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Meléndez-Fernández OH, Liu JA, Nelson RJ. Circadian Rhythms Disrupted by Light at Night and Mistimed Food Intake Alter Hormonal Rhythms and Metabolism. Int J Mol Sci 2023; 24:3392. [PMID: 36834801 PMCID: PMC9963929 DOI: 10.3390/ijms24043392] [Citation(s) in RCA: 29] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 02/04/2023] [Accepted: 02/07/2023] [Indexed: 02/10/2023] Open
Abstract
Availability of artificial light and light-emitting devices have altered human temporal life, allowing 24-hour healthcare, commerce and production, and expanding social life around the clock. However, physiology and behavior that evolved in the context of 24 h solar days are frequently perturbed by exposure to artificial light at night. This is particularly salient in the context of circadian rhythms, the result of endogenous biological clocks with a rhythm of ~24 h. Circadian rhythms govern the temporal features of physiology and behavior, and are set to precisely 24 h primarily by exposure to light during the solar day, though other factors, such as the timing of meals, can also affect circadian rhythms. Circadian rhythms are significantly affected by night shift work because of exposure to nocturnal light, electronic devices, and shifts in the timing of meals. Night shift workers are at increased risk for metabolic disorder, as well as several types of cancer. Others who are exposed to artificial light at night or late mealtimes also show disrupted circadian rhythms and increased metabolic and cardiac disorders. It is imperative to understand how disrupted circadian rhythms alter metabolic function to develop strategies to mitigate their negative effects. In this review, we provide an introduction to circadian rhythms, physiological regulation of homeostasis by the suprachiasmatic nucleus (SCN), and SCN-mediated hormones that display circadian rhythms, including melatonin and glucocorticoids. Next, we discuss circadian-gated physiological processes including sleep and food intake, followed by types of disrupted circadian rhythms and how modern lighting disrupts molecular clock rhythms. Lastly, we identify how disruptions to hormones and metabolism can increase susceptibility to metabolic syndrome and risk for cardiovascular diseases, and discuss various strategies to mitigate the harmful consequences associated with disrupted circadian rhythms on human health.
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Cecon E, Fernandois D, Renault N, Coelho CFF, Wenzel J, Bedart C, Izabelle C, Gallet S, Le Poder S, Klonjkowski B, Schwaninger M, Prevot V, Dam J, Jockers R. Melatonin drugs inhibit SARS-CoV-2 entry into the brain and virus-induced damage of cerebral small vessels. Cell Mol Life Sci 2022; 79:361. [PMID: 35697820 PMCID: PMC9191404 DOI: 10.1007/s00018-022-04390-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/11/2022] [Accepted: 05/20/2022] [Indexed: 02/07/2023]
Abstract
COVID-19 is a complex disease with short- and long-term respiratory, inflammatory and neurological symptoms that are triggered by the infection with SARS-CoV-2. Invasion of the brain by SARS-CoV-2 has been observed in humans and is postulated to be involved in post-COVID state. Brain infection is particularly pronounced in the K18-hACE2 mouse model of COVID-19. Prevention of brain infection in the acute phase of the disease might thus be of therapeutic relevance to prevent long-lasting symptoms of COVID-19. We previously showed that melatonin or two prescribed structural analogs, agomelatine and ramelteon delay the onset of severe clinical symptoms and improve survival of SARS-CoV-2-infected K18-hACE2 mice. Here, we show that treatment of K18-hACE2 mice with melatonin and two melatonin-derived marketed drugs, agomelatine and ramelteon, prevents SARS-CoV-2 entry in the brain, thereby reducing virus-induced damage of small cerebral vessels, immune cell infiltration and brain inflammation. Molecular modeling analyses complemented by experimental studies in cells showed that SARS-CoV-2 entry in endothelial cells is prevented by melatonin binding to an allosteric-binding site on human angiotensin-converting enzyme 2 (ACE2), thus interfering with ACE2 function as an entry receptor for SARS-CoV-2. Our findings open new perspectives for the repurposing of melatonergic drugs and its clinically used analogs in the prevention of brain infection by SARS-CoV-2 and COVID-19-related long-term neurological symptoms.
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Affiliation(s)
- Erika Cecon
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014, Paris, France
| | - Daniela Fernandois
- Univ. Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, UMR-S 1172, FHU 1000 Days for Health, Lille, France
| | - Nicolas Renault
- Univ Lille, INSERM, CHU Lille, U-1286 - INFINTE - Institute for Translational Research in Inflammation, 59000, Lille, France
| | - Caio Fernando Ferreira Coelho
- Univ. Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, UMR-S 1172, FHU 1000 Days for Health, Lille, France
| | - Jan Wenzel
- Institute for Experimental and Clinical Pharmacology and Toxicology, Center for Brain, Behavior and Metabolism (CBBM), University of Lübeck, Lübeck, Germany.,DZHK (German Research Centre for Cardiovascular Research), Hamburg-Lübeck-Kiel, Hamburg, Germany
| | - Corentin Bedart
- Univ Lille, INSERM, CHU Lille, U-1286 - INFINTE - Institute for Translational Research in Inflammation, 59000, Lille, France.,Par'Immune, Bio-incubateur Eurasanté, 70 rue du Dr. Yersin, 59120, Loos-Lez-Lille, France
| | - Charlotte Izabelle
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014, Paris, France
| | - Sarah Gallet
- Univ. Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, UMR-S 1172, FHU 1000 Days for Health, Lille, France
| | - Sophie Le Poder
- UMR Virologie, INRAE, ANSES, École Nationale Vétérinaire d'Alfort, 94700, Maisons-Alfort, France
| | - Bernard Klonjkowski
- UMR Virologie, INRAE, ANSES, École Nationale Vétérinaire d'Alfort, 94700, Maisons-Alfort, France
| | - Markus Schwaninger
- Institute for Experimental and Clinical Pharmacology and Toxicology, Center for Brain, Behavior and Metabolism (CBBM), University of Lübeck, Lübeck, Germany.,DZHK (German Research Centre for Cardiovascular Research), Hamburg-Lübeck-Kiel, Hamburg, Germany
| | - Vincent Prevot
- Univ. Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, UMR-S 1172, FHU 1000 Days for Health, Lille, France
| | - Julie Dam
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014, Paris, France
| | - Ralf Jockers
- Université Paris Cité, Institut Cochin, INSERM, CNRS, 75014, Paris, France.
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3
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Empowering Melatonin Therapeutics with Drosophila Models. Diseases 2021; 9:diseases9040067. [PMID: 34698120 PMCID: PMC8544433 DOI: 10.3390/diseases9040067] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 09/14/2021] [Accepted: 09/22/2021] [Indexed: 12/15/2022] Open
Abstract
Melatonin functions as a central regulator of cell and organismal function as well as a neurohormone involved in several processes, e.g., the regulation of the circadian rhythm, sleep, aging, oxidative response, and more. As such, it holds immense pharmacological potential. Receptor-mediated melatonin function mainly occurs through MT1 and MT2, conserved amongst mammals. Other melatonin-binding proteins exist. Non-receptor-mediated activities involve regulating the mitochondrial function and antioxidant cascade, which are frequently affected by normal aging as well as disease. Several pathologies display diseased or dysfunctional mitochondria, suggesting melatonin may be used therapeutically. Drosophila models have extensively been employed to study disease pathogenesis and discover new drugs. Here, we review the multiple functions of melatonin through the lens of functional conservation and model organism research to empower potential melatonin therapeutics to treat neurodegenerative and renal diseases.
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Boutin JA, Legros C. The five dimensions of receptor pharmacology exemplified by melatonin receptors: An opinion. Pharmacol Res Perspect 2020; 8:e00556. [PMID: 31893125 PMCID: PMC6935684 DOI: 10.1002/prp2.556] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 12/03/2019] [Accepted: 12/03/2019] [Indexed: 12/22/2022] Open
Abstract
Receptology has been complicated with enhancements in our knowledge of G-protein-coupled-receptor (GPCR) biochemistry. This complexity is exemplified by the pharmacology of melatonin receptors. Here, we describe the complexity of GPCR biochemistry in five dimensions: (a) receptor expression, particularly in organs/tissues that are only partially understood; (b) ligands and receptor-associated proteins (interactome); (c) receptor function, which might be more complex than the known G-protein-coupled systems; (d) ligand bias, which favors a particular pathway; and (e) receptor dimerization, which might concern all receptors coexpressed in the same cell. Thus, receptor signaling might be modified or modulated, depending on the nature of the receptor complex. Fundamental studies are needed to clarify these points and find new ways to tackle receptor functionality. This opinion article emphasizes the global questions attached to new descriptions of GPCRs and aims to raise our awareness of the tremendous complexity of modern receptology.
