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Ng MG, Ng KY, Koh RY, Chye SM. Potential role of melatonin in prevention and treatment of leukaemia. Horm Mol Biol Clin Investig 2021; 42:445-461. [PMID: 34355548 DOI: 10.1515/hmbci-2021-0009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 07/06/2021] [Indexed: 11/15/2022]
Abstract
Leukaemia is a haematological malignancy originated from the bone marrow. Studies have shown that shift work could disrupt the melatonin secretion and eventually increase leukaemia incidence risk. Melatonin, a pineal hormone, has shown promising oncostatic properties on a wide range of cancers, including leukaemia. We first reviewed the relationship between shift work and the incidence rate of leukaemia and then discussed the role of melatonin receptors (MT1 and MT2) and their functions in leukaemia. Moreover, the connection between inflammation and leukaemia, and melatonin-induced anti-leukaemia mechanisms including anti-proliferation, apoptosis induction and immunomodulation are comprehensively discussed. Apart from that, the synergistic effects of melatonin with other anticancer compounds are also included. In short, this review article has compiled the evidence of anti-leukaemia properties displayed by melatonin and discuss its potential to act as adjunct for anti-leukaemia treatment. This review may serve as a reference for future studies or experimental research to explore the possibility of melatonin serving as a novel therapeutic agent for leukaemia.
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Affiliation(s)
- Ming Guan Ng
- School of Health Science, International Medical University, Kuala Lumpur, Malaysia
| | - Khuen Yen Ng
- School of Pharmacy, Monash University Malaysia, Selangor, Malaysia
| | - Rhun Yian Koh
- Division of Biomedical Science and Biotechnology, School of Health Science, International Medical University, Kuala Lumpur, Malaysia
| | - Soi Moi Chye
- Division of Biomedical Science and Biotechnology, School of Health Science, International Medical University, Kuala Lumpur, Malaysia
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2
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Wang J, Zhuo Z, Ma X, Liu Y, Xu J, He C, Fu Y, Wang F, Ji P, Zhang L, Liu G. Melatonin Alleviates the Suppressive Effect of Hypoxanthine on Oocyte Nuclear Maturation and Restores Meiosis via the Melatonin Receptor 1 (MT1)-Mediated Pathway. Front Cell Dev Biol 2021; 9:648148. [PMID: 33937242 PMCID: PMC8083900 DOI: 10.3389/fcell.2021.648148] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 03/17/2021] [Indexed: 01/12/2023] Open
Abstract
It is well known that hypoxanthine (HX) inhibits nuclear maturation of oocytes by elevating the intracellular cAMP level, while melatonin (MT) is a molecule that reduces cAMP production, which may physiologically antagonize this inhibition and restore the meiosis process. We conducted in vitro and in vivo studies to examine this hypothesis. The results showed that 10-3 M MT potentiated the inhibitory effect of HX on mouse oocyte meiosis by lowering the rate of germinal vesicle breakdown (GVBD) and the first polar body (PB1). However, 10-5 M and 10-7 M MT significantly alleviated the nuclear suppression induced by HX and restored meiosis in 3- and 6-week-old mouse oocytes, respectively. We identified that the rate-limiting melatonin synthetic enzyme AANAT and melatonin membrane receptor MT1 were both expressed in oocytes and cumulus cells at the GV and MII stages. Luzindole, a non-selective melatonin membrane receptor antagonist, blocked the activity of MT on oocyte meiotic recovery (P < 0.05). This observation indicated that the activity of melatonin was mediated by the MT1 receptor. To understand the molecular mechanism further, MT1 knockout (KO) mice were constructed. In this MT1 KO animal model, the PB1 rate was significantly reduced with the excessive expression of cAPM synthases (Adcy2, Adcy6, Adcy7, and Adcy9) in the ovaries of these animals. The mRNA levels of Nppc and Npr2 were upregulated while the genes related to progesterone synthesis (Cyp11a11), cholesterol biosynthesis (Insig1), and feedback (Lhcgr, Prlr, and Atg7) were downregulated in the granulosa cells of MT1 KO mice (P < 0.05). The altered gene expression may be attributed to the suppression of oocyte maturation. In summary, melatonin protects against nuclear inhibition caused by HX and restores oocyte meiosis via MT1 by reducing the intracellular concentration of cAMP.
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Affiliation(s)
- Jing Wang
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Zhiyong Zhuo
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China.,Beijing Keao Xieli Feed Co., Ltd., Beijing, China
| | - Xiao Ma
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yunjie Liu
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Jing Xu
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Changjiu He
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yao Fu
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Feng Wang
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Pengyun Ji
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Lu Zhang
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Guoshi Liu
- Beijing Key Laboratory of Animal Genetic Improvement, Key Laboratory of Animal Genetics and Breeding of the Ministry of Agriculture, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
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Ferreira MA, Azevedo H, Mascarello A, Segretti ND, Russo E, Russo V, Guimarães CRW. Discovery of ACH-000143: A Novel Potent and Peripherally Preferred Melatonin Receptor Agonist that Reduces Liver Triglycerides and Steatosis in Diet-Induced Obese Rats. J Med Chem 2021; 64:1904-1929. [PMID: 33626870 DOI: 10.1021/acs.jmedchem.0c00627] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The modulation of melatonin signaling in peripheral tissues holds promise for treating metabolic diseases like obesity, diabetes, and nonalcoholic steatohepatitis. Here, several benzimidazole derivatives have been identified as novel agonists of the melatonin receptors MT1 and MT2. The lead compounds 10b, 15a, and 19a demonstrated subnanomolar potency at MT1/MT2 receptors, high oral bioavailability in rodents, peripherally preferred exposure, and excellent selectivity in a broad panel of targets. Two-month oral administration of 10b in high-fat diet rats led to a reduction in body weight gain similar to dapagliflozin with superior results on hepatic steatosis and triglyceride levels. An early toxicological assessment indicated that 10b (also codified as ACH-000143) was devoid of hERG binding, genotoxicity, and behavioral alterations at doses up to 100 mg/kg p.o., supporting further investigation of this compound as a drug candidate.
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Affiliation(s)
| | - Hatylas Azevedo
- Aché Laboratórios Farmacêuticos, Guarulhos, São Paulo 07034-904, Brazil
| | | | | | - Elisa Russo
- Zirkon Ind. Com de Insumos Químicos, Itapira, São Paulo 13977-105, Brazil
| | - Valter Russo
- Zirkon Ind. Com de Insumos Químicos, Itapira, São Paulo 13977-105, Brazil
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4
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Noseda ACD, Rodrigues LS, Targa ADS, Ilkiw JL, Fagotti J, Dos Santos PD, Cecon E, Markus RP, Solimena M, Jockers R, Lima MMS. MT 2 melatonin receptors expressed in the olfactory bulb modulate depressive-like behavior and olfaction in the 6-OHDA model of Parkinson's disease. Eur J Pharmacol 2021; 891:173722. [PMID: 33159932 DOI: 10.1016/j.ejphar.2020.173722] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 10/27/2020] [Accepted: 11/01/2020] [Indexed: 12/26/2022]
Abstract
Melatonin MT1 and MT2 receptors are expressed in the glomerular layer of the olfactory bulb (OB); however, the role of these receptors has not been evaluated until now. Considering the association of the OB with olfactory and depressive disorders in Parkinson's disease (PD), we sought to investigate the involvement of melatonin receptors in these non-motor disturbances in an intranigral 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD. We demonstrate the presence of functional melatonin receptors in dopaminergic neurons of the glomerular layer. Local administration of melatonin (MLT, 1 μg/μl), luzindole (LUZ, 5 μg/μl) or the MT2-selective receptor drug 4-P-PDOT (5 μg/μl) reversed the depressive-like behavior elicited by 6-OHDA. Sequential administration of 4-P-PDOT and MLT (5 μg/μl, 1 μg/μl) promoted additive antidepressant-like effects. In the evaluation of olfactory discrimination, LUZ induced an olfactory impairment when associated with the nigral lesion-induced impairment. Thus, our results suggest that melatonin MT2 receptors expressed in the glomerular layer are involved in depressive-like behaviors and in olfactory function associated with PD.
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Affiliation(s)
- Ana Carolina D Noseda
- Department of Physiology, Federal University of Paraná, Curitiba, PR, Brazil; Department of Pharmacology, Federal University of Paraná, Curitiba, PR, Brazil
| | - Lais S Rodrigues
- Department of Physiology, Federal University of Paraná, Curitiba, PR, Brazil; Department of Pharmacology, Federal University of Paraná, Curitiba, PR, Brazil
| | - Adriano D S Targa
- Department of Physiology, Federal University of Paraná, Curitiba, PR, Brazil; Department of Pharmacology, Federal University of Paraná, Curitiba, PR, Brazil; Translational Research in Respiratory Medicine, Hospital Universitari Arnau de Vilanova-Santa Maria, IRBLleida, Lleida, Spain; Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Madrid, Spain
| | - Jessica L Ilkiw
- Department of Physiology, Federal University of Paraná, Curitiba, PR, Brazil
| | - Juliane Fagotti
- Department of Physiology, Federal University of Paraná, Curitiba, PR, Brazil
| | | | - Erika Cecon
- Université de Paris, Institut Cochin, INSERM, CNRS, F-75014 Paris, France
| | - Regina P Markus
- Department of Physiology, Institute of Bioscience, University of São Paulo, São Paulo, Brazil
| | - Michele Solimena
- Paul Langerhans Institute Dresden (PLID) of the Helmholtz Center Munich at the University Hospital Carl Gustav Carus and Faculty of Medicine of the TU Dresden, Dresden, Germany; German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany
| | - Ralf Jockers
- Université de Paris, Institut Cochin, INSERM, CNRS, F-75014 Paris, France
| | - Marcelo M S Lima
- Department of Physiology, Federal University of Paraná, Curitiba, PR, Brazil; Department of Pharmacology, Federal University of Paraná, Curitiba, PR, Brazil.
