 41.43%, which was significantly greater than the control group (6.24%). The cytoskeleton results showed that Pedunsaponin A led to disordered and dispersed arrangement of microfilaments and changes in the cytoskeletal structure. The apoptosis and cell cycle results showed that Pedunsaponin A induced apoptosis and influenced the cell cycle to some extent. These results showed that the cell membrane and cytoskeleton of P. canaliculata hemocytes were damaged after treatment with Pedunsaponin A, which led to an increase in cell mortality, dysfunction, cell cycle abnormalities and apoptosis. This study provides a foundation for further identification of the site of Pedunsaponin A activity on hemocytes.
... www.drugdiscoverytoday.com 1415 and might enhance cancer stimulatory cytokines. A higher risk of breast cancer development has been linked to insufficient sleep, which also indicates role for melatonin in the development of this disease [92]. In breast cancer, the oncostatic activities of melatonin have been reported in vitro and in vivo. ...
The development of novel local therapies for thermal burns (TB) and their pathogenetic rationale are a pressing challenge. Melatonin (MT) is an endogenous factor of hemostasis regulation with pleiotropic potential. The aim of this study was to assess some parameters of tissue regeneration, the functional state of mast cells and the levels of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) in the experimentally induced TB treated with the original MT-enriched dermal film (DF). A second-degree burn (3.5% of the total body surface area) was modelled by exposing a patch of skin to hot water. Applications of 12 cm2 DF enriched with 5 mg/g MT were performed every day for 5 days. The following parameters were calculated: the wound area, the rate of wound epithelization, the number of MC in the wound, the intensity of degranulation, and the levels of MMP-9 and VEGF expression. Over the course of treatment, the absolute wound area shrank by 35%, its epithelization rate increased, the number of MC rose, their functional state changed, and the expression of ММР-9 and VEGF increased. A negative correlation was established between the wound area and the expression of ММР-9 and VEGF, as well as between the wound area and the degranulation coefficient. Applications of MT-enriched DF resulted in the reduction of the wound area, higher epithelization rate, an increase in the total MC count and degranulation intensity on days 5 and 10; it also led to a reduction in the total MC count and a loss in degranulation intensity on day 20 (166.87 (154.95; 178.78) un/mm2 vs. 464.84 (452.92; 476.76) un/mm2) in the group of intact animals), an increase in MMP-9 expression on day 5 (14.20 (11.30; 18.10) vs. 3.30 (2.20; 4.40) in the intact group), an increase in VEGF expression on days 5 and 10 (33.00 (30.20; 34.90) vs 25.40 (22.20; 29.30) in the intact group), and a reduction in MMP-9 expression on days 10 and 20 after thermal injury.
Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.
In addition to the well known role of mast cells in immunity to multi-cellular parasites and in the pathogenesis of allergy and asthma, the importance of mast cells in the immune defense against bacteria and viruses is increasingly being recognized. Their location in the skin, gut, and airways puts mast cells in an ideal location to encounter and respond to pathogens, and in order to perform this function, these cells express a variety of pattern recognition receptors, including Toll-like receptors (TLRs). Mast cells respond to TLR ligands by secreting cytokines, chemokines, and lipid mediators, and some studies have found that TLR ligands can also cause degranulation, although this finding is contentious. In addition, stimulation via TLR ligands can synergize with signaling via the FcεRI, potentially enhancing the response of the cells to antigen in vivo. A great deal is now known about TLR signaling pathways. Some features of these pathways are cell type-specific, however, and work is under way to fully elucidate the TLR signaling cascades in the mast cell. Already, some interesting differences have been identified. This review aims to address what is known about the responses of mast cells to TLR ligands and the signaling pathways involved. Given the location of mast cells at sites exposed to the environment, the response of these cells to TLR ligands must be carefully regulated. The known mechanisms behind this regulation are also reviewed here.
Melatonin is a highly evolutionary conserved endogenous molecule that is mainly produced by the pineal gland, but also by other nonendocrine organs, of most mammals including man. In the recent years, a variety of anti-inflammatory and antioxidant effects have been observed when melatonin is applied exogenously under both in vivo and in vitro conditions. A number of studies suggest that this indole may exert its anti-inflammatory effects through the regulation of different molecular pathways. It has been documented that melatonin inhibits the expression of the isoforms of inducible nitric oxide synthase and cyclooxygenase and limits the production of excessive amounts of nitric oxide, prostanoids, and leukotrienes, as well as other mediators of the inflammatory process such as cytokines, chemokines, and adhesion molecules. Melatonin's anti-inflammatory effects are related to the modulation of a number of transcription factors such as nuclear factor kappa B, hypoxia-inducible factor, nuclear factor erythroid 2-related factor 2, and others. Melatonin's effects on the DNA-binding capacity of transcription factors may be regulated through the inhibition of protein kinases involved in signal transduction, such as mitogen-activated protein kinases. This review summarizes recent research data focusing on the modulation of the expression of different inflammatory mediators by melatonin and the effects on cell signaling pathways responsible for the indole's anti-inflammatory activity. Although there are a numerous published reports that have analyzed melatonin's anti-inflammatory properties, further studies are necessary to elucidate its complex regulatory mechanisms in different cellular types and tissues.
Amyloid-beta (Aβ) pathology is related to mitochondrial dysfunction accompanied by energy reduction and an elevated production of reactive oxygen species (ROS). Monomers and oligomers of Aβ have been found inside mitochondria where they accumulate in a time-dependent manner as demonstrated in transgenic mice and in Alzheimer's disease (AD) brain. We hypothesize that the internalization of extracellular Aβ aggregates is the major cause of mitochondrial damage and here we report that following the injection of fibrillar Aβ into the hippocampus, there is severe axonal damage which is accompanied by the entrance of Aβ into the cell. Thereafter, Aβ appears in mitochondria where it is linked to alterations in the ionic gradient across the inner mitochondrial membrane. This effect is accompanied by disruption of subcellular structure, oxidative stress, and a significant reduction in both the respiratory control ratio and in the hydrolytic activity of ATPase. Orally administrated melatonin reduced oxidative stress, improved the mitochondrial respiratory control ratio, and ameliorated the energy imbalance.
Psoriasis involves skin inflammation that often worsens with stress, but the mechanism of this effect remains obscure. We have shown that corticotropin-releasing hormone (CRH) is increased in the serum of patients with psoriasis. A peptide, neurotensin (NT), can trigger skin histamine release and augment the ability of CRH to increase skin vascular permeability.
To investigate the serum level of NT, and the expression of genes for NT and NT receptor-1 (NTR-1) in lesional and nonlesional skin of patients with psoriasis, compared with normal controls. Also, to study the effect of NT on human mast cell release of vascular endothelial growth factor (VEGF), which is increased in psoriatic skin.
Serum was obtained from patients with psoriasis (n = 56) and controls (n = 33); NT levels were measured with the Milliplex microbead assay. Biopsies were obtained from the lesional and nonlesional skin of patients with chronic plaque psoriasis (n = 40), who had not received any treatment for at least 15 days and were free of any systemic inflammatory diseases. Control skin samples were obtained from healthy subjects (n = 30). Expression of genes for NT and NTR-1 in the skin was evaluated by quantitative reverse transcriptase-polymerase chain reaction. LAD2 human mast cells were stimulated by NT (1 μmol L(-1)) for 24 h and VEGF was measured by enzyme-linked immunosorbent assay.