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Affiliation(s)
- Jean A. Boutin
- Institut de Recherches Internationales ServierSuresnesFrance
| | - Céline Legros
- Institut de Recherches ServierCroissy‐sur‐SeineFrance
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5
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Dampening of neurotransmitter action: molecular similarity within the melatonin structure. Endocr Regul 2019; 52:199-207. [PMID: 31517615 DOI: 10.2478/enr-2018-0025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVES Melatonin initiates physiologic and therapeutic responses in various tissues through binding to poorly defined MT receptors regulated by G-proteins and purine nucleotides. Melatonin's interaction with other G-protein regulated receptors, including those of serotonin, is unclear. This study explores the potential for the interaction of melatonin with nucleotide and receptor ligand structures. METHODS The study uses a computational program to investigate relative molecular similarity by the comparative superimposition and quantitative fitting of molecular structures to adenine and guanine nucleotide templates. RESULTS A minimum energy melatonin conformer replicates the nucleotide fits of ligand structures that regulate Gαi and Gαq proteins via serotonin, dopamine, opioid, α-adrenoceptor, and muscarinic receptor classes. The same conformer also replicates the nucleotide fits of ligand structures regulating K+ and Ca2+ ion channels. The acyl-methoxy distance within the melatonin conformer matches a carbonyl-hydroxyl distance in guanine nucleotide. CONCLUSION Molecular similarity within the melatonin and ligand structures relates to the established effects of melatonin on cell receptors regulated by purine nucleotides in cell signal transduction processes. Pharmacologic receptor promiscuity may contribute to the widespread effects of melatonin.
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Souissi A, Yousfi N, Dabboubi R, Aloui G, Haddad M, Souissi N. Effect of acute melatonin administration on physiological response to prolonged exercise. BIOL RHYTHM RES 2019. [DOI: 10.1080/09291016.2019.1573462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Amine Souissi
- Research Unit Sport Performance, Health & Society, Higher Institute of Sport and Physical Education, Ksar Saîd University of “La Manouba”, Tunis, Tunisia
| | - Narimen Yousfi
- Research Laboratory “Sport Performance Optimization”, National Centre of Medicine and Science in Sport, Tunis, Tunisia
| | - Rim Dabboubi
- Laboratory of Biochemistry and Molecular Biology, Children’s Hospital of Tunis, Tunis, Tunisia
| | - Ghaith Aloui
- Research Unit Sport Performance, Health & Society, Higher Institute of Sport and Physical Education, Ksar Saîd University of “La Manouba”, Tunis, Tunisia
| | - Monoem Haddad
- Sports Science Program, College of Arts and Sciences, Qatar University, Doha, Qatar
| | - Nizar Souissi
- Research Unit Physical Activity, Sport & Health, National Observatory of Sports, Tunis, Tunisia
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Souissi A, Souissi N, Dabboubi R, Souissi N. Effect of melatonin on inflammatory response to prolonged exercise. BIOL RHYTHM RES 2018. [DOI: 10.1080/09291016.2018.1543638] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Amine Souissi
- Research Unit Sport Performance, Health & Society, Higher Institute of Sport and, Physical Education, Ksar Saîd University of “La Manouba”, Tunis, Tunisia
- Research Unit Physical Activity, Sport & Health, National Observatory of Sports, Tunis, Tunisia
| | - Nafaa Souissi
- Research Unit Physical Activity, Sport & Health, National Observatory of Sports, Tunis, Tunisia
| | - Rim Dabboubi
- Laboratory of Biochemistry and Molecular Biology, Children’s Hospital of Tunis, Tunis, Tunisia
| | - Nizar Souissi
- Research Unit Physical Activity, Sport & Health, National Observatory of Sports, Tunis, Tunisia
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Xu Z, Wu Y, Zhang Y, Zhang H, Shi L. Melatonin activates BK Ca channels in cerebral artery myocytes via both direct and MT receptor/PKC-mediated pathway. Eur J Pharmacol 2018; 842:177-188. [PMID: 30391348 DOI: 10.1016/j.ejphar.2018.10.032] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 10/17/2018] [Accepted: 10/24/2018] [Indexed: 11/28/2022]
Abstract
The pineal hormone melatonin is a neuroendocrine hormone with high membrane permeability that is involved in regulation of circadian rhythm of several biological functions. Large-conductance Ca2+-activated K+ (BKCa) channels are abundantly expressed in vascular smooth muscle cells and play an important role in vascular tone regulation. We investigated the mechanisms through which myocyte BKCa channels mediate effects of melatonin on cerebral arteries (CAs). Arterial contractility measurements showed that melatonin alone did not change vascular tone in CAs; however, it induced concentration-dependent vasodilation of phenylephrine-induced contraction in CAs. In the presence of the potent endothelial oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester, melatonin-elicited relaxation was significantly inhibited by iberiotoxin (BKCa channel blocker). Melatonin significantly increased BKCa currents but not voltage-gated K+ (KV) currents in whole-cell recordings. Melatonin decreased the amplitude of Ca2+ sparks and spontaneous transient outward currents (STOCs), however, a significant increase in open probability of BKCa channels was observed in both inside-out and cell-attached patch-clamp recordings. This melatonin-induced enhancement of BKCa channel activity was significantly suppressed by luzindole (melatonin MT1/MT2 receptor inhibitor), U73122 (phospholipase C (PLC) inhibitor), and Ro31-8220 (protein kinase C (PKC) inhibitor). Melatonin had no significant effects on sarcoplasmic reticulum release of Ca2+. These findings indicate that melatonin-induced vasorelaxation of CAs is partially attributable to direct (passing through the cell membrane) and indirect (via melatonin MT1/MT2 receptors-PLC-PKC pathway) activation of BKCa channels on CA myocytes.
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Affiliation(s)
- Zhaoxia Xu
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Ying Wu
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Yanyan Zhang
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Huirong Zhang
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China
| | - Lijun Shi
- Department of Exercise Physiology, Beijing Sport University, Beijing 100084, China.
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9
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Cecon E, Oishi A, Jockers R. Melatonin receptors: molecular pharmacology and signalling in the context of system bias. Br J Pharmacol 2018; 175:3263-3280. [PMID: 28707298 PMCID: PMC6057902 DOI: 10.1111/bph.13950] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 07/05/2017] [Accepted: 07/10/2017] [Indexed: 12/15/2022] Open
Abstract
Melatonin, N-acetyl-5-methoxytryptamine, an evolutionally old molecule, is produced by the pineal gland in vertebrates, and it binds with high affinity to melatonin receptors, which are members of the GPCR family. Among the multiple effects attributed to melatonin, we will focus here on those that are dependent on the activation of the two mammalian MT1 and MT2 melatonin receptors. We briefly summarize the latest developments on synthetic melatonin receptor ligands, including multi-target-directed ligands, and the characterization of signalling-biased ligands. We discuss signalling pathways activated by melatonin receptors that appear to be highly cell- and tissue-dependent, emphasizing the impact of system bias on the functional outcome. Different proteins have been demonstrated to interact with melatonin receptors, and thus, we postulate that part of this system bias has its molecular basis in differences of the expression of receptor-associated proteins including heterodimerization partners. Finally, bias at the level of the receptor, by the expression of genetic receptor variants, will be discussed to show how a modified receptor function can have an effect on the risk for common diseases like type 2 diabetes in humans. LINKED ARTICLES: This article is part of a themed section on Recent Developments in Research of Melatonin and its Potential Therapeutic Applications. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.16/issuetoc.
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Affiliation(s)
- Erika Cecon
- Institut CochinInserm, U1016ParisFrance
- CNRS UMR 8104ParisFrance
- Univ. Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Atsuro Oishi
- Institut CochinInserm, U1016ParisFrance
- CNRS UMR 8104ParisFrance
- Univ. Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Ralf Jockers
- Institut CochinInserm, U1016ParisFrance
- CNRS UMR 8104ParisFrance
- Univ. Paris Descartes, Sorbonne Paris CitéParisFrance
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10
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Lemley CO, Vonnahme KA. PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Alterations in uteroplacental hemodynamics during melatonin supplementation in sheep and cattle. J Anim Sci 2017; 95:2211-2221. [PMID: 28726984 DOI: 10.2527/jas.2016.1151] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Compromised placental function can result in fetal growth restriction which is associated with greater risk of neonatal morbidity and mortality. Large increases in transplacental nutrient and waste exchange, which support the exponential increase in fetal growth during the last half of gestation, are dependent primarily on the rapid growth and vascularization of the uteroplacenta. The amplitude of melatonin secretion has been associated with improved oxidative status and altered cardiovascular function in several mammalian species; however, melatonin mediated alterations of uteroplacental capacity in sheep and cattle are lacking. Therefore, our laboratories are examining uteroplacental blood flow and fetal development during maternal melatonin supplementation. Using a mid- to late-gestation ovine model of intrauterine growth restriction, we examined uteroplacental blood flow and fetal growth during supplementation with 5 mg/d of dietary melatonin. Maternal nutrient restriction decreased uterine arterial blood flow, while melatonin supplementation increased umbilical arterial blood flow compared with non-supplemented controls. Although melatonin treatment did not rescue fetal weight in nutrient restricted ewes; we observed disproportionate fetal size and fetal organ development. Elevated fetal concentrations of melatonin may result in altered blood flow distribution during important time points of development. These melatonin specific responses on umbilical arterial hemodynamics and fetal development may be partially mediated through vascular melatonin receptors. Recently, we examined the effects of supplementing Holstein heifers with 20 mg/d of dietary melatonin during the last third of gestation. Uterine arterial blood flow was increased by 25% and total serum antioxidant capacity was increased by 43% in melatonin supplemented heifers vs. non-supplemented controls. In addition, peripheral concentrations of progesterone were decreased in melatonin supplemented heifers vs. non-supplemented controls. Using an in vitro model, melatonin treatment increased the activity of cytochrome P450 2C, a progesterone inactivating enzyme, which was blocked by treatment with the melatonin receptor antagonist, luzindole. Elucidating the consequences of specific hormonal supplements on the continual plasticity of placental function will allow us to determine important endogenous mediators of offspring growth and development.