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Parvataneni T, Srinivas S, Shah K, Patel RS. Perspective on Melatonin Use for Sleep Problems in Autism and Attention-Deficit Hyperactivity Disorder: A Systematic Review of Randomized Clinical Trials. Cureus 2020; 12:e8335. [PMID: 32617211 PMCID: PMC7325410 DOI: 10.7759/cureus.8335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Melatonin is a hormone produced by the pineal gland and is available over the counter for treating sleep problems in the pediatric population. We conducted a systematic review of randomized clinical trials (RCTs) on MEDLINE and included six studies that met our inclusion criteria. RCTs were conducted in patients from two to 18 years of age with a diagnostic and statistical manual of mental disorders (DSM)-IV diagnosis of autism spectrum disease (ASD) and/or attention-deficit hyperactivity disorder (ADHD) in both short-term and long-term RCTs ranging from eight-week to 52-week studies. The mean difference in the children’s sleep disorder showed statistically significant improvement in sleep duration and sleep latency onset compared to the placebo. Overall, a high response rate was observed in the melatonin group compared to the placebo in treating sleep problems in children. Melatonin is a well-tolerated and safe medication in the dose range of 2-10 mg/day in the child and adolescent population.
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Affiliation(s)
- Tarun Parvataneni
- Psychiatry, Siddavanahalli Nijalingappa Medical College and HSK Hospital and Research Centre, Bagalkot, IND
| | - Sushma Srinivas
- Psychiatry, A.J. Institute of Medical Sciences and Research Centre, Mangalore, IND
| | - Kaushal Shah
- Psychiatry, Griffin Memorial Hospital, Norman, USA
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6
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Liu YJ, Ji DM, Liu ZB, Wang TJ, Xie FF, Zhang ZG, Wei ZL, Zhou P, Cao YX. Melatonin maintains mitochondrial membrane potential and decreases excessive intracellular Ca 2+ levels in immature human oocytes. Life Sci 2019; 235:116810. [PMID: 31472147 DOI: 10.1016/j.lfs.2019.116810] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 12/14/2022]
Abstract
AIMS Previous reports have demonstrated that melatonin exists in multiple extrapineal sites, and higher amounts of melatonin are present in human follicular fluid than in serum, which indicates that it might play key roles in human oocyte maturation and subsequent embryonic development. Melatonin has been shown to be a potent antioxidant and might be beneficial to human oocytes during in vitro maturation (IVM). However, the underlying mechanisms of melatonin action during IVM have not been thoroughly investigated. MAIN METHODS Immunofluorescence staining, western blotting, and ELISA were applied to investigate whether melatoninergic components are expressed in the cultured human ovarian cumulus cells. TMRE staining and Fluo-4 AM staining were performed to detect the mitochondrial membrane potential and intracellular Ca2+ levels of immature human oocytes respectively. KEY FINDINGS First, cultured human ovary cumulus cells synthesized melatonin in vitro, and it expressed serotonin (the precursor of melatonin) and the two key enzymes, i.e. N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT). Additionally, the results suggest that melatonin maintains the mitochondrial membrane potential and decrease excessive Ca2+ levels in immature human oocytes during IVM. SIGNIFICANCE In conclusion, we provide evidence that the melatoninergic components were expressed in cultured human ovarian cumulus cells, and melatonin might reduce oxidative stress of human oocytes by ameliorating mitochondrial function. In view of the significant clinical value that immature human oocytes have in assisted reproductive technology (ART), our findings highlight a potential treatment strategy of using melatonin to improve mitochondrial function and to enhance the quality of human oocytes during IVM.
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Affiliation(s)
- Ya-Jing Liu
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China.
| | - Dong-Mei Ji
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China
| | - Zhen-Bang Liu
- School of Life Sciences, University of Science and Technology of China, Hefei 230027, Anhui, PR China
| | - Tian-Juan Wang
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China
| | - Fen-Fen Xie
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China
| | - Zhi-Guo Zhang
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China
| | - Zhao-Lian Wei
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China
| | - Ping Zhou
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China
| | - Yun-Xia Cao
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Anhui Medical University, Anhui Province Key Laboratory of Reproductive Health and Genetics, Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, PR China.
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Abstract
Despite considerable advances in the past few years, obesity and type 2 diabetes mellitus (T2DM) remain two major challenges for public health systems globally. In the past 9 years, genome-wide association studies (GWAS) have established a major role for genetic variation within the MTNR1B locus in regulating fasting plasma levels of glucose and in affecting the risk of T2DM. This discovery generated a major interest in the melatonergic system, in particular the melatonin MT2 receptor (which is encoded by MTNR1B). In this Review, we discuss the effect of melatonin and its receptors on glucose homeostasis, obesity and T2DM. Preclinical and clinical post-GWAS evidence of frequent and rare variants of the MTNR1B locus confirmed its importance in regulating glucose homeostasis and T2DM risk with minor effects on obesity. However, these studies did not solve the question of whether melatonin is beneficial or detrimental, an issue that will be discussed in the context of the peculiarities of the melatonergic system. Melatonin receptors might have therapeutic potential as they belong to the highly druggable G protein-coupled receptor superfamily. Clarifying the precise role of melatonin and its receptors on glucose homeostasis is urgent, as melatonin is widely used for other indications, either as a prescribed medication or as a supplement without medical prescription, in many countries in Europe and in the USA.
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Affiliation(s)
- Angeliki Karamitri
- Inserm, U1016, Institut Cochin, Paris, France
- CNRS UMR 8104, Paris, France
- Université Paris Descartes, Université Sorbonne Paris Cité, Paris, France
| | - Ralf Jockers
- Inserm, U1016, Institut Cochin, Paris, France.
- CNRS UMR 8104, Paris, France.
- Université Paris Descartes, Université Sorbonne Paris Cité, Paris, France.
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Amaral FGD, Cipolla-Neto J. A brief review about melatonin, a pineal hormone. ARCHIVES OF ENDOCRINOLOGY AND METABOLISM 2018; 62:472-479. [PMID: 30304113 PMCID: PMC10118741 DOI: 10.20945/2359-3997000000066] [Citation(s) in RCA: 190] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 08/31/2018] [Indexed: 11/23/2022]
Abstract
Melatonin is a ubiquitous molecule in nature, being locally synthesized in several cells and tissues, besides being a hormone that is centrally produced in the pineal gland of vertebrates, particularly in mammals. Its pineal synthesis is timed by the suprachiasmatic nucleus, that is synchronized to the light-dark cycle via the retinohypothalamic tract, placing melatonin synthesis at night, provided its dark. This unique trait turns melatonin into an internal synchronizer that adequately times the organism's physiology to the daily and seasonal demands. Besides being amphiphilic, melatonin presents specific mechanisms and ways of action devoted to its role as a time-giving agent, being widely spread in the organism. The present review aims to focus on melatonin as a pineal hormone with specific mechanisms and ways of action, besides presenting the clinical syndromes related to its synthesis and/or function disruptions.
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Affiliation(s)
| | - José Cipolla-Neto
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo (USP), São Paulo, SP, Brasil
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Cipolla-Neto J, Amaral FGD. Melatonin as a Hormone: New Physiological and Clinical Insights. Endocr Rev 2018; 39:990-1028. [PMID: 30215696 DOI: 10.1210/er.2018-00084] [Citation(s) in RCA: 318] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 06/21/2018] [Indexed: 02/07/2023]
Abstract
Melatonin is a ubiquitous molecule present in almost every live being from bacteria to humans. In vertebrates, besides being produced in peripheral tissues and acting as an autocrine and paracrine signal, melatonin is centrally synthetized by a neuroendocrine organ, the pineal gland. Independently of the considered species, pineal hormone melatonin is always produced during the night and its production and secretory episode duration are directly dependent on the length of the night. As its production is tightly linked to the light/dark cycle, melatonin main hormonal systemic integrative action is to coordinate behavioral and physiological adaptations to the environmental geophysical day and season. The circadian signal is dependent on its daily production regularity, on the contrast between day and night concentrations, and on specially developed ways of action. During its daily secretory episode, melatonin coordinates the night adaptive physiology through immediate effects and primes the day adaptive responses through prospective effects that will only appear at daytime, when melatonin is absent. Similarly, the annual history of the daily melatonin secretory episode duration primes the central nervous/endocrine system to the seasons to come. Remarkably, maternal melatonin programs the fetuses' behavior and physiology to cope with the environmental light/dark cycle and season after birth. These unique ways of action turn melatonin into a biological time-domain-acting molecule. The present review focuses on the above considerations, proposes a putative classification of clinical melatonin dysfunctions, and discusses general guidelines to the therapeutic use of melatonin.
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Affiliation(s)
- José Cipolla-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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10
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Lochner A, Marais E, Huisamen B. Melatonin and cardioprotection against ischaemia/reperfusion injury: What's new? A review. J Pineal Res 2018; 65:e12490. [PMID: 29570845 DOI: 10.1111/jpi.12490] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 03/01/2018] [Indexed: 12/20/2022]
Abstract
Melatonin is a pleiotropic hormone with several functions. It binds to specific receptors and to a number of cytosolic proteins, activating a vast array of signalling pathways. Its potential to protect the heart against ischaemia/reperfusion damage has attracted much attention, particularly in view of its possible clinical applications. This review will focus mainly on the possible signalling pathways involved in melatonin-induced cardioprotection. In particular, the role of the melatonin receptors and events downstream of receptor activation, for example, the reperfusion injury salvage kinase (RISK), survivor activating factor enhancement (SAFE) and Notch pathways, the sirtuins, nuclear factor E2-related factor 2 (Nrf2) and translocases in the outer membrane (TOM70) will be discussed. Particular attention is given to the role of the mitochondrion in melatonin-induced cardioprotection. In addition, a brief overview will be given regarding the status quo of the clinical application of melatonin in humans.