Serum NT was increased in patients with psoriasis, while expression of genes for NT and NTR-1 in lesional skin was decreased compared with controls. NT induced VEGF release from mast cells and was augmented by interleukin-33.
NT may play a role in psoriasis pathogenesis and its worsening by stress, at least in part through activation of skin mast cells.
Over the past 20 y, the hormone melatonin was found to be produced in extrapineal sites, including cells of the immune system. Despite the increasing data regarding the biological effects of melatonin on the regulation of the immune system, the effect of this molecule on T cell survival remains largely unknown. Activation-induced cell death plays a critical role in the maintenance of the homeostasis of the immune system by eliminating self-reactive or chronically stimulated T cells. Because activated T cells not only synthesize melatonin but also respond to it, we investigated whether melatonin could modulate activation-induced cell death. We found that melatonin protects human and murine CD4(+) T cells from apoptosis by inhibiting CD95 ligand mRNA and protein upregulation in response to TCR/CD3 stimulation. This inhibition is a result of the interference with calmodulin/calcineurin activation of NFAT that prevents the translocation of NFAT to the nucleus. Accordingly, melatonin has no effect on T cells transfected with a constitutively active form of NFAT capable of migrating to the nucleus and transactivating target genes in the absence of calcineurin activity. Our results revealed a novel biochemical pathway that regulates the expression of CD95 ligand and potentially other downstream targets of NFAT activation.
Mast cells take part of armamentarium immunologic for host defense against parasitic and bacterial infections. They are derived from bone marrow progenitors and can be activated by immunological and chemical stimuli in order to get its degranulation. The activation of mast cells generates a signalling cascade leaded to the rapid release of vasoactives and pro-inflammatory mediators. Melatonin (N-acetyl-5-methoxytryptamine) is a molecule with antioxidant, cytoprotective and immunomodulatory actions. It was initially known to be produced exclusively in the pineal gland but melatonin synthesis has been found in different sites of the organism, and a major source of extrapineal melatonin is the immune system. The aim of the present study was to prove if the rat mast cell line (RBL-2H3) synthesizes and releases melatonin, also to explain its possible mechanism of action. We report that both resting and stimulated mast cells synthesize and release melatonin. We also report that the necessary machinery to synthesize melatonin is present in mast cells and that these cells showed the presence of MT1 and MT2 melatonin membrane receptors. Those results indicated that the melatonin would be able to exert a regulatory effect on inflammatory reactions mediated by mast cells.
To characterize gene expression in activated mast cells more comprehensively than heretofore, we surveyed the changes in genetic transcripts by the method of serial analysis of gene expression in the RBL-2H3 line of rat mast cells before and after they were stimulated through their receptors with high affinity for immunoglobulin E (FcepsilonRI). A total of 40,759 transcripts derived from 11,300 genes were analyzed. Among the diverse genes that had not been previously associated with mast cells and that were constitutively expressed were those for the cytokine macrophage migration inhibitory factor neurohormone receptors such as growth hormone- releasing factor and melatonin and components of the exocytotic machinery. In addition, several dozen transcripts were differentially expressed in response to antigen-induced clustering of the FcepsilonRI. Included among these were the genes for preprorelaxin, mitogen-activated protein kinase kinase 3, and the dual specificity protein phosphatase, rVH6. Significantly, the majority of genes differentially expressed in this well-studied model of mast cell activation have not been identified before this analysis.
Aerobic cells use oxygen for the production of 90-95% of the total amount of ATP that they use. This amounts to about 40 kg ATP/day in an adult human. The synthesis of ATP via the mitochondrial respiratory chain is the result of electron transport across the electron transport chain coupled to oxidative phosphorylation. Although ideally all the oxygen should be reduced to water by a four-electron reduction reaction driven by the cytochrome oxidase, under normal conditions a small percentage of oxygen may be reduced by one, two, or three electrons only, yielding superoxide anion, hydrogen peroxide, and the hydroxyl radical, respectively. The main radical produced by mitochondria is superoxide anion and the intramitochondrial antioxidant systems should scavenge this radical to avoid oxidative damage, which leads to impaired ATP production. During aging and some neurodegenerative diseases, oxidatively damaged mitochondria are unable to maintain the energy demands of the cell leading to an increased production of free radicals. Both processes, i.e., defective ATP production and increased oxygen radicals, may induce mitochondrial-dependent apoptotic cell death. Melatonin has been reported to exert neuroprotective effects in several experimental and clinical situations involving neurotoxicity and/or excitotoxicity. Additionally, in a series of pathologies in which high production of free radicals is the primary cause of the disease, melatonin is also protective. A common feature in these diseases is the existence of mitochondrial damage due to oxidative stress. The discoveries of new actions of melatonin in mitochondria support a novel mechanism, which explains some of the protective effects of the indoleamine on cell survival.
Melatonin was found to be a potent free radical scavenger in 1993. Since then over 800 publications have directly or indirectly confirmed this observation. Melatonin scavenges a variety of reactive oxygen and nitrogen species including hydroxyl radical, hydrogen peroxide, singlet oxygen, nitric oxide and peroxynitrite anion. Based on the analyses of structure-activity relationships, the indole moiety of the melatonin molecule is the reactive center of interaction with oxidants due to its high resonance stability and very low activation energy barrier towards the free radical reactions. However, the methoxy and amide side chains also contribute significantly to melatonin's antioxidant capacity. The N-C=O structure in the C3 amide side chain is the functional group. The carbonyl group in the structure of N-C=O is key for melatonin to scavenge the second reactive species and the nitrogen in the N-C=O structure is necessary for melatonin to form the new five membered ring after melatonin's interaction with a reactive species. The methoxy group in C5 appears to keep melatonin from exhibiting prooxidative activity. If the methoxy group is replaced by a hydroxyl group, under some in vitro conditions, the antioxidant capacity of this molecule may be enhanced. However, the cost of this change are decreased lipophility and increased prooxidative potential. Therefore, in in vivo studies the antioxidant efficacy of melatonin appears to be superior to its hydroxylated counterpart. The mechanisms of melatonin's interaction with reactive species probably involves donation of an electron to form the melatoninyl cation radical or through an radical addition at the site C3. Other possibilities include hydrogen donation from the nitrogen atom or substitution at position C2, C4 and C7 and nitrosation. Melatonin also has the ability to repair damaged biomolecules as shown by the fact that it converts the guanosine radical to guanosine by electron transfer. Unlike the classical antioxidants, melatonin is devoid of prooxidative activity and all known intermediates generated by the interaction of melatonin with reactive species are also free radical scavengers. This phenomenon is defined as the free radical scavenging cascade reaction of the melatonin family. Due to this cascade, one melatonin molecule has the potential to scavenge up to 4 or more reactive species. This makes melatonin very effective as an antioxidant. Under in vivo conditions, melatonin is often several times more potent than vitamin C and E in protecting tissues from oxidative injury when compared at an equivalent dosage (micromol/kg). Future research in the field of melatonin as a free radical scavenger might be focused on: 1), signal transduction and antioxidant enzyme gene expression induced by melatonin and its metabolites, 2), melatonin levels in tissues and in cells, 3), melatonin structure modifications, 4), melatonin and its metabolites in plants and, 5), clinical trials using melatonin to treat free radical related diseases such as Alzheimer's, Parkinson's, stroke and heart disease.