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11
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Zhao T, Zhang H, Jin C, Qiu F, Wu Y, Shi L. Melatonin mediates vasodilation through both direct and indirect activation of BK Ca channels. J Mol Endocrinol 2017; 59:219-233. [PMID: 28676563 DOI: 10.1530/jme-17-0028] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/03/2017] [Indexed: 01/14/2023]
Abstract
Melatonin, synthesized primarily by the pineal gland, is a neuroendocrine hormone with high membrane permeability. The vascular effects of melatonin, including vasoconstriction and vasodilation, have been demonstrated in numerous studies. However, the mechanisms underlying these effects are not fully understood. Large-conductance Ca2+-activated K+ (BKCa) channels are expressed broadly on smooth muscle cells and play an important role in vascular tone regulation. This study explored the mechanisms of myocyte BKCa channels and endothelial factors underlying the action of melatonin on the mesenteric arteries (MAs). Vascular contractility and patch-clamp studies were performed on myocytes of MAs from Wistar rats. Melatonin induced significant vasodilation on MAs. In the presence of Nω-nitro-l-arginine methyl ester (l-NAME), a potent endothelial oxide synthase (eNOS) inhibitor, melatonin elicited concentration-dependent relaxation, with lowered pIC50 The effect of melatonin was significantly attenuated in the presence of BKCa channel blocker iberiotoxin or MT1/MT2 receptor antagonist luzindole in both (+) l-NAME and (-) l-NAME groups. In the (+) l-NAME group, iberiotoxin caused a parallel rightward shift of the melatonin concentration-relaxation curve, with pIC50 lower than that of luzindole. Both inside-out and cell-attached patch-clamp recordings showed that melatonin significantly increased the open probability, mean open time and voltage sensitivity of BKCa channels. In a cell-attached patch-clamp configuration, the melatonin-induced enhancement of BKCa channel activity was significantly suppressed by luzindole. These findings indicate that in addition to the activation of eNOS, melatonin-induced vasorelaxation of MAs is partially attributable to its direct (passing through the cell membrane) and indirect (via MT1/MT2 receptors) activation of the BKCa channels on mesenteric arterial myocytes.
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MESH Headings
- Animals
- Gene Expression
- Ion Channel Gating/drug effects
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/agonists
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/genetics
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/metabolism
- Male
- Melatonin/metabolism
- Melatonin/pharmacology
- Muscle, Smooth, Vascular/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Rats
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Vasodilation/drug effects
- Vasodilation/genetics
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Affiliation(s)
- T Zhao
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - H Zhang
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - C Jin
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - F Qiu
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - Y Wu
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
| | - L Shi
- Department of Exercise PhysiologyBeijing Sport University, Beijing, China
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Laskowski M, Andersson C, Eliasson E, Golubinskaya V, Nilsson H. Potassium-Channel-Independent Relaxing Influence of Adipose Tissue on Mouse Carotid Artery. J Vasc Res 2017; 54:51-57. [PMID: 28334715 DOI: 10.1159/000458421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 01/27/2017] [Indexed: 11/19/2022] Open
Abstract
Since the cardiovascular consequences of obesity reportedly vary in different types of obesity, we investigated the influence of adipose tissue from different locales on the phenylephrine-induced tone of the mouse carotid artery. Vessels were mounted in a Mulvany-Halpern-type wire myograph, and adipose tissue, from the back (brown) or mesenteric or inguinal subcutaneous (white), was placed around the artery. Contractile responses to phenylephrine were not affected by brown adipose tissue but were reduced (p < 0.001) by either type of white adipose tissue, with no difference between the 2 locales. The relaxing effect persisted in the presence of the Kv7 channel inhibitor XE991 (10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone), the KATP channel inhibitor glibenclamide (1 µM), or the KV channel inhibitor 4-amino pyridine (1 mM), as well as after elevation of the extracellular potassium concentration to 30 mM. Contractions of rat carotid artery were equally reduced by mouse and rat subcutaneous adipose tissue. Thus, white, but not brown, adipose tissue reduces the adrenergic contractions of the carotid artery with no differences between the locales of origin, and the effect appears largely independent of potassium channels.
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Affiliation(s)
- Marta Laskowski
- Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
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13
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Georgiev T, Tolekova A, Kalfin R, Hadzhibozheva P. Short-term administration of melatonin or ghrelin on diabetic rats: effects on angiotensin II and vasopressin-induced uterine contractility. Physiol Res 2016; 66:125-133. [PMID: 27782742 DOI: 10.33549/physiolres.933337] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The aim of the present study was to investigate the effects of Angiotensin II (Ang II) and Arginin-Vasopressin (AVP) on contractility of non-pregnant uterus in diabetic Wistar rats and to explore whether one-week administration of Melatonin (MLT) or Ghrelin (GHR) will change the response of diabetic uterine muscle to AngII and AVP. Uterine horns, prepared by the method of isolated tissues were investigated as well as glycemic profile, blood pressure and body weight. The research of smooth muscle contractions was made by a new method of analysis, characterizing in detail the various phases of the myometrial activity. Differences in the development of the peptide-mediated smooth muscle contractions depending on the phase of the estrous cycle were observed. Experimental diabetes had a pronounced negative effect on force and time-parameters of AngII and AVP-stimulated uterine contractions. Administration of GHR or MLT had a beneficial effect on the glycemic status of diabetic rats and partially improved the response of uterine preparations to the peptides. The application of MLT increased both force and time-parameters of Ang II-and AVP-stimulated uterine contractions while treatment with GHR increased power characteristics and shortened contraction and relaxation of the smooth muscle process.
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Affiliation(s)
- T Georgiev
- Department of Physiology, Pathophysiology and Pharmacology, Medical Faculty, Trakia University, Stara Zagora, Bulgaria.
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14
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Fathollahi A, Daneshgari F, Hanna-Mitchell AT. Melatonin and Its Role in Lower Urinary Tract Function: An Article Review. Curr Urol 2015; 8:113-8. [PMID: 26889129 DOI: 10.1159/000365701] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 02/20/2015] [Indexed: 01/19/2023] Open
Abstract
This article reviewed the results of studies done on animals that assessed effects of melatonin on bladder function. Melatonin does not change strip relaxation on its own. However, pre-treatment with melatonin decreases contractile responses induced by phenylephrine, acetylcholine, bethanechol and KCl in a dose-dependent manner. The contractile responses induced by the direct calcium channel openers are significantly decreased by melatonin pre-treatment. It also binds to Ca(2+)-activated calmodulin, and prevents it from activating myosin light-chain kinase. It may have direct effects on ion channels which are responsible for regulating bladder contraction. Its other mode of action on bladder occurs via the brain GABAA receptor. Melatonin is an antioxidant. In bladder, treatment with melatonin prevents elevations in malondialdehyde levels, reverses changes in glutathione levels, and decreases myeloperoxidase levels compared with oxidative injury. It can normalize age induced bladder dysfunction through its antioxidant effects, inhibiting smooth muscle contractility directly and restoring impaired contractility via normalization of Ca(2+) handling and sensitizations pathways. It attenuates the severity of cystitis and inflammation. Mast cell proliferation and activation are increased in cystitis, but decrease by melatonin treatment. Also, there is a decrease in expression levels of pro-inflammatory cytokines after melatonin treatment.