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Affiliation(s)
- Amanda Lochner
- Division of Medical Physiology, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Tygerberg, South Africa
| | - Erna Marais
- Division of Medical Physiology, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Tygerberg, South Africa
| | - Barbara Huisamen
- Biomedical Research and Innovation Platform, SA Medical Research Council, Tygerberg, South Africa
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11
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Ramírez-Reveco A, Villarroel-Espíndola F, Rodríguez-Gil JE, Concha II. Neuronal signaling repertoire in the mammalian sperm functionality. Biol Reprod 2017; 96:505-524. [PMID: 28339693 DOI: 10.1095/biolreprod.116.144154] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/24/2017] [Indexed: 12/14/2022] Open
Abstract
The common embryonic origin has been a recurrent explanation to understand the presence of "neural receptors" in sperm. However, this designation has conditioned a bias marked by the classical neurotransmission model, dismissing the possibility that neurotransmitters can play specific roles in the sperm function by themselves. For instance, the launching of acrosome reaction, a fundamental sperm function, includes several steps that recall the process of presynaptic secretion. Unlike of postsynaptic neuron, whose activation is mediated by molecular interaction between neurotransmitter and postsynaptic receptors, the oocyte activation is not mediated by receptors, but by cytosolic translocation of sperm phospholipase (PLCζ). Thus, the sperm has a cellular design to access and activate the oocyte and restore the ploidy of the species by an "allogenic pronuclear fusion." At subcellular level, the events controlling sperm function, particularly the capacitation process, are activated by chemical signals that trigger ion fluxes, sterol oxidation, synthesis of cyclic adenosine monophosphate, protein kinase A activation, tyrosine phosphorylations and calcium signaling, which correspond to second messengers similar to those associated with exocytosis and growth cone guidance in neurons. Classically, the sperm function associated with neural signals has been analyzed as a unidimensional approach (single ligand-receptor effect). However, the in vivo sperm are exposed to multidimensional signaling context, for example, the GABAergic, monoaminergic, purinergic, cholinergic, and melatoninergic, to name a few. The aim of this review is to present an overview of sperm functionality associated with "neuronal signaling" and possible cellular and molecular mechanisms involved in their regulation.
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Affiliation(s)
- Alfredo Ramírez-Reveco
- Instituto de Ciencia Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia, Chile
| | - Franz Villarroel-Espíndola
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.,Department of Pathology and Pediatric Pathology, Yale University, New Haven, Connecticut, USA
| | - Joan E Rodríguez-Gil
- Unitat de Reproducció Animal, Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
| | - Ilona I Concha
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
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12
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Rocha AKADA, de Lima E, Amaral F, Peres R, Cipolla-Neto J, Amado D. Altered MT1 and MT2 melatonin receptors expression in the hippocampus of pilocarpine-induced epileptic rats. Epilepsy Behav 2017; 71:23-34. [PMID: 28460319 DOI: 10.1016/j.yebeh.2017.01.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 01/20/2017] [Accepted: 01/20/2017] [Indexed: 12/11/2022]
Abstract
Clinical and experimental findings show that melatonin may be used as an adjuvant to the treatment of epilepsy-related complications by alleviates sleep disturbances, circadian alterations and attenuates seizures alone or in combination with AEDs. In addition, it has been observed that there is a circadian component on seizures, which cause changes in circadian system and in melatonin production. Nevertheless, the dynamic changes of the melatoninergic system, especially with regard to its membrane receptors (MT1 and MT2) in the natural course of TLE remain largely unknown. The aim of this study was to evaluate the 24-hour profile of MT1 and MT2 mRNA and protein expression in the hippocampus of rats submitted to the pilocarpine-induced epilepsy model analyzing the influence of the circadian rhythm in the expression pattern during the acute, silent, and chronic phases. Melatonin receptor MT1 and MT2 mRNA expression levels were increased in the hippocampus of rats few hours after SE, with MT1 returning to normal levels and MT2 reducing during the silent phase. During the chronic phase, mRNA expression levels of both receptors return to levels close to control, however, presenting a different daily profile, showing that there is a circadian change during the chronic phase. Also, during the acute and silent phase it was possible to verify MT1 label only in CA2 hippocampal region with an increased expression only in the dark period of the acute phase. The MT2 receptor was present in all hippocampal regions, however, it was reduced in the acute phase and it was found in astrocytes. In chronic animals, there is a reduction in the presence of both receptors especially in regions where there is a typical damage derived from epilepsy. Therefore, we conclude that SE induced by pilocarpine is able to change melatonin receptor MT1 and MT2 protein and mRNA expression levels in the hippocampus of rats few hours after SE as well as in silent and chronic phases.
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Affiliation(s)
| | - Eliangela de Lima
- Department of Neurology and Neurosurgery, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil; Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil; Department of Physiology, Universidade Federal de Mato Grosso (UFMT), Cuiabá, Brazil
| | - Fernanda Amaral
- Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil; Departament of Physiology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil
| | - Rafael Peres
- Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil
| | - José Cipolla-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Science, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Débora Amado
- Department of Neurology and Neurosurgery, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil
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13
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Popovska-Gorevski M, Dubocovich ML, Rajnarayanan RV. Carbamate Insecticides Target Human Melatonin Receptors. Chem Res Toxicol 2017; 30:574-582. [PMID: 28027439 DOI: 10.1021/acs.chemrestox.6b00301] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Carbaryl (1-naphthyl methylcarbamate) and carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) are among the most toxic insecticides, implicated in a variety of diseases including diabetes and cancer among others. Using an integrated pharmacoinformatics based screening approach, we have identified these insecticides to be structural mimics of the neurohormone melatonin and were able to bind to the putative melatonin binding sites in MT1 and MT2 melatonin receptors in silico. Carbaryl and carbofuran then were tested for competition with 2-[125I]-iodomelatonin (300 pM) binding to hMT1 or hMT2 receptors stably expressed in CHO cells. Carbaryl and carbofuran showed higher affinity for competition with 2-[125I]-iodomelatonin binding to the hMT2 compared to the hMT1 melatonin receptor (33 and 35-fold difference, respectively) as predicted by the molecular modeling. In the presence of GTP (100 μM), which decouples the G-protein linked receptors to modulate signaling, the apparent efficacy of carbaryl and carbofuran for 2-[125I]-iodomelatonin binding for the hMT1 melatonin receptor was not affected but significantly decreased for the hMT2 melatonin receptor compatible with receptor antagonist/inverse agonist and agonist efficacy, respectively. Altogether, our data points to a potentially new mechanism through which carbamate insecticides carbaryl and carbofuran could impact human health by altering the homeostatic balance of key regulatory processes by directly binding to melatonin receptors.
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Affiliation(s)
- Marina Popovska-Gorevski
- Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo , Buffalo, New York 14221, United States
| | - Margarita L Dubocovich
- Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo , Buffalo, New York 14221, United States
| | - Rajendram V Rajnarayanan
- Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo , Buffalo, New York 14221, United States
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14
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Gonzalez-Arto M, Luna C, Pérez-Pé R, Muiño-Blanco T, Cebrián-Pérez JA, Casao A. New evidence of melatonin receptor contribution to ram sperm functionality. Reprod Fertil Dev 2016; 28:924-935. [DOI: 10.1071/rd14302] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 10/30/2014] [Indexed: 11/23/2022] Open
Abstract
The present study analysed the involvement of melatonin, acting via its receptors (MT1 and MT2), in ram sperm functionality. Indirect immunofluorescence assays revealed no changes in the distribution or intensity of MT1 receptors, whereas different subpopulations were established for MT2 receptors in control, in vitro capacitated and acrosome-reacted ram spermatozoa. Chlortetracycline staining revealed the following correlations between the pattern of staining for MT2 receptors in: (1) non-capacitated (NC) sperm rate and the proportion of spermatozoa with equal immunostaining intensity in the acrosome and post-acrosome (r = 0.59, P < 0.001); (2) in capacitated (C) sperm rate and the proportion of spermatozoa with stronger reactivity in the acrosome (r = 0.60, P < 0.001); and (3) in acrosome-reacted (AR) sperm rate and the proportion of spermatozoa with more intense staining on the post-acrosome (r = 0.67, P < 0.001). Incubation of swim-up-selected samples with either 1 μM melatonin or MT1 and MT2 receptor agonists (2-phenylmelatonin 1 µM and 8-Methoxy-2-propionamidotetralin (8M-PDOT) 1 µM and 10 nM) at 39°C and 5% CO2 for 3 h resulted in a higher proportion of the NC pattern compared with the control group (P < 0.05), whereas treatment with MT1 and MT2 receptor antagonists (luzindole 1 µM and 4-phenyl-2-propionamidotetralin (4P-PDOT) 1 µM and 10 nM) decreased the proportion of spermatozoa exhibiting the NC pattern (P < 0.001) concomitant with an increase in those exhibiting the C pattern (P < 0.01). In conclusion, melatonin exerts a modulating effect on ram sperm functionality, primarily via activation of the MT2 receptor.
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15
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Cebrián-Pérez JA, Casao A, González-Arto M, dos Santos Hamilton TR, Pérez-Pé R, Muiño-Blanco T. Melatonin in sperm biology: breaking paradigms. Reprod Domest Anim 2015; 49 Suppl 4:11-21. [PMID: 25277428 DOI: 10.1111/rda.12378] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 06/19/2014] [Indexed: 12/15/2022]
Abstract
Melatonin is a ubiquitous molecule, present in a wide range of organisms, and involved in multiple functions. Melatonin relays the information about the photoperiod to the tissues that express melatonin-binding sites in both central and peripheral nervous systems. This hormone has a complex mechanism of action. It can cross the cell plasma membrane and exert its actions in all cells of the body. Certain melatonin actions are mediated by receptors that belong to the superfamily of G-protein-coupled receptors (GPCRs), the MT1 and MT2 membrane. Melatonin can also bind to calmodulin as well as to nuclear receptors of the retinoic acid receptor family, RORα1, RORα2 and RZRβ. The purpose of this review is to report on recent developments in the physiological role of melatonin and its receptors. Specific issues concerning the biological function of melatonin in mammalian seasonal reproduction and spermatozoa are considered. The significance of the continuous presence of melatonin in seminal plasma with a fairly constant concentration is also discussed.