Our results show that melatonin and N-acetyl-5-methoxykynurenamine (aMK) physiologically regulate both the electron transport chain (ETC) and OXPHOS, increasing the electron transport and ATP synthesis by normal mitochondria. Melatonin also counteracts mitochondrial oxidative damage induced by t-butyl hydroperoxide, recovering glutathione levels and ATP production. However, the effects of melatonin not only depend of its antioxidant properties, since the indoleamine specifically interacts with complex I and IV of the ETC increasing their activity. Experiments in vivo showed that melatonin administration prevents sepsis-induced ETC damage decreasing the activity and expression of INOS and mtNOS, thus reducing intramitochondrial nitric oxide (NO) and peroxynitrite (ONOO-) levels. Consequently, mitochondrial ETC ad ATP production recovered to normal conditions. The presence of specific binding of melatonin in mitochondrial matrix led us to explore the genomic role of the indoleamine in these organelles. In vivo and in vitro experiments showed that administration of melatonin increased mtONA transcriptional activity of the subunits 1-3 of the complex IV. These effects correlated well with the effects of melatonin on complex IV activity. The data suggest a new rate for melatonin to regulate mitochondrial homeostasis. Due to the relationships between mitochondrial damage, aging and neurodegenerative diseases, the effects of melatonin here described further support its antiaging and neuroprotective properties.
To preserve the central nervous system (CNS) function after a traumatic injury, therapeutic agents must be administered to protect neurons as well as glial cells. Cell death in CNS injuries and diseases are attributed to many factors including glutamate toxicity and oxidative stress. We examined whether melatonin, a potent anti-oxidant and free radical scavenger, would attenuate apoptotic death of rat C6 astroglial cells under glutamate excitotoxicity and oxidative stress. Exposure of C6 cells to 500 microM L-glutamic acid (LGA) and 100 microm hydrogen peroxide (H(2)O(2)) for 24 hr caused significant increases in apoptosis. Apoptosis was evaluated by Wright staining and ApopTag assay. Melatonin receptor 1 appeared to be involved in the protection of these cells from excitotoxic and oxidative damage. Cells undergoing excitotoxic and oxidative stress for 15 min were then treated with 150 nM melatonin, which prevented Ca(2+)influx and cell death. Western blot analyses showed alterations in Bax and Bcl-2 expression resulting in increased Bax:Bcl-2 ratio during apoptosis. Western blot analyses also showed increases in calpain and caspase-3 activities, which cleaved 270 kD alpha-spectrin at specific sites to generate 145 kD spectrin breakdown product (SBDP) and 120 kD SBDP, respectively. However, 15-min post-treatment of C6 cells with melatonin dramatically reduced Bax:Bcl-2 ratio and proteolytic activities, decreasing LGA or H(2)O(2)-induced apoptosis. Our data showed that melatonin prevented proteolysis and apoptosis in C6 astroglial cells. The results suggest that melatonin may be an effective cytoprotective agent against glutamate excitotoxicity and oxidative stress in CNS injuries and diseases.
The neurohormone melatonin is involved in the regulation of many physiological functions, in particular those related to circadian and seasonal rhythms. In mammals, melatonin activates two GPCRs, named MT1 and MT2, and ligands of these receptors have been proposed for the treatment of different pathologies. In this article we describe the results of our researches in the field of melatonin receptor ligands, pointing the attention to the investigation of structure-activity relationships and to the development of novel MT2 selective antagonists. Molecular modeling studies led us to formulate a hypothesis about the structural requirements for MT2 selective antagonism. This hypothesis was supported by 3D-QSAR analysis, that allowed the definition of the molecular determinants correlated with binding affinity, receptor subtype selectivity and intrinsic activity. Three-dimensional models of the MT1 and MT2 receptors were built by homology modeling and they provided an explanation, at the receptor level, for the MT2 receptor selectivity evidenced by the antagonists. The information obtained from our ligand-based and structure-based studies was exploited for the design of different series of potent and selective melatonin receptor antagonists with novel structures.
Melatonin is known as an antistress and immunostimulator compound while glucocorticoids have immunosuppressive function. The mechanism of action of both the hormones on immune cells is still a question. We found that melatonin improved the effect of dexamethasone (synthetic glucocorticoid) induced immunosuppression of splenocytes and bone marrow GM-CFU along with increased production of serum IL-2, IgG and the receptor expression for melatonin and glucocorticoid in spleen that might be responsible for the proliferation of immune cells. Thus, seasonal variation in peripheral melatonin might be responsible for the improvement of immune status under different stress conditions experienced by the rodents for better survival.
The T-cell immunoglobulin and mucin domain (Tim) gene family is a relatively newly discovered group of molecules with a conserved structure and important immunologic functions. Tim molecules express on many types of immune cells including T cells, B cells, dendritic cells, macrophages,
and mast cells that have been shown to be involved in asthma, allergic rhinitis, food allergy, and autoimmunity. Tim-1‐Tim-4 interaction promotes Th2 cytokine responses, and blocking this interaction can decrease airway inflammation in asthma and in allergic rhinitis. Tim-3 stimulates
mast cells to produce Th2 cytokines, and anti‐Tim-3 is able to dampen asthmatic inflammation. The Tim-3 ligand was shown to be greatly enhanced on intestinal epithelial cells in patients with food allergy and Tim-4 may play a role in maintaining oral tolerance and prevention of food
allergy. Tim-3 deregulation plays a role in the pathogenesis of multiple sclerosis. Increased Tim-1 expression has been shown in mononuclear cells from systemic lupus erythematosus patients and Tim-3 may be involved in a protective role in rheumatoid arthritis.
The purpose of this study was to determine whether melatonin treatment would mitigate retinal ganglion cell (RGC) death in the developing retina following a hypoxic insult. Lipid peroxidation (LPO), glutathione (GSH), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) concentrations, expression of vascular endothelial growth factor receptors, Flt-1 and Flk-1, release of cytochrome c from mitochondria, and caspase-3 expression were examined in the retinas of 1-day-old rats at 3 hr to 14 days after a hypoxic exposure. The mRNA and protein expression of Flt-1 and Flk-1 and the tissue concentration of LPO, TNF-α, and IL-1β were upregulated significantly after the hypoxic exposure, whereas the content of GSH was decreased significantly. RGC cultures also showed increased LPO and decreased GSH levels after hypoxic exposure but these effects were reversed in cells treated with melatonin. TNF-α and IL-1β expression was specifically located on microglial cells, whereas Flt-1 and Flk-1 was limited to RGCs as confirmed by double immunofluorescence labeling. Cultures of hypoxic microglial cells treated with melatonin showed a significant reduction in the release of these cytokines as compared to untreated hypoxic cells. Hypoxia induced increase in the cytosolic cytochrome c and caspase-3 in RGCs was attenuated with melatonin treatment. The results suggest that, in hypoxic injuries, melatonin is neuroprotective to RGCs in the developing retina through its antioxidative, anti-inflammatory, and anti-apoptotic effects. Melatonin suppressed Flt-1 and Flk-1 expression in retinal blood vessels, which may result in reduced retinal vascular permeability and it also preserved mitochondrial function as shown by a reduction in cytochrome c leakage into the cytosol. The results may have therapeutic implications for the management of retinopathy of prematurity.