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Affiliation(s)
- Ali Fathollahi
- Urology Institute, Case Western Reserve University, Cleveland, OH., USA
| | - Firouz Daneshgari
- Urology Institute, Case Western Reserve University, Cleveland, OH., USA
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Zeynalov E, Rezvani N, Miyazaki C, Liu X, Littleton-Kearney MT. Reproductive senescence blunts response of estrogen receptor-α expression to estrogen treatment in rat post-ischemic cerebral microvessels. PLoS One 2014; 9:e102194. [PMID: 25010766 PMCID: PMC4092076 DOI: 10.1371/journal.pone.0102194] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 06/13/2014] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Several studies demonstrate that estrogen treatment improves cerebral blood flow in ischemic brain regions of young ovariectomized (OVX) rats. Estrogen receptor-α (ER-α) may mediate estrogen's beneficial actions via its effects on the cerebral microvasculature. However, estrogen-derived benefit may be attenuated in aged, reproductively senescent (RS) rats. Our goal was to determine the effects of aging, estrogen deprivation and estrogen repletion with oral conjugated estrogens (CE) on postischemic cerebral microvascular protein expression of ER-α and ER-β. METHODS Fisher-344 (n = 37) female rats were randomly divided into the following groups: OVX, OVX CE-treated, RS untreated, and RS CE-treated. After 30 days pretreatment with CE (0.01 mg/kg) rats were subjected to 15 min. transient global cerebral ischemia. Non-ischemic naïve, OVX and RS rats were used as controls. Expression of ER-α and ER-β in isolated cortical cerebral microvessels (20 to 100 µm in diameter) was assessed using Western blot and immunohistochemistry techniques. RESULTS Age and reproductive status blunted nonischemic ER-α expression in microvessels of OVX rats (0.31 ± 0.05) and RS rats (0.33 ± 0.06) compared to naïve rats (0.45 ± 0.02). Postischemic microvascular expression of ER-α in OVX rats (0.01 ± 0.0) was increased by CE treatment (0.04 ± 0.01). Expression of ER-α in microvessels of RS rats (0.03 ± 0.02) was unaffected by CE treatment (0.01 ± 0.02). Western blot data are presented as a ratio of ER-α or ER-β proteins to β-actin and. Oral CE treatment had no effect on ER-β expression in postischemic microvessels of OVX and RS rats. Statistical analysis was performed by One-Way ANOVA and a Newman-Keuls or Student's post-hoc test. CONCLUSION Chronic treatment with CE increases ER-α but not ER-β expression in cerebral microvessels of OVX rats. Aging appears to reduce the normal ability of estrogen to increase ER-α expression in postischemic cerebral microvessels.
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Affiliation(s)
- Emil Zeynalov
- Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
- * E-mail:
| | - Niloofar Rezvani
- Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Chikao Miyazaki
- Johns Hopkins University School of Medicine, Department of Anesthesiology and Critical Care Medicine, Baltimore, Maryland, United States of America
| | - Xiaoguang Liu
- Johns Hopkins University School of Medicine, Department of Anesthesiology and Critical Care Medicine, Baltimore, Maryland, United States of America
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Taylor AC, Horvat-Gordon M, Moore A, Bartell PA. The effects of melatonin on the physical properties of bones and egg shells in the laying hen. PLoS One 2013; 8:e55663. [PMID: 23468846 PMCID: PMC3585294 DOI: 10.1371/journal.pone.0055663] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 12/29/2012] [Indexed: 11/18/2022] Open
Abstract
Laying hens often experience unbalanced calcium utilization which can cause deficiencies in bone and egg mineralization. Because melatonin has been shown to affect bone mineralization in other animals, we examined whether treating hens with melatonin would affect eggshell thickness and improve skeletal performance, thereby reducing skeletal and egg shell defects. Birds were given a diet containing either low (30 µg/kg), medium (300 µg/kg), or high (3 mg/kg) concentrations of melatonin, or control feed through approximately one laying cycle. We examined the weight, length, and strength of egg, femur, tibia, and keel. Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls. Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin. Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin. Our data suggest that melatonin may affect the allocation of calcium to bone at the expense of egg shell mineralization.
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Affiliation(s)
- Alexander C. Taylor
- Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Intercollege Graduate Degree Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Maria Horvat-Gordon
- Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Ashli Moore
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Paul A. Bartell
- Department of Animal Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Intercollege Graduate Degree Program in Physiology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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Ciosek J, Drobnik J. Function of the hypothalamo-neurohypophysial system in rats with myocardial infarction is modified by melatonin. Pharmacol Rep 2012; 64:1442-54. [DOI: 10.1016/s1734-1140(12)70942-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 08/03/2012] [Indexed: 01/19/2023]
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18
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Shukla P, Sun C, O'Rourke ST. Melatonin inhibits nitric oxide signaling by increasing PDE5 phosphorylation in coronary arteries. Am J Physiol Heart Circ Physiol 2012; 303:H1418-25. [PMID: 23086989 DOI: 10.1152/ajpheart.00211.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Melatonin inhibits nitric oxide (NO)-induced relaxation of coronary arteries. We tested the hypothesis that melatonin increases the phosphorylation of phosphodiesterase 5 (PDE5), which increases the activity of the enzyme and thereby decreases intracellular cGMP accumulation in response to NO and inhibits NO-induced relaxation. Sodium nitroprusside (SNP) and 8-Br-cGMP caused concentration-dependent relaxation of isolated coronary arteries suspended in organ chambers for isometric tension recording. In the presence of melatonin, the concentration-response curve to SNP, but not 8-Br-cGMP, was shifted to the right. The effect of melatonin on SNP-induced relaxation was abolished in the presence of the PDE5 inhibitors zaprinast and sildenafil. Melatonin markedly inhibited the SNP-induced increase in intracellular cGMP in coronary arteries, an effect that was also abolished by zaprinast. Treatment of coronary arteries with melatonin caused a nearly fourfold increase in the phosphorylation of PDE5, which increased the catalytic activity of the enzyme and thereby increased the degradation of cGMP to inactive 5'-GMP. Melatonin-induced PDE5 phosphorylation was markedly attenuated in the presence of the PKG1 inhibitors DT-2 or Rp-8-Br-PET-cGMPS and in those arteries in which PKG1 expression was first downregulated by 24-h incubation with SNP before exposure to melatonin. The selective MT(2) receptor antagonist 4-phenyl-2-propionamidotetralin completely blocked the stimulatory effect of melatonin on PDE5 phosphorylation as well as the inhibitory effect of melatonin on SNP-induced relaxation and intracellular cGMP. Thus, in coronary arteries, melatonin acts via MT(2) receptors and PKG1 to increase PDE5 phosphorylation, resulting in decreased cGMP accumulation in response to NO and impaired NO-induced vasorelaxation.
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Affiliation(s)
- Praveen Shukla
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, 58108-6050, USA
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Velarde E, Alonso-Gómez AL, Azpeleta C, Isorna E, De Pedro N, Delgado MJ. Melatonin effects on gut motility are independent of the relaxation mediated by the nitrergic system in the goldfish. Comp Biochem Physiol A Mol Integr Physiol 2011; 159:367-71. [PMID: 21539928 DOI: 10.1016/j.cbpa.2011.01.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 12/27/2010] [Accepted: 01/17/2011] [Indexed: 11/19/2022]
Abstract
Melatonin is a key neuroendocrine transducer in the circadian organization of vertebrates. However, its role in gastrointestinal physiology has not been explored in depth. In goldfish, a role for melatonin as a modulator of intestinal motility has been reported, whereby it attenuates the cholinergic contraction. The aim of the present work was to investigate this relaxation induced by melatonin in the gut smooth muscle of the goldfish, studying the possible involvement of nitric oxide. An in vitro model of isolated goldfish intestine was used to test the effects on intestinal motility. The addition of melatonin (10 pM-100 μM) to the organ bath relaxed acetylcholine- and serotonin-stimulated gut strips, but no effect was observed on KCl-contracted preparations. The addition of L-NAME (nitric oxide synthase inhibitor) increased the amplitude of the spontaneous slow waves, while sodium nitroprusside (SNP, nitric oxide donor) abolished them. All these results support a role for the nitrergic system in goldfish gut motility. However, neither L-NAME, nor SNP nor the nitric oxide precursor, l-arginine, modified the melatonin relaxing effect. These results highlight the existence of a basal nitrergic tone in the gut of goldfish, where melatonin would exert a calcium-dependent, nitric oxide-independent relaxing effect on serotonergic and cholinergic contraction.