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Affiliation(s)
- J A Cebrián-Pérez
- Departamento de Bioquímica y Biología Molecular y Celular, Instituto Universitario de Investigación en Ciencias Ambientales de Aragón (IUCA), Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain
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16
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Peschke E, Bähr I, Mühlbauer E. Experimental and clinical aspects of melatonin and clock genes in diabetes. J Pineal Res 2015; 59:1-23. [PMID: 25904189 DOI: 10.1111/jpi.12240] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/20/2015] [Indexed: 12/15/2022]
Abstract
The pineal hormone melatonin influences insulin secretion, as well as glucagon and somatostatin secretion, both in vivo and in vitro. These effects are mediated by two specific, high-affinity, seven transmembrane, pertussis toxin-sensitive, Gi-protein-coupled melatonin receptors, MT1 and MT2. Both isoforms are expressed in the β-cells, α-cells as well as δ-cells of the pancreatic islets of Langerhans and are involved in the modulation of insulin secretion, leading to inhibition of the adenylate cyclase-dependent cyclic adenosine monophosphate as well as cyclic guanosine monophosphate formation in pancreatic β-cells by inhibiting the soluble guanylate cyclase, probably via MT2 receptors. In this way, melatonin also likely inhibits insulin secretion, whereas using the inositol triphosphate pathway after previous blocking of Gi-proteins by pertussis toxin, melatonin increases insulin secretion. Desynchrony of receptor signaling may lead to the development of type 2 diabetes. This notion has recently been supported by genomewide association studies pinpointing variances of the MT2 receptor as a risk factor for this rapidly spreading metabolic disturbance. As melatonin is secreted in a clearly diurnal fashion, it is safe to assume that it also has a diurnal impact on the blood-glucose-regulating function of the islet. Observations of the circadian expression of clock genes (Clock, Bmal1, Per1,2,3, and Cry1,2) in pancreatic islets, as well as in INS1 rat insulinoma cells, may indicate that circadian rhythms are generated in the β-cells themselves. The circadian secretion of insulin from pancreatic islets is clock-driven. Disruption of circadian rhythms and clock function leads to metabolic disturbances, for example, type 2 diabetes. The study of melatonin-insulin interactions in diabetic rat models has revealed an inverse relationship between these two hormones. Both type 2 diabetic rats and patients exhibit decreased melatonin levels and slightly increased insulin levels, whereas type 1 diabetic rats show extremely reduced levels or the absence of insulin, but statistically significant increases in melatonin levels. Briefly, an increase in melatonin levels leads to a decrease in stimulated insulin secretion and vice versa. Melatonin levels in blood plasma, as well as the activity of the key enzyme of melatonin synthesis, AA-NAT (arylalkylamine-N-acetyltransferase) in pineal, are lower in type 2 diabetic rats compared to controls. In contrast, melatonin and pineal AA-NAT mRNA are increased and insulin receptor mRNA is decreased in type 1 diabetic rats, which also indicates a close relationship between insulin and melatonin. As an explanation, it was hypothesized that catecholamines, which reduce insulin levels and stimulate melatonin synthesis, control insulin-melatonin interactions. This conviction stems from the observation that catecholamines are increased in type 1 but are diminished in type 2 diabetes. In this context, another important line of inquiry involves the fact that melatonin protects β-cells against functional overcharge and, consequently, hinders the development of type 2 diabetes.
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Affiliation(s)
| | - Ina Bähr
- Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
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17
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Effect of Melatonin on the Extracellular-Regulated Kinase Signal Pathway Activation and Human Osteoblastic Cell Line hFOB 1.19 Proliferation. Int J Mol Sci 2015; 16:10337-53. [PMID: 25961946 PMCID: PMC4463649 DOI: 10.3390/ijms160510337] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 04/21/2015] [Accepted: 04/27/2015] [Indexed: 02/06/2023] Open
Abstract
It has been shown that melatonin may affect bone metabolism. However, it is controversial whether melatonin could promote osteoblast proliferation, and the precise molecular mechanism of melatonin on osteoblast proliferation is still obscure. In this study, the results of the CCK-8 assay showed that melatonin significantly promoted human osteoblastic cell line hFOB 1.19 cell proliferation at 1, 2.5, 5, 10, 25, 50 and 100 µM concentrations for 24 h, but there were no significant differences among the groups. Western blot demonstrated that 10 µM melatonin significantly promoted ERK1/2 phosphorylation. Furthermore, we also detected the phosphorylation of c-Raf, MEK1/2, p90RSK and MSK1, and all of them increased with 10 µM melatonin. U0126 (a selective inhibitor of MEK that disrupts downstream activation of ERK1/2) downregulated the phosphorylation of ERK1/2, p90RSK and MSK1. U0126 also attenuated the proliferation of osteoblasts stimulated by melatonin. In conclusion, this study for the first time indicates that melatonin (10 nM–100 µM) promotes the proliferation of a human osteoblastic cell line hFOB 1.19 through activation of c-Raf, MEK1/2, ERK1/2, p90RSK and MSK1.
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In vitro comparison of duration of action of melatonin agonists on melatonin MT1 receptor: possible link between duration of action and dissociation rate from receptor. Eur J Pharmacol 2015; 757:42-52. [PMID: 25797281 DOI: 10.1016/j.ejphar.2015.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 02/03/2015] [Accepted: 03/01/2015] [Indexed: 12/15/2022]
Abstract
Melatonin MT1 and MT2 receptors are Gi protein-coupled receptors and promising therapeutic targets for a number of diseases. A proportion of G protein-coupled receptor agonists and antagonists have been classified according to their duration of action, which influences their pharmacological efficacy. However, the duration of action of melatonin agonists remains unclear. In this study, we investigated the duration of action of melatonin agonists (melatonin, 2-iodomelatonin, ramelteon, and the ramelteon metabolite M-II) at the melatonin MT1 receptor, which is more resistant to agonist-induced desensitization than the melatonin MT2 receptor. In Chinese hamster ovary cells stably expressing the human melatonin MT1 receptor, significant differences in the duration of action were observed after 2-h pretreatment with agonists followed by washout. In contrast to melatonin and M-II, the agonist activities of ramelteon and 2-iodomelatonin were persistent (i.e. inhibition of forskolin-stimulated cAMP formation and increase in ERK 1/2 phosphorylation) even after repeated washouts. Similar activities were observed for INS-1 cells endogenously expressing the rat MT1 receptor. Further, we examined potential factors linked to the duration of action. Residual activities of melatonin agonists after washout strongly correlated with their dissociation rates from the human melatonin MT1 receptor, but not their lipophilicity or extent of desensitization. These data suggest that the in vitro duration of action significantly differs between melatonin agonists and might dictate dissociation kinetics. Characterization of these in vitro properties may facilitate further in vivo study of the duration of action.
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19
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Lipsky RH, Lin M. Genetic predictors of outcome following traumatic brain injury. HANDBOOK OF CLINICAL NEUROLOGY 2015; 127:23-41. [PMID: 25702208 DOI: 10.1016/b978-0-444-52892-6.00003-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The nature of traumatic brain injury (TBI) has acute and chronic outcomes for those who survive. Over time, the chronic process of injury impacts multiple organ systems that may lead to disease. We discuss possible mechanisms and methodological issues in the context of candidate gene association studies using TBI patient populations. Because study population sizes have been generally limited, we discussed results on genes that have been the focus of independent studies. We also present a justification for testing more speculative candidate genes in recovery from TBI, such as those involved in circadian rhythm, to outline the importance of prioritizing functional variants in genes that may modulate recovery or provide neuroprotection from TBI. Finally, we provide a perspective on how future research will integrate population level genetic findings with the biological basis of disease in order to create a resource of predictive outcome measures for individual patients.
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Affiliation(s)
- Robert H Lipsky
- Department of Neurosciences, Inova Health System, Falls Church, VA, USA.
| | - Mingkuan Lin
- Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, VA, USA
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20
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Nycthemeral variation in melatonin receptor expression in the lymphoid organs of a tropical seasonal breeder Funambulus pennanti. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2014; 200:1045-55. [DOI: 10.1007/s00359-014-0959-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Revised: 10/24/2014] [Accepted: 10/25/2014] [Indexed: 12/15/2022]
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21
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Laredo SA, Villalon Landeros R, Trainor BC. Rapid effects of estrogens on behavior: environmental modulation and molecular mechanisms. Front Neuroendocrinol 2014; 35:447-58. [PMID: 24685383 PMCID: PMC4175137 DOI: 10.1016/j.yfrne.2014.03.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 03/11/2014] [Accepted: 03/19/2014] [Indexed: 12/24/2022]
Abstract
Estradiol can modulate neural activity and behavior via both genomic and nongenomic mechanisms. Environmental cues have a major impact on the relative importance of these signaling pathways with significant consequences for behavior. First we consider how photoperiod modulates nongenomic estrogen signaling on behavior. Intriguingly, short days permit rapid effects of estrogens on aggression in both rodents and song sparrows. This highlights the importance of considering photoperiod as a variable in laboratory research. Next we review evidence for rapid effects of estradiol on ecologically-relevant behaviors including aggression, copulation, communication, and learning. We also address the impact of endocrine disruptors on estrogen signaling, such as those found in corncob bedding used in rodent research. Finally, we examine the biochemical mechanisms that may mediate rapid estrogen action on behavior in males and females. A common theme across these topics is that the effects of estrogens on social behaviors vary across different environmental conditions.