Alzheimer’s disease (AD) is a highly complex neurodegenerative disorder of the aged that has multiple factors which contribute to its etiology in terms of initiation and progression. This review summarizes these diverse aspects of this form of dementia. Several hypotheses, often with overlapping features, have been formulated to explain this debilitating condition. Perhaps the best-known hypothesis to explain AD is that which involves the role of the accumulation of amyloid-β peptide in the brain. Other theories that have been invoked to explain AD and summarized in this review include the cholinergic hypothesis, the role of neuroinflammation, the calcium hypothesis, the insulin resistance hypothesis, and the association of AD with peroxidation of brain lipids. In addition to summarizing each of the theories that have been used to explain the structural neural changes and the pathophysiology of AD, the potential role of melatonin in influencing each of the theoretical processes involved is discussed. Melatonin is an endogenously produced and multifunctioning molecule that could theoretically intervene at any of a number of sites to abate the changes associated with the development of AD. Production of this indoleamine diminishes with increasing age, coincident with the onset of AD. In addition to its potent antioxidant and anti-inflammatory activities, melatonin has a multitude of other functions that could assist in explaining each of the hypotheses summarized above. The intent of this review is to stimulate interest in melatonin as a potentially useful agent in attenuating and/or delaying AD.
Melatonin was detected by an improved immunocytochemical technique in the cell nuclei of most tissues studied including several brain areas, pineal gland, Harderian gland, gut, liver, kidney, and spleen from rodents and primates. Cryostat sections from tissues fixed in Bouin's fluid, formalin, or acetone/ethanol were used. The nuclear staining appeared primarily associated with the chromatin. The nucleoli did not exhibit a positive reaction. The melatonin antiserum was used in the range of 1:500 to 1:5,000. Incubation of the antibody with an excess of melatonin resulted in the complete blockade of nuclear staining. Pretreatment of the sections with proteinase K (200–1,000 ng/ml) prevented the positive immunoreaction. In a second aspect of the study, we estimated the concentration of melatonin by means of radioimmunoassay in the nuclear fraction of several tissues including cerebral cortex, liver, and gut. The subcutaneous injection of melatonin (500 μg/kg) to rats resulted, after 30 min, in a rapid increase in the nuclear concentration of immunoreactive melatonin which varied in a tissue-dependent manner. However, samples collected 3 h after the injection showed that melatonin levels had decreased to control values. Pinealectomy in rats resulted in a clear reduction in the nuclear content of melatonin in the cerebral cortex and liver but not in the gut. The results of these studies suggest that melatonin may interact with nuclear proteins and that the indole may have an important function at the nuclear level in a variety of mammalian tissues.
Melatonin (N-acetyl-5-methoxytryptamine) was initially thought to be produced exclusively in the pineal gland. Subsequently its synthesis was demonstrated in other organs, for example, the retinas, and very high concentrations of melatonin are found at other sites, for example, bone marrow cells and bile. The origin of the high level of melatonin in these locations has not been definitively established, but it is likely not exclusively of pineal origin. Melatonin has been shown to possess anti-inflammatory effects, among a number of actions. Melatonin reduces tissue destruction during inflammatory reactions by a number of means. Thus melatonin, by virtue of its ability to directly scavenge toxic free radicals, reduces macromolecular damage in all organs. The free radicals and reactive oxygen and nitrogen species known to be scavenged by melatonin include the highly toxic hydroxyl radical (·OH), peroxynitrite anion (ONOO−), and hypochlorous acid (HOCl), among others. These agents all contribute to the inflammatory response and associated tissue destruction. Additionally, melatonin has other means to lower the damage resulting from inflammation. Thus, it prevents the translocation of nuclear factor-kappa B (NF-κB) to the nucleus and its binding to DNA, thereby reducing the upregulation of a variety of proinflammatory cytokines, for example, interleukins and tumor neurosis factor-alpha. Finally, there is indirect evidence that melatonin inhibits the production of adhesion molecules that promote the sticking of leukocytes to endothelial cells. By this means melatonin attenuates transendothelial cell migration and edema, which contribute to tissue damage.
Endometriosis (EMS) is a chronic, estrogen-dependent inflammatory disease characterized by growth of endometrial tissue outside the uterine cavity. Symptoms in EMS patients include severe pelvic pain, dysmenorrhea, dyspareunia and infertility. To date, medical therapies are mostly based on hormonal suppressive drugs that induce a hypoestrogenic state. Although being effective regarding the reduction of endometriotic tissue masses and pelvic pain, this treatment is accompanied by severe side effects. Since EMS is associated with chronic inflammation, novel therapeutic strategies also focus on immune modulating drugs. However, little is known about how and to what extent immune cell subsets contribute to the network of locally produced cytokines, chemokines and other mitogenic factors that modulate the growth of ectopic endometrial implants and the inflammation associated with them. Mast cells (MCs) are known to be key players of the immune system, especially during allergic reactions. However, in recent years MCs have been identified to exhibit a far broader range of functions and to be involved in host defense and wound healing responses. Here, recent reports that imply an involvement of MCs in EMS has been reviewed, while the value of novel mouse models for clarifying their contribution to the pathology of this condition has been discussed.
Acute sport exercise leads to a strong stimulation of muscle tissue and a change in the organism energy demands. This study was designed to investigate the effect of oral melatonin supplementation on human physiological functions associated with acute exercise. Immune, endocrine and metabolic parameters were measured in 16 young male football players, who were divided into two groups, an experimental group (supplementation with 6 mg of melatonin administered 30 min prior to exercise) and a control group (placebo without melatonin). They performed a continuous exercise of high intensity (135 beats/min). Samples were collected 30 min before the exercise and 3, 15 and 60 min during the exercise. The results indicated that the acute sport training presented: a) increased lipid peroxidation products (MDA) in both groups, control and experimental, with levels significantly decreased in the group treated with melatonin after 15 and 60 min of high-intensity exercise, b) the total antioxidant activity (TAS) was lower in the control group than in the experimental, the latter showing significant differences at 60 min of high-intensity exercise c) the lipid profile of subjects in the experimental group showed lower triglyceride levels than the control group after 15 and 60 min of high-intensity exercise, d) immunological studies only showed, in the experimental group, an increase in IgA levels at 60 min after the exercise, and finally there were no significant differences between the groups for any of the other variables. In conclusion these results indicated that treatment with melatonin in acute sports exercise reversed oxidative stress, improved defenses and lipid metabolism, which would result in an improvement in fitness.