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Affiliation(s)
- Elena Velarde
- Department of Physiology (Animal Physiology II), Faculty of Biology, Complutense University of Madrid, Madrid, Spain
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Shiu SYW, Pang B, Tam CW, Yao KM. Signal transduction of receptor-mediated antiproliferative action of melatonin on human prostate epithelial cells involves dual activation of Gα(s) and Gα(q) proteins. J Pineal Res 2010; 49:301-11. [PMID: 20695976 DOI: 10.1111/j.1600-079x.2010.00795.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin has been shown to inhibit the proliferation of malignant and transformed human prostate epithelial cells by transcriptional up-regulation of p27(Kip1) expression via MTNR1A receptor-mediated activation of protein kinase A (PKA) and protein kinase C (PKC) in parallel. Given that melatonin MTNR1A receptor is a G protein-coupled receptor, this study was conducted to identify the specific G proteins that mediate the antiproliferative action of melatonin on human prostate epithelial cells. In 22Rv1 and RWPE-1 cells, knockdown of either Gα(s) or Gα(q) , but not Gα(i2) expression by RNA interference, abrogated the effects of melatonin on p27(Kip1) and cell proliferation. Conversely, cellular overexpression of activated mutants of Gα(s) and Gα(q) in 22Rv1 and RWPE-1 cells mimicked the effects of melatonin on prostate epithelial cell antiproliferation by increasing p27(Kip1) expression through downstream activation of PKA and PKC in parallel. Moreover, melatonin or 2-iodomelatonin induced elevation of adenosine-3',5'-cyclic monophosphate (cAMP) in 22Rv1 and RWPE-1 cells. The effects of 2-iodomelatonin on cAMP were blocked by the nonselective MTNR1A/MTNR1B receptor antagonist luzindole but were not affected by the selective MTNR1B receptor antagonist 4-phenyl-2-propionamidotetraline (4-P-PDOT). Furthermore, knockdown of Gα(s) mitigated the stimulatory effects of 2-iodomelatonin on cAMP. Collectively, the data demonstrated, for the first time, functional coupling of MTNR1A receptor to Gα(s) in cancerous or transformed human cells expressing endogenous melatonin receptors. Our results also showed that dual activation of Gα(s) and Gα(q) proteins is involved in the signal transduction of MTNR1A receptor-mediated antiproliferative action of melatonin on human prostate epithelial cells.
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Affiliation(s)
- Stephen Y W Shiu
- Department of Physiology, The University of Hong Kong, Hong Kong, China.
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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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Oxenkrug GF, Summergrad P. Ramelteon attenuates age-associated hypertension and weight gain in spontaneously hypertensive rats. Ann N Y Acad Sci 2010; 1199:114-20. [DOI: 10.1111/j.1749-6632.2009.05355.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Melatonin acts both as a hormone of the pineal gland and as a local regulator molecule in various tissues. Quantities of total tissue melatonin exceed those released from the pineal. With regard to this dual role, to the orchestrating, systemic action on various target tissues, melatonin is highly pleiotropic. Numerous secondary effects result from the control of the circadian pacemaker and, in seasonal breeders, of the hypothalamic/pituitary hormonal axes. In mammals, various binding sites for melatonin have been identified, the membrane receptors MT(1) and MT(2), which are of utmost chronobiological importance, ROR and RZR isoforms as nuclear receptors from the retinoic acid receptor superfamily, quinone reductase 2, calmodulin, calreticulin, and mitochondrial binding sites. The G protein-coupled receptors (GPCRs) MT(1) and MT(2) are capable of parallel or alternate signaling via different Galpha subforms, in particular, Galpha(i) (2/) (3) and Galpha(q), and via Gbetagamma, as well. Multiple signaling can lead to the activation of different cascades and/or ion channels. Melatonin frequently decreases cAMP, but also activates phospholipase C and protein kinase C, acts via the MAP kinase and PI3 kinase/Akt pathways, modulates large conductance Ca(2+)-activated K(+) and voltage-gated Ca(2+) channels. MT(1) and MT(2) can form homo and heterodimers, and MT(1) interacts with other proteins in the plasma membrane, such as an orphan GPCR, GPR50, and the PDZ domain scaffolding protein MUPP1, effects which negatively or positively influence signaling capacity. Cross-talks between different signaling pathways, including influences of the membrane receptors on nuclear binding sites, are discussed. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.
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Affiliation(s)
- Rüdiger Hardeland
- Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Göttingen, Germany.
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Das R, Balonan L, Ballard HJ, Ho S. Chronic hypoxia inhibits the antihypertensive effect of melatonin on pulmonary artery. Int J Cardiol 2008; 126:340-5. [PMID: 17590454 DOI: 10.1016/j.ijcard.2007.04.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2006] [Accepted: 04/01/2007] [Indexed: 11/21/2022]
Abstract
Exposure of animals to chronic hypoxia induces pulmonary vascular remodeling leading to pulmonary hypertension. Melatonin, the principal hormone of the pineal gland, is known to have an inhibitory effect on rat vascular reactivity. This study examined the effect of chronic hypoxia on the influence of melatonin on the vasoreactivity of the pulmonary artery. The inhibitory effect of melatonin on the phenylephrine-induced constriction in normoxia-adapted rings (101.5+/-4% versus 82.2+/-4%) in the presence or absence of melatonin, respectively) was lost following chronic hypoxic treatment (100.2+/-4% versus 102.2+/-2%) and this effect was independent of the endothelium. Melatonin also significantly enhanced the relaxant response to acetylcholine of the pulmonary arterial rings from normoxic rats (34.76+/-5.67% versus 53.82+/-4.736%) in the absence or presence of melatonin, respectively). In contrast, melatonin had no significant effect (21.71+/-1.37% versus 23.51+/-6.891%) on the relaxant response to acetylcholine of the pulmonary arterial rings from chronic hypoxia-adapted rats. Pre-treatment with melatonin (10(-4) M) showed no significant effect on the vasorelaxation by the nitric oxide donor; sodium nitroprusside (10(-7)-10(-5) M). The melatonin-induced changes were blocked by the melatonergic-receptor antagonist luzindole (2x10(-6) M). The results from our study confirm the presence of melatonergic receptors on the pulmonary trunk of rats and also suggest that the modulatory role of melatonin on the vasoreactivity of pulmonary trunk does not involve the nitric oxide pathway. Most importantly, our results show that development of pulmonary hypertension in rats is associated with the loss of the vasorelaxant influence of melatonin.
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Affiliation(s)
- Rapti Das
- Division of Health and Applied Science, School of Professional and Continuing Education, The University of Hong Kong, Pokfulam, Hong Kong, SAR
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25
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Wronka M, Maleszewska M, Stepińska U, Markowska M. Diurnal differences in melatonin effect on intracellular Ca2+ concentration in chicken spleen leukocytes in vitro. J Pineal Res 2008; 44:134-40. [PMID: 18289164 DOI: 10.1111/j.1600-079x.2007.00500.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Melatonin plays a pleiotropic role in the immune system of mammals and birds. Endogenous and exogenous melatonin modulates lymphocyte proliferation via specific MT(1), MT(2) and Mel(1c) membrane receptors, although the mechanisms behind this process are poorly understood. The diurnal changes in the expression and function of melatonin membrane receptors within the immune system have so far received little attention. We investigated the day/night differences in melatonin membrane receptor mRNA expression in chicken lymphoid organs and cultured splenocytes and examined the in vitro effect of melatonin and 2-iodomelatonin on the intracellular Ca(2+) concentration ([Ca(2+)](i)) in chicken splenocytes. In whole organs, expression of all subtypes of Mel membrane receptors was observed, and the level did not change significantly with the time of day. Interestingly, we observed a significant increase in the expression of the transcripts of all receptor subtypes in cultured splenocytes isolated at night compared with cells obtained during the day. In chicken spleen leukocytes isolated during the day, melatonin and 2-iodomelatonin increased [Ca(2+)](i), with only 2-iodomelatonin being effective in the 'night' cells. Luzindole modulated the [Ca(2+)](i) increase caused by melatonin receptor agonists: it potentiated the stimulatory effect of melatonin during the day, but counteracted that evoked by 2-iodomelatonin at night. The results of this study demonstrate that melatonin can induce changes in [Ca(2+)](i) in chicken spleen leukocytes that should modulate proliferation. The effect of melatonin on [Ca(2+)](i) is less pronounced at night, possibly caused by receptor desensitization.
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Affiliation(s)
- Michał Wronka
- Department of Animal Physiology, Faculty of Biology, Warsaw University, Warsaw, Poland
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26
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Liu LY, Hoffman GE, Fei XW, Li Z, Zhang ZH, Mei YA. Delayed rectifier outward K+ current mediates the migration of rat cerebellar granule cells stimulated by melatonin. J Neurochem 2007; 102:333-44. [PMID: 17561939 DOI: 10.1111/j.1471-4159.2007.04669.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Melatonin (MT) may work as a neuromodulator through the associated MT receptors in the central nervous system. Previously, our studies have shown that MT increased the I(K) current via a G protein-related pathway. In the present study, patch-clamp whole-cell recording, transwell migration assays and organotypic cerebellar slice cultures were used to examine the effect of MT on granule cell migration. MT increased the I(K) current amplitude and migration of granule cells. Meanwhile, TEA, the I(K) channel blocker, decreased the I(K) current and slowed the migration of granule cells. Furthermore, the effects of MT on the I(K) current and cell migration were not abolished by pre-incubation with P7791, a specific antagonist of MT(3)R, but were eliminated by the application of the MT(2)R antagonists K185 and 4-P-PDOT. I(K) current and cell migration were decreased by the application of dibutyryl cyclic AMP (dbcAMP), which was in contrast to the MT effect on the I(K) current and cell migration. Incubation with dbcAMP essentially blocked the MT-induced increasing effect. Moreover, incubation of isolated cell cultures in the MT-containing medium also decreased the cAMP immunoreactivity in the granule cells. It is concluded, therefore, that I(K) current, downstream of a cAMP transduction pathway, mediates the migration of rat cerebellar granule cells stimulated by MT.