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Affiliation(s)
- Sarah A Laredo
- Animal Behavior Graduate Group, University of California, Davis, CA 95616, United States; Center for Neuroscience, University of California, Davis, CA 95616, United States; Department of Psychology, University of California, Davis, CA 95616, United States
| | - Rosalina Villalon Landeros
- Perinatal Research Laboratories, Department of Obstetrics and Gynecology, University of Wisconsin, Madison, WI 53715, United States
| | - Brian C Trainor
- Animal Behavior Graduate Group, University of California, Davis, CA 95616, United States; Center for Neuroscience, University of California, Davis, CA 95616, United States; Department of Psychology, University of California, Davis, CA 95616, United States.
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22
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Nishiyama K, Hirai K. The melatonin agonist ramelteon induces duration-dependent clock gene expression through cAMP signaling in pancreatic INS-1 β-cells. PLoS One 2014; 9:e102073. [PMID: 25013953 PMCID: PMC4094524 DOI: 10.1371/journal.pone.0102073] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 06/13/2014] [Indexed: 02/07/2023] Open
Abstract
Prolonged exposure to melatonin improves glycemic control in animals. Although glucose metabolism is controlled by circadian clock genes, little is known about the role of melatonin signaling and its duration in the regulation of clock gene expression in pancreatic β-cells. Activation of MT1 and MT2 melatonin receptors inhibits cAMP signaling, which mediates clock gene expression. Therefore, this study investigated exposure duration-dependent alterations in cAMP element-binding protein (CREB) phosphorylation and clock gene expression that occur during and after exposure to ramelteon, a selective melatonin agonist used to treat insomnia. In rat INS-1 cells, a pancreatic β-cell line endogenously expressing melatonin receptors, ramelteon persistently decreased CREB phosphorylation during the treatment period (2-14 h), whereas the subsequent washout induced an enhancement of forskolin-stimulated CREB phosphorylation in a duration- and concentration-dependent manner. This augmentation was blocked by forskolin or the melatonin receptor antagonist luzindole. Similarly, gene expression analyses of 7 clock genes revealed the duration dependency of the effects of ramelteon on Rev-erbα and Bmal1 expression through melatonin receptor-mediated cAMP signaling; longer exposure times (14 h) resulted in greater increases in the expression and signaling of Rev-erbα, which is related to β-cell functions. Interestingly, this led to amplified oscillatory Rev-erbα and Bmal1 expression after agonist washout and forskolin stimulation. These results provide new insights into the duration-dependent effects of ramelteon on clock gene expression in INS-1 cells and may improve the understanding of its effect in vivo. The applicability of these results to pancreatic islets awaits further investigation.
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Affiliation(s)
- Keiji Nishiyama
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Ltd., Fujisawa, Kanagawa, Japan
| | - Keisuke Hirai
- CNS Drug Discovery Unit, Pharmaceutical Research Division, Takeda Pharmaceutical Company Ltd., Fujisawa, Kanagawa, Japan
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23
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Chen L, He X, Zhang Y, Chen X, Lai X, Shao J, Shi Y, Zhou N. Melatonin receptor type 1 signals to extracellular signal-regulated kinase 1 and 2 via Gi and Gs dually coupled pathways in HEK-293 cells. Biochemistry 2014; 53:2827-39. [PMID: 24724723 DOI: 10.1021/bi500092e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The pineal gland hormone melatonin exerts its regulatory roles in a variety of physiological and pathological responses through two G protein-coupled receptors, melatonin receptor type 1 (MT1) and melatonin receptor type 2 (MT2), which have been recognized as promising targets in the treatment of a number of human diseases and disorders. The MT1 receptor was identified nearly 20 years ago; however, the molecular mechanisms by which MT1-mediated signaling affects physiology remain to be further elucidated. In this study, using HEK293 cells stably expressing the human MT1 receptor, melatonin induced a concentration-dependent activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2). The melatonin-mediated phosphorylation of ERK1/2 at later time points (≥5 min) was strongly suppressed by pretreatment with pertussis toxin, but only a slight, if any, inhibition of ERK1/2 activation at early time points (≤2 min) was detected. Further experiments demonstrated that the Gβγ subunit, phosphoinositide 3-kinase, and calcium-insensitive protein kinase C were involved in the MT1-mediated activation of ERK1/2 at later time points (≥5 min). Moreover, results derived from cAMP assays combined with a MT1 mutant indicated that the human MT1 receptor could also couple to Gs protein, stimulating intracellular cAMP formation, and that the MT1-induced activation of ERK1/2 at early time points (≤2 min) was mediated by the Gs/cAMP/PKA cascade. Our findings may provide new insights into the pharmacological effects and physiological functions modulated by the MT1-mediated activation of ERK1/2.
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Affiliation(s)
- Linjie Chen
- Institute of Biochemistry, College of Life Sciences, Zhejiang University , Hangzhou, Zhejiang 310058, China
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24
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Mao L, Yuan L, Xiang S, Zeringue SB, Dauchy RT, Blask DE, Hauch A, Hill SM. Molecular deficiency (ies) in MT₁ melatonin signaling pathway underlies the melatonin-unresponsive phenotype in MDA-MB-231 human breast cancer cells. J Pineal Res 2014; 56:246-53. [PMID: 24372669 PMCID: PMC4868402 DOI: 10.1111/jpi.12117] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2013] [Accepted: 12/20/2013] [Indexed: 12/15/2022]
Abstract
Melatonin has been shown repeatedly to inhibit the growth of human breast tumor cells in vitro and in vivo. Its antiproliferative effects have been well studied in MCF-7 human breast cancer cells and several other estrogen receptor α (ERα)-positive human breast cancer cell lines. However, the MDA-MB-231 breast cancer cell line, an ERα-negative cell line widely used in breast cancer research, has been shown to be unresponsive to melatonin's growth-suppressive effect in vitro. Here, we examined the effect of melatonin on the cell proliferation of several ERα-negative breast cancer cell lines including MDA-MB-231, BT-20, and SK-BR-3 cells. Although the MT1 G-protein-coupled receptor is expressed in all three cell lines, melatonin significantly suppressed the proliferation of SK-BR-3 cells without having any significant effect on the growth of MDA-MB-231 and BT-20 cells. We confirmed that the MT1-associated Gα proteins are expressed in MDA-MB-231 cells. Further studies demonstrated that the melatonin unresponsiveness in MDA-MB-231 cells may be caused by aberrant signaling downstream of the Gαi proteins, resulting in differential regulation of ERK1/2 activity.
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Affiliation(s)
- Lulu Mao
- Department of Structural and Cellular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, New Orleans, LA, USA
| | - Lin Yuan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, New Orleans, LA, USA
| | - Shulin Xiang
- Department of Structural and Cellular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, New Orleans, LA, USA
| | - Samantha B. Zeringue
- Department of Surgery, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
| | - Robert T. Dauchy
- Department of Structural and Cellular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Laboratory of Chrono-Neuroendocrine Oncology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, New Orleans, LA, USA
| | - David E. Blask
- Department of Structural and Cellular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Laboratory of Chrono-Neuroendocrine Oncology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, New Orleans, LA, USA
| | - Adam Hauch
- Department of Surgery, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
| | - Steven M. Hill
- Department of Structural and Cellular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, New Orleans, LA, USA
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25
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Laredo SA, Orr VN, McMackin MZ, Trainor BC. The effects of exogenous melatonin and melatonin receptor blockade on aggression and estrogen-dependent gene expression in male California mice (Peromyscus californicus). Physiol Behav 2014; 128:86-91. [PMID: 24518867 DOI: 10.1016/j.physbeh.2014.01.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 01/07/2014] [Accepted: 01/23/2014] [Indexed: 12/27/2022]
Abstract
Photoperiodic regulation of aggression has been well established in several vertebrate species, with rodents demonstrating increased aggression in short day photoperiods as compared to long day photoperiods. Previous work suggests that estrogens regulate aggression via rapid nongenomic pathways in short days and act more slowly in long days, most likely via genomic pathways. The current study therefore examines the role of melatonin in mediating aggression and estrogen-dependent gene transcription. In Experiment 1, male California mice were housed under long day photoperiods and were treated with either 0.3 μg/g of melatonin, 40 mg/kg of the melatonin receptor antagonist luzindole, or vehicle for 10 days. We found that melatonin administration significantly increased aggression as compared to mice receiving vehicle, but this phenotype was not completely ameliorated by luzindole. In Experiment 2, male California mice were injected with either 1mg/kg of the aromatase inhibitor letrozole or vehicle, and oxytocin receptor (OTR), estrogen receptor alpha (ERα), and c-fos gene expression was examined in the bed nucleus of the stria terminalis (BNST) and medial preoptic area (MPOA). In the BNST, but not MPOA, OTR mRNA was significantly downregulated following letrozole administration, indicating that OTR is an estrogen-dependent gene in the BNST. In contrast, ERα was not estrogen dependent in either brain region. In the MPOA, OTR mRNA was inhibited by melatonin, and luzindole suppressed this effect. C-fos and ERα did not differ between treatments in any brain region examined. These results suggest that it is unlikely that melatonin facilitates aggression via broad spectrum regulation of estrogen-dependent gene expression. Instead, melatonin may act via regulation of other transcription factors such as extracellular signal regulated kinase.