In the current survey, we summarize the published literature which supports the use of melatonin, an endogenously produced molecule, as a protective agent against chronic, low-level ionizing radiation. Under in vitro conditions, melatonin uniformly was found to protect cellular DNA and plasmid super coiled DNA from ionizing radiation damage due to Cs(137) or X-radiation exposure. Likewise, in an in vivo/in vitro study in which humans were given melatonin orally and then their blood lymphocytes were collected and exposed to Cs(137) ionizing radiation, nuclear DNA from the cells of those individuals who consumed melatonin (and had elevated blood levels) was less damaged than that from control individuals. In in vivo studies as well, melatonin given to animals prevented DNA and lipid damage (including limiting membrane rigidity) and reduced the percentage of animals that died when they had been exposed to Cs(137) or Co(60) radiation. Melatonin's ability to protect macromolecules from the damage inflicted by ionizing radiation likely stems from its high efficacy as a direct free radical scavenger and possibly also due to its ability to stimulate antioxidative enzymes. Melatonin is readily absorbed when taken orally or via any other route. Melatonin's ease of self administration and its virtual absence of toxicity or side effects, even when consumed over very long periods of time, are essential when large populations are exposed to lingering radioactive contamination such as occurs as a result of an inadvertent nuclear accident, an intentional nuclear explosion or the detonation of a radiological dispersion device, i.e., a "dirty" bomb.
Melatonin, an endogenously produced neurohormone secreted mainly by the pineal gland, has a variety of physiological functions and neuroprotective effects. Saturated fatty acids (SFAs) have been known to induce neurotoxicity and oxidative stress in central nervous system injuries and neurodegenerative pathologies. However, the effect of melatonin on SFAs-induced cytotoxicity in astroglial cells, if any, has remained to be explored. This study reports that in primary cultured astroglial cells, melatonin significantly attenuated palmitic acid (PA)-induced cytotoxicity in a concentration- and time-dependent manner. Additionally, melatonin effectively suppressed PA-induced reactive oxygen species generation and prevented PA-induced apoptosis whereby the rise in Bax/Bcl-2 ratio and caspase-3 activation in astroglial cells was inhibited. However, it did not appear to exert an obvious effect on PA-induced intracellular calcium overload. Luzindole, a nonselective melatonin receptor antagonist, attenuated melatonin's promotion effect of cell survival and Stat3 phosphorylation, indicating that melatonin exerts its protective property in astroglial cells, at least in part, through the activation of membrane receptors and then Stat3 signaling pathway. Finally, melatonin had an inhibitory effect on the pro-inflammatory cytokine gene expression. The results suggest that melatonin may be an effective cytoprotective agent against PA-based cytotoxicity through modulating cell survival and inflammatory response in astroglial cells.
In the present study, we aimed to examine the anti-atopic properties of bile from the cat fish, Silurus asotus, to determine its possible use as a pharmaceutical product.
The anti-atopic activities of cat fish bile were examined in a non-cell antioxidant, in-vitro assay (splenocytes and mast cells) and a 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis-like mouse model.
The results of these experiments revealed that Silurus asotus bile (SAB) scavenges radicals and protects proteins from superoxide attacks, suggesting that SAB suppresses the T helper (Th) type 2-skewed immune response. Th1/Th2 mRNA cytokines (interleukin (IL)-2, interferon (IFN)-γ and IL-4) from mouse splenocytes were effectively inhibited, and the release of β-hexosaminidase in RBL-2H3 mast cells was significantly suppressed by SAB. These results were supported by screening the Th1/Th2 cytokine mRNAs (IL-2, IFN-γ and IL-4) from lymph nodes in DNCB-treated mice. More dramatic results were observed in the histological changes at higher SAB concentrations (5%) compared to the therapeutic control, visualized using hematoxylin-eosin (H&E) staining.
The results presented in this study suggest that SAB may provide functional advantages with regard to treating atopic dermatitis because of its antioxidant and immune-suppressive effects.
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.
Singlet oxygen was generated by means of rose bengal under irradiation by visible light. N(1)-acetyl-5-methoxykynuramine (AMK) was rapidly destroyed by this reactive oxygen species, whereas its formylated precursor, N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK), was remarkably inert. At photon fluence rates of 1400 mumol photons/m(2)s, and using 20 mum rose bengal, most of initially 0.2 mm AMK was destroyed within 2 min, whereas AFMK remained practically unchanged for much longer periods of time. Competition experiments with other scavengers revealed the following order of reactivity towards singlet oxygen: diazabicyclo-[2,2,2]-octane (DABCO) < imidazole < 4-ethylphenol < N(alpha)-acetylhistidine < histidine < melatonin < AMK, the last one being about 150 times more effective than DABCO. Contrary to the oxidation in free radical-generating systems, AMK did not form adducts with the tyrosine side chain fragment, 4-ethylphenol, under the influence of singlet oxygen. In UV-exposed cells (keratinocytes, plant cells) it is likely to be more rapidly destroyed by singlet oxygen than formed from AFMK.
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.
Melatonin is a neurohormone produced by the pineal gland that regulates sleep and circadian functions. Melatonin also regulates inflammatory and immune processes acting as both an activator and inhibitor of these responses. Melatonin demonstrates endocrine, but also paracrine and autocrine effects in the leukocyte compartment: on one side, leukocytes respond to melatonin in a circadian fashion; on the other side, leukocytes are able to synthesize melatonin by themselves. With its endocrine and paracrine effects, melatonin differentially modulates pro-inflammatory enzymes, controls production of inflammatory mediators such as cytokines and leukotrienes and regulates the lifespan of leukocytes by interfering with apoptotic processes. Moreover, its potent antioxidant ability allows scavenging of oxidative stress in the inflamed tissues. The interesting timing of pro- and anti-inflammatory effects, such as those affecting lipoxygenase activity, suggests that melatonin might promote early phases of inflammation on one hand and contribute to its attenuation on the other hand, in order to avoid complications of chronic inflammation. This review aims at giving a comprehensive overview of the various inflammatory pathways regulated by this pleiotropic hormone.
Melatonin has been shown to inhibit the proliferation of malignant and transformed human prostate epithelial cells by transcriptional up-regulation of p27(Kip1) expression via MTNR1A receptor-mediated activation of protein kinase A (PKA) and protein kinase C (PKC) in parallel. Given that melatonin MTNR1A receptor is a G protein-coupled receptor, this study was conducted to identify the specific G proteins that mediate the antiproliferative action of melatonin on human prostate epithelial cells. In 22Rv1 and RWPE-1 cells, knockdown of either Gα(s) or Gα(q) , but not Gα(i2) expression by RNA interference, abrogated the effects of melatonin on p27(Kip1) and cell proliferation. Conversely, cellular overexpression of activated mutants of Gα(s) and Gα(q) in 22Rv1 and RWPE-1 cells mimicked the effects of melatonin on prostate epithelial cell antiproliferation by increasing p27(Kip1) expression through downstream activation of PKA and PKC in parallel. Moreover, melatonin or 2-iodomelatonin induced elevation of adenosine-3',5'-cyclic monophosphate (cAMP) in 22Rv1 and RWPE-1 cells. The effects of 2-iodomelatonin on cAMP were blocked by the nonselective MTNR1A/MTNR1B receptor antagonist luzindole but were not affected by the selective MTNR1B receptor antagonist 4-phenyl-2-propionamidotetraline (4-P-PDOT). Furthermore, knockdown of Gα(s) mitigated the stimulatory effects of 2-iodomelatonin on cAMP. Collectively, the data demonstrated, for the first time, functional coupling of MTNR1A receptor to Gα(s) in cancerous or transformed human cells expressing endogenous melatonin receptors. Our results also showed that dual activation of Gα(s) and Gα(q) proteins is involved in the signal transduction of MTNR1A receptor-mediated antiproliferative action of melatonin on human prostate epithelial cells.