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MESH Headings
- Animals
- Animals, Newborn
- Bucladesine/pharmacology
- Cell Differentiation/drug effects
- Cell Differentiation/physiology
- Cell Movement/drug effects
- Cell Movement/physiology
- Cells, Cultured
- Cerebellar Cortex/cytology
- Cerebellar Cortex/growth & development
- Cerebellar Cortex/metabolism
- Culture Media, Conditioned/pharmacology
- Cyclic AMP/metabolism
- Melatonin/metabolism
- Melatonin/pharmacology
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Models, Neurological
- Neurons/cytology
- Neurons/drug effects
- Neurons/metabolism
- Organ Culture Techniques
- Patch-Clamp Techniques
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Voltage-Gated/drug effects
- Potassium Channels, Voltage-Gated/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Melatonin, MT2/antagonists & inhibitors
- Receptor, Melatonin, MT2/metabolism
- Receptors, Melatonin/antagonists & inhibitors
- Receptors, Melatonin/metabolism
- Signal Transduction/physiology
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Affiliation(s)
- Lin-Yun Liu
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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Silva CLM, Tamura EK, Macedo SMD, Cecon E, Bueno-Alves L, Farsky SHP, Ferreira ZS, Markus RP. Melatonin inhibits nitric oxide production by microvascular endothelial cells in vivo and in vitro. Br J Pharmacol 2007; 151:195-205. [PMID: 17375079 PMCID: PMC2013957 DOI: 10.1038/sj.bjp.0707225] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE We have previously shown that melatonin inhibits bradykinin-induced NO production by endothelial cells in vitro. The purpose of this investigation was to extend this observation to an in vivo condition and to explore the mechanism of action of melatonin. EXPERIMENTAL APPROACH RT-PCR assays were performed with rat cultured endothelial cells. The putative effect of melatonin upon arteriolar tone was investigated by intravital microscopy while NO production by endothelial cells in vitro was assayed by fluorimetry, and intracellular Ca(2+) measurements were assayed by confocal microscopy. KEY RESULTS No expression of the mRNA for the melatonin synthesizing enzymes, arylalkylamine N-acetyltransferase and hydroxyindole-O-methyltransferase, or for the melatonin MT(2) receptor was detected in microvascular endothelial cells. Melatonin fully inhibited L-NAME-sensitive bradykinin-induced vasodilation and also inhibited NO production induced by histamine, carbachol and 2-methylthio ATP, but did not inhibit NO production induced by ATP or alpha, beta-methylene ATP. None of its inhibitory effects was prevented by the melatonin receptor antagonist, luzindole. In nominally Ca(2+)-free solution, melatonin reduced intracellular Ca(2+) mobilization induced by bradykinin (40%) and 2-methylthio ATP (62%) but not Ca(2+) mobilization induced by ATP. CONCLUSIONS AND IMPLICATIONS We have confirmed that melatonin inhibited NO production both in vivo and in vitro. In addition, the melatonin effect was selective for some G protein-coupled receptors and most probably reflects an inhibition of Ca(2+) mobilization from intracellular stores.
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Affiliation(s)
- C L M Silva
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo São Paulo, Brazil
| | - E K Tamura
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo São Paulo, Brazil
| | - S M D Macedo
- Departamento de Análises Clínicas e Toxicológicas, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo São Paulo, Brazil
| | - E Cecon
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo São Paulo, Brazil
| | - L Bueno-Alves
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo São Paulo, Brazil
| | - S H P Farsky
- Departamento de Análises Clínicas e Toxicológicas, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo São Paulo, Brazil
| | - Z S Ferreira
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo São Paulo, Brazil
| | - R P Markus
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo São Paulo, Brazil
- Author for correspondence:
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le Grand SM, Patumraj S, Phansuwan-Pujito P, Srikiatkhachorn A. Melatonin inhibits cortical spreading depression-evoked trigeminal nociception. Neuroreport 2006; 17:1709-13. [PMID: 17047458 DOI: 10.1097/wnr.0b013e3280101207] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This study was conducted to determine the effect of melatonin on cortical spreading depression-evoked trigeminovascular nociception. Melatonin (20 or 40 mg/kg) or saline was given to Wistar rats. KCl was placed on the cortical surface to elicit the cortical spreading depression. Cortical blood flow was monitored and ultrastructure of cerebral microvessels was studied. The medulla and cervical cord were removed for Fos and nitric oxide synthase immunohistochemical study. The results showed that melatonin pretreatment significantly minimized the cortical spreading depression-evoked cerebral hyperaemia and attenuated the cortical spreading depression-induced microvascular changes. Pretreatment with melatonin also reduced the number of Fos and nitric oxide synthase immunoreactive cells in the trigeminal nucleus caudalis. The results of this study suggest that melatonin can attenuate the process of trigeminovascular nociception induced by cortical spreading depression.
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Affiliation(s)
- Supang M le Grand
- Department of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
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29
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Abstract
Endothelial cell function is a major player on the regulation of both vascular tonus and permeability. Activation of nitric oxide synthase (NOS) by bradykinin is one physiological pathway for the well-known vascular relaxation mediated by endothelial-derived nitric oxide (NO). In this study we investigated if melatonin, which is known to modulate endothelial cell function and NO production in other tissues, is able to impair bradykinin-induced NO production in vitro. Rat microvascular endothelial cells were incubated with fluorescent dyes to detect either NO or Ca2+. In addition, cGMP levels were measured by enzyme immunoassay. We found that while bradykinin (1-100 nm) increased both cytosolic Ca2+ and NO production, melatonin (1 nm) abolished this NO production but not cytosolic Ca2+ elevation. N-acetylserotonin (0.1 and 1 nm) had the same effect, while the selective agonist for MT3 receptors (5-MCA-NAT, 1 nm) had no effect. Moreover, nonselective and MT2-selective antagonists did not alter the effect of melatonin, suggesting that it is not mediated by MT melatonin receptors. A possible direct inhibition of calmodulin was also discarded as melatonin did not mimic the effect of calmidazolium on cytosolic Ca2+. Melatonin also abolished cGMP production induced by 1 microm bradykinin, indicating that the NO downstream effect is impaired. Thus, here we show that melatonin reduces NO production induced by bradykinin by a mechanism upstream to the interaction of Ca2+ -calmodulin with NOS. Moreover, this effect might be the basis of the diurnal variation in endothelial cell function.
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Affiliation(s)
- Eduardo K Tamura
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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30
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Abstract
In addition to its antioxidative effects melatonin acts through specific nuclear and plasma membrane receptors. To date, two G-protein coupled melatonin membrane receptors, MT(1) and MT(2), have been cloned in mammals, while the newly purified MT(3) protein belongs to the family of quinone reductases. Screening studies have shown that various tissues of rodents express MT(1) and/or MT(2) melatonin receptors. In humans, melatonin receptors were also detected in several organs, including brain and retina, cardiovascular system, liver and gallbladder, intestine, kidney, immune cells, adipocytes, prostate and breast epithelial cells, ovary/granulosa cells, myometrium, and skin. This review summarizes the data published so far about MT(1) and MT(2) receptors in human tissues and human cells. Established and putative functions of melatonin after receptor activation as well as the clinical relevance of these findings will be discussed.
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MESH Headings
- Adipocytes/metabolism
- Animals
- Biliary Tract/metabolism
- Breast/metabolism
- Cardiovascular System/metabolism
- Central Nervous System/metabolism
- Female
- Gastrointestinal Tract/metabolism
- Genitalia, Female/metabolism
- Humans
- Immune System/metabolism
- Male
- Melatonin/metabolism
- Polymorphism, Genetic
- Prostate/metabolism
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Receptor, Melatonin, MT2/genetics
- Receptor, Melatonin, MT2/metabolism
- Signal Transduction
- Skin/cytology
- Skin/metabolism
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Affiliation(s)
- C Ekmekcioglu
- Department of Physiology, Center for Physiology and Pathophysiology, Medical University Vienna, Schwarzpanierstrasse 17, A-1090 Vienna, Austria.