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Affiliation(s)
- Sarah A Laredo
- Department of Psychology and Center for Neuroscience, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA; Animal Behavior Graduate Group, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA.
| | - Veronica N Orr
- Department of Psychology and Center for Neuroscience, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Marissa Z McMackin
- Department of Psychology and Center for Neuroscience, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA; Molecular, Cellular and Integrative Physiology Graduate Group, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Brian C Trainor
- Department of Psychology and Center for Neuroscience, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA; Animal Behavior Graduate Group, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA; Molecular, Cellular and Integrative Physiology Graduate Group, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA
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26
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Melatonin and pancreatic islets: interrelationships between melatonin, insulin and glucagon. Int J Mol Sci 2013; 14:6981-7015. [PMID: 23535335 PMCID: PMC3645673 DOI: 10.3390/ijms14046981] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 03/07/2013] [Accepted: 03/11/2013] [Indexed: 12/15/2022] Open
Abstract
The pineal hormone melatonin exerts its influence in the periphery through activation of two specific trans-membrane receptors: MT1 and MT2. Both isoforms are expressed in the islet of Langerhans and are involved in the modulation of insulin secretion from β-cells and in glucagon secretion from α-cells. De-synchrony of receptor signaling may lead to the development of type 2 diabetes. This notion has recently been supported by genome-wide association studies identifying particularly the MT2 as a risk factor for this rapidly spreading metabolic disturbance. Since melatonin is secreted in a clearly diurnal fashion, it is safe to assume that it also has a diurnal impact on the blood-glucose-regulating function of the islet. This factor has hitherto been underestimated; the disruption of diurnal signaling within the islet may be one of the most important mechanisms leading to metabolic disturbances. The study of melatonin–insulin interactions in diabetic rat models has revealed an inverse relationship: an increase in melatonin levels leads to a down-regulation of insulin secretion and vice versa. Elucidation of the possible inverse interrelationship in man may open new avenues in the therapy of diabetes.
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27
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Huang H, Wang Z, Weng SJ, Sun XH, Yang XL. Neuromodulatory role of melatonin in retinal information processing. Prog Retin Eye Res 2013; 32:64-87. [PMID: 22986412 DOI: 10.1016/j.preteyeres.2012.07.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/24/2012] [Accepted: 07/25/2012] [Indexed: 12/15/2022]
Affiliation(s)
- Hai Huang
- Institute of Neurobiology, Institutes of Brain Science, Fudan University, Shanghai, PR China
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28
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Mao L, Cheng Q, Guardiola-Lemaître B, Schuster-Klein C, Dong C, Lai L, Hill SM. In vitro and in vivo antitumor activity of melatonin receptor agonists. J Pineal Res 2010; 49:210-21. [PMID: 20609073 DOI: 10.1111/j.1600-079x.2010.00781.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Melatonin has been shown to inhibit the proliferation of estrogen receptor α (ERα)-positive human breast cancer cells in vitro and suppress the growth of carcinogen-induced mammary tumors in rats. Melatonin's antiproliferative effect is mediated, at least in part, through the MT1 melatonin receptor and mechanisms involving modulation of the estrogen-signaling pathway. To develop melatonin analogs with greater therapeutic effects, we have examined the in vitro and in vivo antimitotic activity of two MT1/MT2 melatonin receptor agonists, S23219-1 and S23478-1. In our studies, both agonists are quite effective at suppressing the growth of MCF-7 human breast cancer cells. At a concentration of 10⁻⁶ m, S23219-1 and S23478-1 inhibited the growth of MCF-7 cells by 60% and 73%, respectively. However, S23478-1 is more effective than melatonin and S23219-1 at repressing the expression and transactivation of the ERα, and modulating the expression of pancreatic spasmolytic polypeptide (pS2), an estrogen-regulated gene. The melatonin agonist S23478-1 exhibited enhanced antitumor potency in the subsequent studies in our animal model. At a dosage of 25 mg/kg/day, S23478-1 is more efficacious than melatonin at inducing regression of the established N-nitroso-N-methyl-urea-induced rat mammary tumors. This dose of S23478-1 (25 mg/kg/day) generated a significant (P < 0.05) overall regression response of 52%. Furthermore, at this dosage, S23478-1 is more effective than melatonin at suppressing the estrogen-signaling pathway and promoting tumor cell apoptosis, significantly increasing the expression of the pro-apoptotic protein Bax, while decreasing the expression of ERα and the anti-apoptotic protein Bcl-2.
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Affiliation(s)
- Lulu Mao
- Department of Structural & Cellular Biology, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA
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29
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Dubocovich ML, Delagrange P, Krause DN, Sugden D, Cardinali DP, Olcese J. International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, classification, and pharmacology of G protein-coupled melatonin receptors. Pharmacol Rev 2010; 62:343-80. [PMID: 20605968 PMCID: PMC2964901 DOI: 10.1124/pr.110.002832] [Citation(s) in RCA: 400] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The hormone melatonin (5-methoxy-N-acetyltryptamine) is synthesized primarily in the pineal gland and retina, and in several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Melatonin receptors receive and translate melatonin's message to influence daily and seasonal rhythms of physiology and behavior. The melatonin message is translated through activation of two G protein-coupled receptors, MT(1) and MT(2), that are potential therapeutic targets in disorders ranging from insomnia and circadian sleep disorders to depression, cardiovascular diseases, and cancer. This review summarizes the steps taken since melatonin's discovery by Aaron Lerner in 1958 to functionally characterize, clone, and localize receptors in mammalian tissues. The pharmacological and molecular properties of the receptors are described as well as current efforts to discover and develop ligands for treatment of a number of illnesses, including sleep disorders, depression, and cancer.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo State University of New York, 3435 Main Street, Buffalo, NY 14214, USA.
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30
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Lai L, Yuan L, Chen Q, Dong C, Mao L, Rowan B, Frasch T, Hill SM. The Galphai and Galphaq proteins mediate the effects of melatonin on steroid/thyroid hormone receptor transcriptional activity and breast cancer cell proliferation. J Pineal Res 2008; 45:476-88. [PMID: 18705646 PMCID: PMC4879591 DOI: 10.1111/j.1600-079x.2008.00620.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Melatonin, via its MT1 receptor, but not the MT2 receptor, can modulate the transcriptional activity of various nuclear receptors - estrogen receptor alpha (ERalpha) and retinoic acid receptor alpha (RARalpha), but not ERbeta- in MCF-7, T47D, and ZR-75-1 human breast cancer cell lines. The anti-proliferative and nuclear receptor modulatory actions of melatonin are mediated via the MT1 G protein-coupled receptor expressed in human breast cancer cells. However, the specific G proteins and associated pathways involved in the nuclear receptor transcriptional regulation by melatonin are not yet clear. Upon activation, the MT1 receptor specifically couples to the G(alphai2), G(alphai3), G(alphaq), and G(alphall) proteins, and via activation of G(alphai2) proteins, melatonin suppresses forskolin-induced 3',5'-cyclic adenosine monophosphate production, while melatonin activation of G(alphaq), is able to inhibit phospholipid hydrolysis and ATP's induction of inositol triphosphate production in MCF-7 breast cancer cells. Employing dominant-negative and dominant-positive) forms of these G proteins, we demonstrate that G(alphai2) proteins mediate the suppression of estrogen-induced ERalpha transcriptional activity by melatonin, while the G(q) protein mediates the enhancement of retinoid-induced RARalpha transcriptional activity by melatonin. However, the growth-inhibitory actions of melatonin are mediated via both G(alphai2) and G(alphaq) proteins.
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MESH Headings
- Blotting, Western
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Cell Line, Tumor
- Cell Proliferation
- Colforsin/pharmacology
- Cyclic AMP/analysis
- Cyclic GMP/analysis
- Estrogens/physiology
- Female
- GTP-Binding Protein alpha Subunits, Gi-Go/genetics
- GTP-Binding Protein alpha Subunits, Gi-Go/physiology
- Gene Expression Regulation
- Humans
- Immunoprecipitation
- Luciferases
- Melatonin/physiology
- Phosphorus Radioisotopes
- Radioimmunoassay
- Receptor, Melatonin, MT1/physiology
- Receptors, Estrogen/genetics
- Receptors, Estrogen/metabolism
- Receptors, Retinoic Acid/genetics
- Receptors, Retinoic Acid/metabolism
- Receptors, Thyroid Hormone/genetics
- Retinoic Acid Receptor alpha
- Transcription, Genetic
- Transfection
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Affiliation(s)
- Ling Lai
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Lin Yuan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Qi Chen
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Chunmin Dong
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Lulu Mao
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Brian Rowan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
- Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA, USA
| | - Tripp Frasch
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Steven M. Hill
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
- Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA, USA
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31
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Melatonin signaling in mouse cerebellar granule cells with variable native MT1 and MT2 melatonin receptors. Brain Res 2008; 1227:19-25. [PMID: 18621029 DOI: 10.1016/j.brainres.2008.06.082] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 05/28/2008] [Accepted: 06/13/2008] [Indexed: 11/21/2022]
Abstract
Although G protein-coupled MT1 and MT2 melatonin receptors are expressed in neurons of the mammalian brain including in humans, relatively little is known about the influence of native MT1 and MT2 melatonin receptors on neuronal melatonin signaling. Whereas human cerebellar granule cells (CGC) express only MT1 receptors, mouse CGC express both MT1 and MT2. To study the effects of altered neuronal MT1/MT2 receptors, we used CGC cultures prepared from immature cerebella of wild-type mice (MT1/MT2 CGC) and MT1- and MT2-knockout mice (MT2 and MT1 CGC, respectively). Here we report that in MT1/MT2 cultures, physiological (low nanomolar) concentrations of melatonin decrease the activity (phosphorylation) of extracellular-signal-regulated kinase (ERK) whereas a micromolar concentration was ineffective. Both MT1 and MT2 deficiencies transformed the melatonin inhibition of ERK into melatonin-induced ERK activation. In MT1/MT2 CGC, 1 nM melatonin inhibited serine/threonine kinase Akt, whereas in MT1 and MT2 CGC, this concentration was ineffective. Under these conditions, both MT1 and MT2 deficiencies prevented melatonin from inhibiting forskolin-stimulated cAMP levels and cFos immunoreactivity. We demonstrated that selective removal of native neuronal MT1 and MT2 receptors has a profound effect on the intracellular actions of low/physiological concentrations of melatonin. Since the expression of MT1 and MT2 receptors is cell-type-specific and species-dependent, we postulate that the pattern of expression of neuronal melatonin receptor types in different brain areas and cells could determine the capabilities of endogenous melatonin in regulating neuronal functioning.