Ageing is associated with an increased production of free radicals and alterations in the mechanisms of adaptation to oxidative stress. In fact, the free radical theory of ageing proposes that deleterious actions of free radicals are responsible for the functional deterioration associated with ageing. Moreover, a close relationship exists between calcium homeostasis and oxidative stress. The current work was aimed at proving that intracellular calcium overload induced by N-formyl-methionyl-leucyl-phenylalanine (FMLP) and/or thapsigargin leads to oxidative stress. We additionally examined the effect of melatonin on the levels of reactive oxygen species (ROS) and cell viability in human leucocytes collected from young (20-30-year-old) and elderly (65-75-year-old) individuals under both basal and oxidative stress-induced conditions. Treatments with 10 nM FMLP and/or 1 microM thapsigargin induced a transient increase in cytosolic free-calcium concentration ([Ca(2 + )](c)) in human leucocytes due to calcium release from internal stores, and led in turn to oxidative stress, as assessed by intracellular ROS measurement. Non-treated leucocytes from aged individuals exhibited higher ROS levels and lower rates of cell survival when compared to leucocytes from young individuals. Similar results were obtained in FMLP and/or thapsigargin-treated leucocytes from elderly individuals when compared to those from the young individuals. Melatonin treatment significantly reduced both hydrogen peroxide (H(2)O(2)) and superoxide anion levels, likely due to its free-radical scavenging properties, and enhanced leucocyte viability in both age groups. Therefore, melatonin may be a useful tool for the treatment of disease states and processes where an excessive production of oxidative damage occurs.
Melatonin is considered a promising antitumor agent, promoting apoptosis in tumor cells and contrasting it in normal cells. The basis for this selectivity is presumed to be the ability of melatonin to stimulate reactive oxygen species (ROS) production in tumor cells. Here we investigate the effect of melatonin on three types of human lymphocytes: normal blood lymphocytes, BL41 Burkitt lymphoma, and the cognate Epstein-Barr virus (EBV)-converted E2r. We found that melatonin promotes ROS production in all these cells. Melatonin protects BL41 from apoptosis in the same manner as normal lymphocytes, whereas E2r are unaffected. These results show that ROS production is not limited to tumor lymphocytes nor it is involved in apoptosis promotion; that melatonin does not promote apoptosis in tumor lymphocytes, but EBV inhibits melatonin anti-apoptotic effects; and that the anti-apoptotic effect of melatonin does not depend on the well-known chemical antioxidant properties of melatonin.
The RBL-2H3 cell line is a commonly used histamine-releasing cell line used in inflammation, allergy and immunological research. Quite commonly, it is referred to in research papers as a mast cell line, despite the fact that it is derived from basophils. There is also a lack of consistency, both between different research groups using the same cell line and with both mast cell and basophil physiology. The review follows the development of the RBL-2H3 cell line from its inception and then goes on to assess the nature of the cell line in terms of its characteristics and its response to various stimuli. The relationship of this cell line to the various mast cell subtypes and basophils is discussed and it is concluded that while the RBL-2H3 cell line shares some characteristics with both mast cells and basophils, it is not fully representative of either.
Melatonin acts both as a hormone of the pineal gland and as a local regulator molecule in various tissues. Quantities of total tissue melatonin exceed those released from the pineal. With regard to this dual role, to the orchestrating, systemic action on various target tissues, melatonin is highly pleiotropic. Numerous secondary effects result from the control of the circadian pacemaker and, in seasonal breeders, of the hypothalamic/pituitary hormonal axes. In mammals, various binding sites for melatonin have been identified, the membrane receptors MT(1) and MT(2), which are of utmost chronobiological importance, ROR and RZR isoforms as nuclear receptors from the retinoic acid receptor superfamily, quinone reductase 2, calmodulin, calreticulin, and mitochondrial binding sites. The G protein-coupled receptors (GPCRs) MT(1) and MT(2) are capable of parallel or alternate signaling via different Galpha subforms, in particular, Galpha(i) (2/) (3) and Galpha(q), and via Gbetagamma, as well. Multiple signaling can lead to the activation of different cascades and/or ion channels. Melatonin frequently decreases cAMP, but also activates phospholipase C and protein kinase C, acts via the MAP kinase and PI3 kinase/Akt pathways, modulates large conductance Ca(2+)-activated K(+) and voltage-gated Ca(2+) channels. MT(1) and MT(2) can form homo and heterodimers, and MT(1) interacts with other proteins in the plasma membrane, such as an orphan GPCR, GPR50, and the PDZ domain scaffolding protein MUPP1, effects which negatively or positively influence signaling capacity. Cross-talks between different signaling pathways, including influences of the membrane receptors on nuclear binding sites, are discussed. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.
Through inhibitory G protein-coupled melatonin receptors, melatonin regulates intracellular signaling systems and also the transcriptional activity of certain genes. Clock genes are proposed as regulatory factors in forming dopamine-related behaviors and mood and melatonin has the ability to regulate these processes. Melatonin-mediated changes in clock gene expression have been reported in brain regions, including the striatum, that are crucial for the development of dopaminergic behaviors and mood. However, it is not known whether melatonin receptors present in striatum mediate these effects. Therefore, we investigated the role of the melatonin/melatonin receptor system on clock gene expression using a model of primary neuronal cultures prepared from striatum. We found that melatonin at the receptor affinity range (i.e., nm) affects the expression of the clock genes mPer1, mClock, mBmal1 and mNPAS2 (neuronal PAS domain protein 2) differentially in a pertussis toxin-sensitive manner: a decrease in Per1 and Clock, an increase in NPAS2 and no change in Bmal1 expression. Furthermore, mutating MT1 melatonin receptor (i.e., MT1 knockouts, MT1(-/-)) reversed melatonin-induced changes, indicating the involvement of MT1 receptor in the regulatory action of melatonin on neuronal clock gene expression. Therefore, by controlling clock gene expression we propose melatonin receptors (i.e., MT1) as novel therapeutic targets for the pathobiologies of dopamine-related behaviors and mood.
Shida CS, Castrucci AML, Lamy-Freund MT. High melatonin solubility in aqueous medium. J Pineal Res. 1994:16:198–201.