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31
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Kurcer Z, Sahna E, Olmez E. Vascular Reactivity to Various Vasoconstrictor Agents and Endothelium-Dependent Relaxations of Rat Thoracic Aorta in the Long-Term Period of Pinealectomy. J Pharmacol Sci 2006; 101:329-34. [PMID: 16921237 DOI: 10.1254/jphs.fp0060380] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
In this study, the effects of reduced melatonin concentrations in the long-term period of pinealectomy on mean arterial blood pressure (BP) and vascular responses in isolated rat thoracic aorta were investigated. Rats were pinealectomized (Px) two months before the beginning of the studies. Rings of endothelium-intact and -denuded rat arteries were mounted in isolated tissue baths for the measurements of isometric contractile force. No significant difference was determined between the arterial BP of Px (88.1 +/- 1.9 mmHg) and control (83.8 +/- 1.2 mmHg) rats. All arteries isolated from control and Px rats showed essentially identical contractions in response to phenylephrine, serotonin, calcium, clonidine, vasopressin, and angiotensin-II. Only endothelin-1 (ET-1)-induced contractions in the endothelium-denuded vessels isolated from Px rats were found to be increased to some extent. Pinealectomy did not affect acetylcholine or sodium nitroprusside-induced relaxation in the rat aorta either. These data suggest that reduced melatonin levels two months after pinealectomy did not modify either the vascular reactivity to various vasoconstrictor agents except the partially increased contractile responses to ET-1 in the endothelium-denuded thoracic aortas of Px rats or the endothelium-dependent and -independent relaxations in rat thoracic aorta. Restoration of the increased vascular responses to some vasoconstrictor agents, which were reported previously, may be the reason of why the hypertension is temporary following pinealectomy.
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Affiliation(s)
- Zehra Kurcer
- Department of Pharmacology, Faculty of Medicine, Harran University, Sanliurfa, Turkey.
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32
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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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33
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Karachentseva OV, Yartsev VN, Dvoretsky DP, Zhdanova IV. Melatonin-evoked potentiation of the juvenile rat tail artery neurogenic reactivity depends on degree of the change in the reactivity. ACTA PHYSIOLOGICA SCANDINAVICA 2005; 185:99-107. [PMID: 16168004 DOI: 10.1111/j.1365-201x.2005.01472.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
AIM Dependence of the melatonin-evoked potentiation of the rat tail artery neurogenic reactivity on degree of the change in the reactivity was studied. METHOD Electrical field stimulation-evoked contractile response of the juvenile rat tail artery segment under isometric conditions was recorded. 0.1 mum melatonin was administered after the change in the response produced both spontaneously and by acidification (pH 6.6) or alkalinization (pH 7.8) of the solution. RESULTS During the course of experiment, the contraction force continuously declined, being reduced by 12 +/- 5, 24 +/- 7 and 32 +/- 6% at 20, 70, and 170 min after beginning of experiment, respectively. Melatonin applied at these time points increased the contraction by 20 +/- 5, 41 +/- 10, and 48 +/- 8%, respectively, relative to control. This increase in potentiating effect of melatonin during the course of experiment was not because of sensitization of the segment to the hormone. Acidosis-induced considerable decline in neurogenic contraction was counteracted by melatonin, while after alkalosis-induced augmentation in the contraction the hormone was not effective. Melatonin increased the artery response to 0.1 mum noradrenaline. CONCLUSION These data suggest that melatonin can restore an attenuated neurogenic reactivity of the juvenile rat tail artery. The effect is more pronounced with further decrease in reactivity and might be due to a change in sensitivity of the post-junctional membrane to noradrenaline.
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Affiliation(s)
- O V Karachentseva
- Laboratory of Circulation, Pavlov Institute of Physiology, St Petersburg, Russia
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34
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Dubocovich ML, Markowska M. Functional MT1 and MT2 melatonin receptors in mammals. Endocrine 2005; 27:101-10. [PMID: 16217123 DOI: 10.1385/endo:27:2:101] [Citation(s) in RCA: 590] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2005] [Accepted: 06/13/2005] [Indexed: 11/11/2022]
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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Semerciöz A, Onur R, Ayar A, Orhan I. The inhibitory role of melatonin on isolated guinea-pig urinary bladder: an endogenous hormone effect. BJU Int 2005; 94:1373-6. [PMID: 15610123 DOI: 10.1111/j.1464-410x.2004.05175.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To investigate the effects of melatonin, an endogenous hormone, on acetylcholine and KCl-induced contractions of isolated guinea-pig detrusor muscle. MATERIALS AND METHODS Detrusor smooth muscle strips isolated from guinea-pig bladders were placed in an organ bath containing physiological saline at 37 degrees C and pH 7.4, constantly bubbled with 95% oxygen and 5% CO2. The effects of cumulatively applied melatonin on the acetylcholine- and KCl-induced contractions of isolated bladder strips were examined using isometric contraction measurements. RESULTS Melatonin (100 and 300 micromol/L) significantly inhibited the peak amplitude of both acetylcholine (10 micromol/L) and KCl (30 mmol/L)-induced contraction of the isolated bladder strips (P < 0.05). Similarly, melatonin caused a significant reduction in the contractile frequency induced by KCl (eight strips) in a concentration-dependent manner, while having no significant effect on the frequency of contractile response to acetylcholine, even at the highest concentration (300 micromol/L) used (P = 0.58, 14 strips). CONCLUSIONS These results suggest that melatonin inhibits acetylcholine- and KCl-induced contractions in isolated bladder strips from guinea pigs. The endogenous nature of melatonin, with its low side-effect profile, makes it a potentially useful agent to be considered in the medical management of the overactive bladder.
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Affiliation(s)
- Atilla Semerciöz
- Department of Urology, Abant Izzet Baysal University, Izzet Baysal Medical Faculty, Elazig, Turkey
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36
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Satoh H, Nishida S. Electropharmacological actions of Ginkgo biloba extract on vascular smooth and heart muscles. Clin Chim Acta 2005; 342:13-22. [PMID: 15026263 DOI: 10.1016/j.cccn.2003.12.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2003] [Revised: 12/11/2003] [Accepted: 12/11/2003] [Indexed: 11/26/2022]
Abstract
Ginkgo biloba extract (GBE) is composed mostly of two constituents: One is terpenoids (such as bilobalide, ginkgolides A, B and C), and the other is flavonoids (such as quercetin and rutin). After oral administration of GBE (160 mg) to healthy volunteers, the plasma concentrations of ginkgolides A and B and bilobalide are 41.8, 5.6 and 37.6 ng/ml, respectively. GBE and bilobalide cause a potent concentration-dependent relaxation. NG-Monomethyl-l-arginine acetate (l-NMMA), an NO synthesis inhibitor, reduces the vasodilation induced by GBE. Furthermore, the vasorelaxation of GBE is attenuated in Ca2+-free medium. Bilobalide possesses similar mechanisms. The other constituents also produce vasorelaxation. On the other hand, all the compounds markedly modify the action potential configuration in guinea pig ventricular cardiomyocytes. GBE prolongs the action potential duration (APD), whereas bilobalide shortens the APD. In patch-clamp experiments, GBE markedly inhibits the Ca2+ current (ICa), the delayed rectifier K+ current (IK) and the inwardly rectifying K+ current (IK1). On the contrary bilobalide enhances the ICa and IK currents concentration-dependently. The other constituents do not cause their actions in a uniform direction. In the rat sino-atrial (SA) node, GBE causes a negative chronotropic effect. These results indicate that GBE and the constituents produce effective electropharmacological actions in the cardiomyocytes and cause vasodilation, mainly due to the inhibitions of Ca2+ influx through the Ca2+ channel and the activation of NO release in the endothelium and aortic vascular muscles.
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Affiliation(s)
- Hiroyasu Satoh
- Department of Pharmacology, Division of Crude and Herbal Medicine, Nara Medical University, Kashihara, Nara 634-8521, Japan.
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37
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Kadekaro AL, Andrade LNS, Floeter-Winter LM, Rollag MD, Virador V, Vieira W, Castrucci AMDL. MT-1 melatonin receptor expression increases the antiproliferative effect of melatonin on S-91 murine melanoma cells. J Pineal Res 2004; 36:204-11. [PMID: 15009512 DOI: 10.1111/j.1600-079x.2004.00119.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Melatonin, a derivative of tryptophan that is present in all vertebrates, was first described in bovine pineal gland. It is known that melatonin is a highly conserved molecule, present also in unicellular organisms and plants. Several effects of melatonin have been described, including receptor- and non-receptor-mediated actions. Herein, we studied the effects of melatonin on in vitro and in vivo cell proliferation of Cloudman S-91 murine melanoma cells. We demonstrated that melatonin treatment significantly inhibits S-91 melanoma cell proliferation in vitro (EC50 = 10-7 m) as well as reduces tumor growth in vivo. We also demonstrated that melatonin directly increases the activity of the antioxidant enzymes catalase and glutathione peroxidase. These effects are most likely triggered through the direct intracellular action of melatonin, since the presence of receptors could not be demonstrated in this cell line. Expression of MT-1 melatonin receptor by stable transfection, mediated a dramatic antiproliferative melatonin effect (EC50 = 10-10 m) in S-91 cells. The expressed receptor is negatively coupled to the adenylyl cyclase/cyclic AMP signaling pathway via Gi protein. These results suggest that expression of the MT-1 melatonin receptor in melanoma cells is a potential alternative approach to specifically target cells in cancer therapeutic treatment.