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32
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Melatonin receptors, heterodimerization, signal transduction and binding sites: what's new? Br J Pharmacol 2008; 154:1182-95. [PMID: 18493248 DOI: 10.1038/bjp.2008.184] [Citation(s) in RCA: 219] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Melatonin is a neurohormone that has been claimed to be involved in a wide range of physiological functions. Nevertheless, for most of its effects, the mechanism of action is not really known. In mammals, two melatonin receptors, MT1 and MT2, have been cloned. They belong to the G-protein-coupled receptor (GPCR) superfamily. They share some specific short amino-acid sequences, which suggest that they represent a specific subfamily. Another receptor from the same subfamily, the melatonin-related receptor has been cloned in different species including humans. This orphan receptor also named GPR50 does not bind melatonin and its endogenous ligand is still unknown. Nevertheless, this receptor has been shown to behave as an antagonist of the MT1 receptor, which opens new pharmacological perspectives for GPR50 despite the lack of endogenous or synthetic ligands. Moreover, MT1 and MT2 interact together through the formation of heterodimers at least in cells transfected with the cDNA of these two receptors. Lastly, signalling complexes associated with MT1 and MT2 receptors are starting to be deciphered. A third melatonin-binding site has been purified and characterized as the enzyme quinone reductase 2 (QR2). Inhibition of QR2 by melatonin may explain melatonin's protective effect that has been reported in different animal models and that is generally associated with its well-documented antioxidant properties.
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33
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Radio NM, Doctor JS, Witt-Enderby PA. Melatonin enhances alkaline phosphatase activity in differentiating human adult mesenchymal stem cells grown in osteogenic medium via MT2 melatonin receptors and the MEK/ERK (1/2) signaling cascade. J Pineal Res 2006; 40:332-42. [PMID: 16635021 DOI: 10.1111/j.1600-079x.2006.00318.x] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The goals of this study were to determine (a) if melatonin enhances human adult mesenchymal stem cell (hAMSC) differentiation into osteoblasts as assessed by measuring alkaline phosphatase (ALP) enzyme activity, and (b) identify potential signal transduction pathways that mediate this process. ALP activity significantly increased in hAMSCs following a 10-day incubation in osteogenic medium, relative to hAMSCs incubated in basal growth medium alone. Melatonin (50 nm), added in combination with the osteogenic medium, significantly increased ALP activity relative to osteogenic medium alone. Co-exposure of hAMSCs to osteogenic medium supplemented with melatonin and either pertussis toxin or the melatonin receptor antagonists, luzindole or 4P-PDOT (MT2 receptor selective), inhibited the melatonin-induced increase in ALP activity, indicating the involvement of melatonin receptors, in particular, MT2 receptors. Assessment of melatonin receptor function following exposure to osteogenic medium containing either vehicle or melatonin produced dichotomous results. That is, if the differentiation of hAMSCs into an osteoblast was induced by osteogenic medium alone, then 2-[125I]-iodomelatonin binding and melatonin receptor function increased. However, examination of melatonin receptor function following chronic melatonin exposure, an exposure that resulted in a 50% enhancement in ALP activity, revealed that these receptors were desensitized. This was reflected by a complete loss in specific 2-[125I]-iodomelatonin binding as well as melatonin efficacy to inhibit forskolin-induced cAMP accumulation. Further characterization of the mechanisms underlying melatonin's effects on these differentiation processes revealed that MEK (1/2) and ERK (1/2), epidermal growth factor receptors, metalloproteinase and clathrin-mediated endocytosis were essential while PKA was not. Our results are consistent with a role for melatonin in osteoblast differentiation. If so, then, the decrease in plasma melatonin levels observed in humans during late adulthood may further enhance susceptibility to osteoporosis.
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Affiliation(s)
- Nicholas M Radio
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA 15282, USA
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34
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Abstract
Melatonin, dubbed the hormone of darkness, is known to regulate a wide variety of physiological processes in mammals. This review describes well-defined functional responses mediated through activation of high-affinity MT1 and MT2 G protein-coupled receptors viewed as potential targets for drug discovery. MT1 melatonin receptors modulate neuronal firing, arterial vasocon-striction, cell proliferation in cancer cells, and reproductive and metabolic functions. Activation of MT2 melatonin receptors phase shift circadian rhythms of neuronal firing in the suprachiasmatic nucleus, inhibit dopamine release in retina, induce vasodilation and inhibition of leukocyte rolling in arterial beds, and enhance immune responses. The melatonin-mediated responses elicited by activation of MT1 and MT2 native melatonin receptors are dependent on circadian time, duration and mode of exposure to endogenous or exogenous melatonin, and functional receptor sensitivity. Together, these studies underscore the importance of carefully linking each melatonin receptor type to specific functional responses in target tissues to facilitate the design and development of novel therapeutic agent.
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Affiliation(s)
- Margarita L Dubocovich
- Department of Molecular Pharmacology & Biological Chemistry, Northwestern University Feinberg School of Medicine Center for Drug Discovery and Chemical Biology, Chicago, IL 60611, USA.
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35
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Kayampilly PP, Menon KMJ. Inhibition of extracellular signal-regulated protein kinase-2 phosphorylation by dihydrotestosterone reduces follicle-stimulating hormone-mediated cyclin D2 messenger ribonucleic acid expression in rat granulosa cells. Endocrinology 2004; 145:1786-93. [PMID: 14691013 DOI: 10.1210/en.2003-1029] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Granulosa cell mitogenesis is critical for the development of normal ovarian follicles. FSH and other mitogenic stimuli play a crucial role in this process. We have shown that exposing granulosa cells to 5alpha-dihydrotestosterone (DHT) reduces forskolin-stimulated cyclin D2 mRNA expression, which leads to cell cycle arrest resulting in reduced cell proliferation. The present study investigated the signaling molecules upstream of cyclin D2 in FSH-mediated, cAMP-dependent signaling pathway that may be negatively affected by DHT, leading to inhibition of cell cycle progression. Because ERK is an important molecule in mitogenic signaling, the possible effect of DHT on its phosphorylation was examined. Granulosa cells from 3-d estradiol-primed immature rats were treated with DHT (90 ng/ml) for 24 h and subsequently stimulated with forskolin. DHT treatment reduced forskolin stimulation of ERK phosphorylation. Although DHT exposure did not affect cellular cAMP production in response to forskolin, treating the cells with DHT for 24 h significantly reduced protein kinase A activity. DHT also caused a reduction in ERK-2 phosphorylation in response to FSH similar to that seen with forskolin. Furthermore, blocking ERK phosphorylation as well as DHT treatment resulted in a reduction in FSH-stimulated cyclin D2 mRNA expression. From these results, we conclude that DHT treatment reduces the FSH-mediated ERK phosphorylation in granulosa cells, leading to reduced cyclin D2 mRNA expression that culminates in cell cycle arrest.
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Affiliation(s)
- Pradeep P Kayampilly
- Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor 48109, USA
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36
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Steffens F, Zhou XB, Sausbier U, Sailer C, Motejlek K, Ruth P, Olcese J, Korth M, Wieland T. Melatonin receptor signaling in pregnant and nonpregnant rat uterine myocytes as probed by large conductance Ca2+-activated K+ channel activity. Mol Endocrinol 2003; 17:2103-15. [PMID: 12869590 DOI: 10.1210/me.2003-0047] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The mRNAs of MT1 and MT2 melatonin receptors are present in cells from nonpregnant (NPM) and pregnant (PM) rat myometrium. To investigate the coupling of melatonin receptors to Gq- and Gi-type of heterotrimeric G proteins, we analyzed the activity of large-conductance Ca2+-activated K+ (BKCa) channels, the expression of which in the uterus is confined to smooth muscle cells. The melatonin receptor agonist 2-iodomelatonin induced a pertussis toxin (PTX)-insensitive increase in channel open probability that was blocked by the nonselective antagonist luzindole. The 2-iodomelatonin effect on channel open probability was suppressed by overexpression of the Gqalpha-inactivating protein RGS16 and the phospholipase C inhibitor U-73122. The activity of BKCa channels is differentially regulated by protein kinase A (PKA) in NPM and PM cells. Thus, the beta-adrenoceptor agonist isoprenaline inhibited the BKCa channel conducted whole-cell outward current (Iout) in NPM cells and enhanced Iout in PM cells. Additional application of 2-iodomelatonin antagonized the isoprenaline effect on Iout in NPM cells but enhanced Iout in PM cells. All 2-iodomelatonin effects on Iout were sensitive to PTX treatment and the PKA inhibitor H-89. We therefore conclude that melatonin activates both the PTX-insensitive Gq/phospholipase C/Ca2+ and the PTX-sensitive Gi/cAMP/PKA signaling pathway in rat myometrium.
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MESH Headings
- Animals
- Calcium/pharmacology
- Cyclic AMP/metabolism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Female
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- Isoproterenol/pharmacology
- Large-Conductance Calcium-Activated Potassium Channels
- Melatonin/analogs & derivatives
- Melatonin/pharmacology
- Membrane Potentials
- Myometrium/cytology
- Myometrium/metabolism
- Pertussis Toxin/pharmacology
- Potassium Channels, Calcium-Activated/physiology
- Pregnancy
- Rats
- Rats, Wistar
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Signal Transduction
- Type C Phospholipases/metabolism
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Affiliation(s)
- Frank Steffens
- Institut für Pharmakologie für Pharmazeuten, Universitätsklinikum Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany
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37
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Abstract
Sensitization of adenylate cyclase is a recently discovered phenomenon. Melatonin can induce a sensitized response of adenylate cyclase in ovine pars tuberalis cells where the receptor for melatonin is endogenously expressed. Although the mechanism is not fully understood, sensitization of adenylate cyclase may be an important part of the mechanism by which melatonin encodes daylength in the pars tuberalis of sheep and other animals. We used this as a hypothesis to search for a natural ligand that would activate adenylate cyclase in ovine pars tuberalis cells. The approach revealed pituitary adenylate cyclase activating polypeptide to be an indirect activator of adenylate cyclase in the ovine pars tuberalis. We discuss this in relation to the mechanism and importance of sensitization to the function to the pars tuberalis.