The pineal hormone melatonin (5-methoxy-N-acetyl-tryptamine) has been reported to participate in important physiological processes. Although some of its biological actions seem to depend on a protein receptor at the membrane surface, melatonin is known to interact with a large variety of tissues and cells, suggesting that the molecule may not necessarily interact through a specific membrane receptor at a specific cell. Most discussions of melatonin activity have assumed that the molecule is highly hydrophobic. Contrary to belief, the present work shows that melatonin is soluble in a purely aqueous medium up to 5 ± 10-3 M and describes a new method of melatonin preparation which shows the high hydrophilicity of the molecule. The results presented will affect the current biological hypothesis on the need of a melatonin carrier in the blood stream or the mechanisms which allow the hormone to cross the cell membrane and interact at the level of the nucleus.
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Considering the widespread actions of the pineal hormone melatonin in vertebrate organisms, it is remarkable that so few biomedical scientists took the pineal gland seriously until only recently. When melatonin (N-acetyl-5-methoxytryptamine) was discovered in 1958, Lerner and colleagues (1) hoped that it would be a treatment for irregular skin pigmentation that occurs in humans with certain diseases. This action of melatonin in humans has proven unproductive although in non-mammalian vertebrates an association of melatonin with dermal melanophores is well documented (2).
Within a decade of its discovery, melatonin had been shown to be functionally related to neuroendocrine physiology, with the most obvious link being its control of reproductive physiology in photoperiodic rodents (3). By 1972, a scheme defining the role of the pineal gland, seasonally changing photoperiods and annual fluctuations in reproductive competence had been presented (4). These studies were the basis of later tests on the contraceptive potential
The interaction of melatonin with water containing either sodium bis (2-ethylhexyl) sulfosuccinate (AOT) or soybean phosphatidylcholine (lecithin) reversed micelles has been investigated by UV absorption spectroscopy, at a molar ratio of melatonin:surfactant 1:800 for AOT and 1:400 for lecithin reversed micelles, and by varying the water:surfactant molar ratio (R). Our results suggest that in the presence of domains from apolar organic solvent to surfactant and to water, melatonin positions itself in the micellar phase, with a preferential location in the surfactant polar head group domain, independent of the nature of the surfactant and the amount of water encapsulated into the micellar core. Effects are due to the hydrophilic and lipophilic moieties of melatonin. The effectiveness of melatonin as an electron donor and free radical scavenger has been recently recognized. While supporting the hypothesis that melatonin may provide antioxidant protection without the benefit of receptors, present findings may suggest that the molecule could easily scavenge aqueous as well as lipophilic radicals.
Antioxidant enzymes form the first line of defense against free radicals in organisms. Their regulation depends mainly on the oxidant status of the cell, given that oxidants are their principal modulators. However, other factors have been reported to increase antioxidant enzyme activity and/or gene expression. During the last decade, the antioxidant melatonin has been shown to possess genomic actions, regulating the expression of several genes. Melatonin also influences both antioxidant enzyme activity and cellular mRNA levels for these enzymes. In the present report, we review the studies which document the influence of melatonin on the activity and expression of the antioxidative enzymes glutathione peroxidase, superoxide dismutases and catalase both under physiological and under conditions of elevated oxidative stress. We also analyze the possible mechanisms by which melatonin regulates these enzymes.
Activation of mast cells by lipopolysaccharide (LPS) results in the production of TNF-alpha and IL-13. TNF-alpha and IL-13 are key mediators in the development of neutrophilic and allergic inflammation, respectively. LPS-induced TNF-alpha and IL-13 production in mast cells has been reported to be mediated by Toll-like receptor 4 (TLR4) signalling, but differences in signal transduction mechanisms leading to the production of these cytokines are not clearly defined.
We investigated the molecular mechanisms responsible for LPS-induced TNF-alpha and IL-13 production in mast cells.
TNF-alpha and IL-13 production by LPS was assessed by transfecting RBL-2H3 cells with dominant-negative (DN) expression vectors.
Transfection of RBL-2H3 cells with plasmids encoding DN mutants of myeloid differentiation protein (MyD88) and TNFR-associated factor (TRAF6) inhibited both LPS-induced TNF-alpha and IL-13 production. IkappaBalpha-DN inhibited LPS-induced production of TNF-alpha, but not IL-13. We also found that inhibition of p38 kinase suppressed both TNF-alpha and IL-13 induction by LPS, and inhibition of JNK reduced IL-13 production, but not TNF-alpha. Furthermore, we found that protein kinase R (PKR) was activated by LPS in these cells. Treatment with 2-aminopurine, a PKR inhibitor, attenuated LPS-induced nuclear factor-kappaB activation and TNF-alpha production, whereas inhibition of PKR had little effect on IL-13 production.
These findings indicate that the production of TNF-alpha and IL-13 by LPS required TLR4/MyD88/TRAF6 signalling as a common pathway of mast cell-mediated inflammation. We furthermore found that TNF-alpha and IL-13 production were differentially regulated by signalling cascades through PKR and mitogen-activated protein kinases downstream of TRAF6 in mast cells.
Three-dimensional homology models of human MT(1) and MT(2) melatonin receptors were built with the aim to investigate the structure-activity relationships (SARs) of MT(2) selective antagonists. A common interaction pattern was proposed for a series of structurally different MT(2) selective antagonists, which were positioned within the binding site by docking and simulated annealing. The proposed antagonist binding mode to the MT(2) receptor is characterized by the accommodation of the out-of-plane substituents in a hydrophobic pocket, which resulted as being fundamental for the explanation of the antagonist behavior and the MT(2) receptor selectivity. Moreover, to assess the ability of the MT(2) receptor model to reproduce the SARs of MT(2) antagonists, three new derivatives of the MT(2) selective antagonist N-[1-(4-chloro-benzyl)-4-methoxy-1H-indol-2-ylmethyl]-propionamide (7) were synthesized and tested for their receptor affinity and intrinsic activity. These compounds were docked into the MT(2) receptor model and were submitted to molecular dynamics studies, providing results in qualitative agreement with the experimental data. These results confirm the importance of the out-of-plane group in receptor binding and selectivity and provide a partial validation of the proposed G protein-coupled receptor model.
Pollenosis is a disease that affects 1 in 10 of the Japanese population. During the season of cedar pollen dispersal, many patients suffer from symptoms such as sniffling, sternutation, and itching of the eyes. Japanese butterbur is a popular vegetable and is one of the few domestic vegetables in Japan. The anti type I allergic effects of an aqueous ethanol extract from aerial parts of Japanese butterbur (JBE) were evaluated in rats and RBL-2H3 mast cells. In the passive cutaneous anaphylaxis reaction in rats, a single oral treatment of JBE (1000 mg/kg) was found to suppress the reaction. In IgE-sensitized RBL-2H3 cells, JBE (10-100 microg/mL) inhibited beta-hexosaminidase release, leukotriene C(4)/D(4)/E(4) synthesis, and TNF-alpha production. Moreover, a high concentration of JBE (1000 microg/mL) suppressed smooth muscle constriction induced by histamine (10 microM) and leukotriene D(4) (10 nM) in a guinea pig trachea strip. The search for components in JBE with an inhibitory activity on mast cell degranulation was guided by inhibition of beta-hexsosaminidase release. Two eremophilane-type sesquiterpenes, six polyphenolic compounds, and two triterpene glycosides were isolated. Of these compounds, fukinolic acid, a principal polyphenol constituent, showed potent inhibitory activity (IC(50) value = 2.1 microg/mL). Consequently, On the basis of its inhibition of mast cell activation and direct smooth muscle reaction induced by released mediators, JBE was found to suppress the type I allergic reaction.