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Affiliation(s)
- P Barrett
- Molecular Neuroendocrinology Group, Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, Scotland, UK.
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38
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Masana MI, Witt-Enderby PA, Dubocovich ML. Melatonin differentially modulates the expression and function of the hMT1 and hMT2 melatonin receptors upon prolonged withdrawal. Biochem Pharmacol 2003; 65:731-9. [PMID: 12628486 DOI: 10.1016/s0006-2952(02)01627-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin is synthesized and released following a circadian rhythm and reaches its highest blood levels during the night. It relays signals of darkness to target tissues involved in regulating circadian and seasonal rhythms. Here, we report the expression of human melatonin receptors type 1 and 2 (hMT(1) and hMT(2), respectively) in Chinese hamster ovary (CHO) cells following exposure to melatonin treatments mimicking the amplitude (400 pM) and duration (8 hr) of the nightly melatonin peak and upon withdrawal. Exposure of CHO-MT(1) cells to melatonin (400 pM) for 0.5, 1, 2, 4, and 8 hr significantly increased specific 2-[125I]iodomelatonin (500 pM) binding to hMT(1) melatonin receptors upon 16-hr withdrawal. However, the same treatment did not affect the expression of hMT(2) melatonin receptors. The increase in specific 2-[125I]iodomelatonin (500 pM) binding (162+/-29%, N=3, P<0.05) 16 hr after melatonin withdrawal was parallel to increases in hMT(1) melatonin receptor mRNA (231+/-33%, N=4, P<0.05). This effect was due to an increase in the total number of hMT(1) receptors [B(max) 833+/-97 fmol/mg protein (N=3), control; 1449+/-41 fmol/mg protein (N=3), treated], with no change in binding affinity. The melatonin-mediated increase in MT(1) melatonin receptor expression upon withdrawal was not mediated through either a direct effect of the hormone in the promoter's vector or in the rate of mRNA degradation. In conclusion, melatonin differentially regulates the expression of its own receptors, which may have important implications in the transduction of dark signals in vivo.
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Affiliation(s)
- Monica I Masana
- Department of Molecular Pharmacology and Biological Chemistry (S215), Northwestern University Medical School, 303 East Chicago Ave., IL 60611, USA
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39
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MacKenzie RS, Melan MA, Passey DK, Witt-Enderby PA. Dual coupling of MT(1) and MT(2) melatonin receptors to cyclic AMP and phosphoinositide signal transduction cascades and their regulation following melatonin exposure. Biochem Pharmacol 2002; 63:587-95. [PMID: 11992626 DOI: 10.1016/s0006-2952(01)00881-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In this investigation, we wanted to determine whether MT(1) or MT(2) melatonin receptors are capable of coupling to the phosphoinositide (PI) signal transduction cascade. In addition, we wanted to assess the effects of chronic melatonin exposure on MT(1) and MT(2) melatonin receptor-mediated stimulation of PI hydrolysis. We also assessed the effects of chronic melatonin exposure on other parameters of the MT(2) melatonin receptor function including total specific 2-[125I]-iodomelatonin binding, the affinity of melatonin for the receptor, and melatonin (1nM)-mediated inhibition of cyclic 3',5'-adenosine monophosphate (cAMP) accumulation. Investigation of the PI signal transduction cascade activated by either the MT(1) or MT(2) melatonin receptor expressed in Chinese hamster ovary (CHO) cells showed that melatonin (1pM to 1mM) was able to stimulate the formation of PIs to approximately 40-60% over basal [EC(50): MT(1)=29nM (2-300nM) and MT(2)=1.1nM (0.32-3.5nM), N=5]. This response was mediated via receptors based upon the findings that melatonin did not stimulate the formation of PIs in CHO cells devoid of receptor and that antagonism of MT(2) melatonin receptors by 4P-PDOT (AH 024; 4-phenyl-2-propionamidotetralin) attenuated melatonin-mediated stimulation of PI hydrolysis in CHO cells expressing the MT(2) melatonin receptor. The consequence of chronic melatonin exposure on MT(1) and MT(2) receptor function was also examined. Pretreatment of either MT(1)- or MT(2)-CHO cells with melatonin (1 microM for 5hr) resulted in: (a) a complete loss of melatonin-mediated stimulation of PI hydrolysis, and (b) an attenuation of melatonin (1nM)-mediated inhibition of forskolin-induced cAMP accumulation by approximately 20-40%. The desensitization of the PI hydrolysis signal transduction cascades coupled to either MT(1) or MT(2) melatonin receptors following chronic melatonin exposure was not due to depleted phospholipid pools, to elevated basal levels, or to decreases in receptor affinity and density. This dual coupling of melatonin receptors to different signal transduction cascades may contribute to the diversity of melatonin receptor function in vivo.
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Affiliation(s)
- Renee S MacKenzie
- Department of Pharmacology and Toxicology, School of Pharmacy, Duquesne University, Pittsburgh, PA 15282, USA
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Masana MI, Dubocovich ML. Melatonin receptor signaling: finding the path through the dark. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2001; 2001:pe39. [PMID: 11698691 DOI: 10.1126/stke.2001.107.pe39] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin, dubbed "the hormone of darkness," is involved in relaying photoperiodic information to the organism. Not only is melatonin involved in the regulation of circadian rhythms and sleep, but it also has roles in visual, cerebrovascular, reproductive, neuroendocrine, and neuroimmunological functions. Melatonin mediates its effects through G protein-coupled receptors: MT(1), MT(2), and, possibly, MT(3). Pharmacological agents have been instrumental in identifying these receptor types. Masana and Dubocovich discuss how the level of receptor expression may alter their efficacy, so that caution is necessary when extrapolating the pharmacological properties of ligands defined on recombinant systems to the receptors in the organism. With these cautions in mind, they describe the various signaling pathways and physiological roles ascribed to the three melatonin receptor types.
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Affiliation(s)
- M I Masana
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, IL 60611, USA
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Nelson CS, Ikeda M, Gompf HS, Robinson ML, Fuchs NK, Yoshioka T, Neve KA, Allen CN. Regulation of melatonin 1a receptor signaling and trafficking by asparagine-124. Mol Endocrinol 2001; 15:1306-17. [PMID: 11463855 DOI: 10.1210/mend.15.8.0681] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Melatonin is a pineal hormone that regulates seasonal reproduction and has been used to treat circadian rhythm disorders. The melatonin 1a receptor is a seven- transmembrane domain receptor that signals predominately via pertussis toxin-sensitive G-proteins. Point mutations were created at residue N124 in cytoplasmic domain II of the receptor and the mutant receptors were expressed in a neurohormonal cell line. The acidic N124D- and E-substituted receptors had high-affinity (125)I-melatonin binding and a subcellular localization similar to the neutral N124N wild-type receptor. Melatonin efficacy for the inhibition of cAMP by N124D and E mutations was significantly decreased. N124D and E mutations strongly compromised melatonin efficacy and potency for inhibition of K(+)-induced intracellular Ca(++) fluxes and eliminated control of spontaneous calcium fluxes. However, these substitutions did not appear to affect activation of Kir3 potassium channels. The hydrophobic N124L and N124A or basic N124K mutations failed to bind (125)I-melatonin and appeared to aggregate or traffic improperly. N124A and N124K receptors were retained in the Golgi. Therefore, mutants at N124 separated into two sets: the first bound (125)I-melatonin with high affinity and trafficked normally, but with reduced inhibitory coupling to adenylyl cyclase and Ca(++) channels. The second set lacked melatonin binding and exhibited severe trafficking defects. In summary, asparagine-124 controls melatonin receptor function as evidenced by changes in melatonin binding, control of cAMP levels, and regulation of ion channel activity. Asparagine-124 also has a unique structural effect controlling receptor distribution within the cell.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Animals
- Asparagine
- Calcium/metabolism
- Calcium Channels/metabolism
- Cyclic AMP/metabolism
- Electrophysiology
- Fluorescent Antibody Technique
- G Protein-Coupled Inwardly-Rectifying Potassium Channels
- Golgi Apparatus/metabolism
- Iodine Radioisotopes
- Melatonin/metabolism
- Melatonin/pharmacology
- Mice
- Mutagenesis, Site-Directed
- Pituitary Neoplasms
- Potassium/pharmacology
- Potassium Channels/drug effects
- Potassium Channels/physiology
- Potassium Channels, Inwardly Rectifying
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/physiology
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/physiology
- Receptors, Melatonin
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
- Tumor Cells, Cultured
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Affiliation(s)
- C S Nelson
- Center for Research on Occupational and Environmental Toxicology, Oregon Health Sciences University, Portland, Oregon 97201, USA
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Hazlerigg DG, Morgan PJ, Messager S. Decoding photoperiodic time and melatonin in mammals: what can we learn from the pars tuberalis? J Biol Rhythms 2001; 16:326-35. [PMID: 11506378 DOI: 10.1177/074873001129002042] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The cellular and molecular mechanisms through which the melatonin signal is decoded to drive/synchronize photoperiodic responses remain unclear. Much of our current understanding of the processes involved in this readout derives from studies of melatonin action in the pars tuberalis of the anterior pituitary. Here, the authors review current knowledge and highlight critical gaps in our present understanding.
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Affiliation(s)
- D G Hazlerigg
- Aberdeen Centre for Energy Regulation and Obesity, University of Aberdeen, Scotland, UK.
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