Melatonin is a highly conserved molecule. Its presence can be traced back to ancient photosynthetic prokaryotes. A primitive and primary function of melatonin is that it acts as a receptor-independent free radical scavenger and a broad-spectrum antioxidant. The receptor-dependent functions of melatonin were subsequently acquired during evolution. In the current review, we focus on melatonin metabolism which includes the synthetic rate-limiting enzymes, synthetic sites, potential regulatory mechanisms, bioavailability in humans, mechanisms of breakdown and functions of its metabolites. Recent evidence indicates that the original melatonin metabolite may be N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) rather than its commonly measured urinary excretory product 6-hydroxymelatonin sulfate. Numerous pathways for AFMK formation have been identified both in vitro and in vivo. These include enzymatic and pseudo-enzymatic pathways, interactions with reactive oxygen species (ROS)/reactive nitrogen species (RNS) and with ultraviolet irradiation. AFMK is present in mammals including humans, and is the only detectable melatonin metabolite in unicellular organisms and metazoans. 6-hydroxymelatonin sulfate has not been observed in these low evolutionary-ranked organisms. This implies that AFMK evolved earlier in evolution than 6-hydroxymelatonin sulfate as a melatonin metabolite. Via the AFMK pathway, a single melatonin molecule is reported to scavenge up to 10 ROS/RNS. That the free radical scavenging capacity of melatonin extends to its secondary, tertiary and quaternary metabolites is now documented. It appears that melatonin's interaction with ROS/RNS is a prolonged process that involves many of its derivatives. The process by which melatonin and its metabolites successively scavenge ROS/RNS is referred as the free radical scavenging cascade. This cascade reaction is a novel property of melatonin and explains how it differs from other conventional antioxidants. This cascade reaction makes melatonin highly effective, even at low concentrations, in protecting organisms from oxidative stress. In accordance with its protective function, substantial amounts of melatonin are found in tissues and organs which are frequently exposed to the hostile environmental insults such as the gut and skin or organs which have high oxygen consumption such as the brain. In addition, melatonin production may be upregulated by low intensity stressors such as dietary restriction in rats and exercise in humans. Intensive oxidative stress results in a rapid drop of circulating melatonin levels. This melatonin decline is not related to its reduced synthesis but to its rapid consumption, i.e. circulating melatonin is rapidly metabolized by interaction with ROS/RNS induced by stress. Rapid melatonin consumption during elevated stress may serve as a protective mechanism of organisms in which melatonin is used as a first-line defensive molecule against oxidative damage. The oxidative status of organisms modifies melatonin metabolism. It has been reported that the higher the oxidative state, the more AFMK is produced. The ratio of AFMK and another melatonin metabolite, cyclic 3-hydroxymelatonin, may serve as an indicator of the level of oxidative stress in organisms.
Craniocerebral trauma (CCT) is the most frequent cause of morbidity-mortality as a result of an accident. The probable origins and etiologies are multifactorial and include free radical formation and oxidative stress, the suppression of nonspecific resistance, lymphocytopenia (disorder in the adhesion and activation of cells), opportunistic infections, regional macro and microcirculatory alterations, disruptive sleep-wake cycles and toxicity caused by therapeutic agents. These pathogenic factors contribute to the unfavorable development of clinical symptoms as the disease progresses. Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine endogenously produced in the pineal gland and in other organs and it is protective agent against damage following CCT. Some of the actions of melatonin that support its pharmacological use after CCT include its role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes (e.g. superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase), inhibition of pro-inflammatory cytokines and activation-adhesion molecules which consequently reduces lymphocytopenia and infections by opportunistic organisms. The chronobiotic capacity of melatonin may also reset the natural circadian rhythm of sleep and wakefulness. Melatonin reduces the toxicity of the drugs used in the treatment of CCT and increases their efficacy. Finally, melatonin crosses the blood-brain barrier and reduces contusion volume and stabilizes cellular membranes preventing vasospasm and apoptosis of endothelial cells that occurs as a result of CCT.
Among the non-neurological functions of melatonin, much attention is being directed to the ability of melatonin to modulate the immune system, whose cells possess melatonin-specific receptors and biosynthetic enzymes. Melatonin controls cell behaviour by eliciting specific signal transduction actions after its interaction with plasma membrane receptors (MT(1), MT(2)); additionally, melatonin potently neutralizes free radicals. Melatonin regulates immune cell loss by antagonizing apoptosis. A major unsolved question is whether this is due to receptor involvement, or to radical scavenging considering that apoptosis is often dependent on oxidative alterations. Here, we provide evidence that on U937 monocytic cells, apoptosis is antagonized by melatonin by receptor interaction rather than by radical scavenging. First, melatonin and a set of synthetic analogues prevented apoptosis in a manner that is proportional to their affinity for plasma membrane receptors but not to their antioxidant ability. Secondly, melatonin's antiapoptotic effect required key signal transduction events including G protein, phospholipase C and Ca(2+) influx and, more important, it is sensitive to the specific melatonin receptor antagonist luzindole.
- R R Rich
- T A Fleisher
- W T Shearer
Rich, R.R., Fleisher, T.A., Shearer, W.T., 2008. Clinical Immunology Principles and Practices, 3rd ed. Elsevier, USA.
Nuclear localization of melatonin in different mammalian tissues: immunocytochemical and radioimmunoassay evidence
- A Menendez-Pelaez
- B Poeggeler
- R J Reiter
- L Barlow-Walden
- M I Pablos
- D X Tan
Menendez-Pelaez, A., Poeggeler, B., Reiter, R.J., Barlow-Walden, L., Pablos, M.I., Tan,
D.X., 1993. Nuclear localization of melatonin in different mammalian tissues: immunocytochemical and radioimmunoassay evidence. J. Cell. Biochem. 53, 373-382.
Protective effects of melatonin and s-methylisothiourea on mechlorethamine induced nephrotoxicity
- Z I Kunak
- E Macit
- H Yaren
- H Yaman
- E Fakir
- I Aydin
- T Turker
- Y G Kurt
- A Ozcan
- B Uysal
- S Isbilir
- E O Akgul
- T Cayci
- A Korkmaz
- L Kenar
Kunak, Z.I., Macit, E., Yaren, H., Yaman, H., Fakir, E., Aydin, I., Turker, T., Kurt, Y.G.,
Ozcan, A., Uysal, B., Isbilir, S., Akgul, E.O., Cayci, T., Korkmaz, A., Kenar, L., 2012. Protective effects of melatonin and s-methylisothiourea on mechlorethamine induced
nephrotoxicity. J. Surg. Res. 175, 17-23.