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MESH Headings
- Animals
- Antineoplastic Agents/pharmacology
- Binding Sites
- Catalase/drug effects
- Catalase/metabolism
- Cell Division/drug effects
- Colforsin/pharmacology
- Cyclic AMP/metabolism
- Dose-Response Relationship, Drug
- GTP-Binding Protein alpha Subunits, Gi-Go/drug effects
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Glutathione Peroxidase/drug effects
- Glutathione Peroxidase/metabolism
- Male
- Melanoma/drug therapy
- Melanoma/metabolism
- Melanoma/pathology
- Melatonin/pharmacology
- Mice
- Mice, Inbred DBA
- Receptor, Melatonin, MT1/drug effects
- Receptor, Melatonin, MT1/genetics
- Receptor, Melatonin, MT1/metabolism
- Signal Transduction
- Transfection
- Tumor Cells, Cultured
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Affiliation(s)
- Ana Luisa Kadekaro
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brasil.
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38
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Karachentseva OV, Yartsev VN, Dvoretsky DP. Melatonin restores diminished neurogenic reactivity of the juvenile rat tail artery. ACTA PHYSIOLOGICA HUNGARICA 2004; 91:197-203. [PMID: 16438113 DOI: 10.1556/aphysiol.91.2004.3-4.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The effect of melatonin on neurogenic reactivity of the juvenile rat tail artery segment was studied. The electrical field stimulation-evoked contraction of the segment decreased in the course of the experiment. Melatonin (0.1 microM) applied at different time points of the experiment produced an increase in the contraction, which directly correlated with a spontaneous decrease in the electrical field stimulation-evoked response. The increase in the potentiating effect of melatonin in the course of the experiment was not due to sensitization of the segment to this substance. Noradrenaline-evoked contraction of the vessel segment was not changed by melatonin. The data indicate that melatonin restores the diminished neurogenic reactivity of the juvenile rat tail artery probably by potentiation of the contractile response of the vessel, but this effect is hardly due to a change in sensitivity of the postjunctional membrane to noradrenaline.
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Affiliation(s)
- O V Karachentseva
- Laboratory of Circulation, Pavlov Institute of Physiology, St Petersburg, Russia
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39
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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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40
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O'Rourke ST, Hammad H, Delagrange P, Scalbert E, Vanhoutte PM. Melatonin inhibits nitrate tolerance in isolated coronary arteries. Br J Pharmacol 2003; 139:1326-32. [PMID: 12890712 PMCID: PMC1573966 DOI: 10.1038/sj.bjp.0705383] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2003] [Revised: 03/28/2003] [Accepted: 05/13/2003] [Indexed: 11/09/2022] Open
Abstract
(1) The present study was designed to test the hypothesis that melatonin inhibits nitrate tolerance in coronary arteries. (2) Rings of porcine coronary arteries were suspended in organ chambers for isometric tension recording. Nitrate tolerance was induced by incubating the tissues with nitroglycerin (10(-4) M) for 90 min, followed by repeated rinsing for 1 h. Control rings that had not been exposed previously to nitroglycerin, but were otherwise treated identically, were studied simultaneously. The rings were contracted with U46619 (1-3 x 10(-9) M) and concentration-response curves to nitroglycerin (10(-9)-10(-4) M) were obtained. (3) Nitrate tolerance was evident by a 15- to 20-fold rightward shift in the concentration-response curve to nitroglycerin in rings with and without endothelium exposed previously to the drug for 90 min. Addition of melatonin (10(-9)-10(-7) M) to the organ chamber during the 90-min incubation period with nitroglycerin partially inhibited nitrate tolerance in coronary arteries with intact endothelium; however, melatonin had no effect on nitrate tolerance in coronary arteries without endothelium. (4) The effect of melatonin on nitrate tolerance in coronary arteries with endothelium was abolished by the melatonin receptor antagonist, S20928 (10(-6) M). In contrast to melatonin, the selective MT(3)-melatonin receptor agonist, 5-MCA-NAT (10(-8)-10(-7) M), had no effect on nitrate tolerance in coronary arteries. (5) The results demonstrate that melatonin, acting via specific melatonin receptors, inhibits nitrate tolerance in coronary arteries and that this effect is dependent on the presence of the vascular endothelium.
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MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/antagonists & inhibitors
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Animals
- Arteries
- Coronary Vessels/drug effects
- Coronary Vessels/physiology
- Cromakalim/pharmacology
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/surgery
- In Vitro Techniques
- Isometric Contraction/drug effects
- Isometric Contraction/physiology
- Isoproterenol/pharmacology
- Melatonin/pharmacology
- Melatonin/physiology
- Muscle, Smooth, Vascular/drug effects
- Naphthalenes/pharmacology
- Nitrates/administration & dosage
- Nitrates/adverse effects
- Nitrates/pharmacokinetics
- Nitroglycerin/adverse effects
- Nitroglycerin/pharmacology
- Receptors, Melatonin/antagonists & inhibitors
- Receptors, Melatonin/drug effects
- Swine
- Tachyphylaxis/physiology
- Time Factors
- Tryptamines/pharmacology
- Vasoconstriction/drug effects
- Vasodilation/drug effects
- Vasodilator Agents/pharmacology
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Affiliation(s)
- Stephen T O'Rourke
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND 58105, USA.
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41
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Nishida S, Satoh H. Mechanisms for the vasodilations induced by Ginkgo biloba extract and its main constituent, bilobalide, in rat aorta. Life Sci 2003; 72:2659-67. [PMID: 12672511 DOI: 10.1016/s0024-3205(03)00177-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Vasodilating actions of Ginkgo biloba extract (GBE) and bilobalide, a main constituent, were examined using rat aorta ring strips. GBE at the concentration ranges from 0.03 to 3 mg/ml had a potent concentration-dependent relaxation, reaching 70 +/- 4.5% (n = 6, P < 0.001) at 3 mg/ml. Bilobalide at 0.1 to 100 microM also caused the relaxation in a concentration-dependent manner. At 100 microM, bilobalide caused dilation by 17.6 +/- 3.9% (n = 7, P < 0.05). NG-monomethyl-L-arginine acetate (L-NMMA)(100 microM), an NO synthesis inhibitor, reduced the vasodilation of GBE (3 mg/ml) to 57.6 +/- 2.5% (n = 6, P < 0.05), and was accompanied with a decrease in the rate of relaxation. Tetraethylammonium (TEA)(100 microM), a Ca(2+)-activated K(+) channel inhibitor, also decreased the GBE (3 mg/ml)-induced relaxation to 63.1 +/- 4.6% (n = 6), but not significantly. Indomethacin tended to reduce the GBE (3 mg/ml)-induced vasorelaxation to 67.3 +/- 4.1% (n = 6). In contrast, the vasorelaxation of GBE (3 mg/ml) was strongly attenuated to 53 +/- 6.1% (n = 7, P < 0.05) in Ca(2+)-free medium. Similarly, the vasorelaxation induced by bilobalide significantly decreased both by pretreatment with NO inhibitor (L-NMMA) and in Ca(2+)-free solution. These results indicate that the relaxation induced by GBE would be due to the inhibition of Ca(2+) influx through the Ca(2+) channel and the activation of NO release, and might be in part due to the inhibitions of Ca(2+)-activated K(+) current and PGI(2) release, in the endothelium and aortic vascular muscles. Bilobalide possesses the similar mechanisms for the vasodilation.
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Affiliation(s)
- Seiichiro Nishida
- Department of Pharmacology, Division of Crude and Herbal Medicine, Nara Medical University, Kashihara, Nara 634-8521, Japan
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42
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Witt-Enderby PA, Bennett J, Jarzynka MJ, Firestine S, Melan MA. Melatonin receptors and their regulation: biochemical and structural mechanisms. Life Sci 2003; 72:2183-98. [PMID: 12628439 DOI: 10.1016/s0024-3205(03)00098-5] [Citation(s) in RCA: 201] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is growing evidence demonstrating the complexity of melatonin's role in modulating a diverse number of physiological processes. This complexity could be attributed to the fact that melatonin receptors belong to two distinct classes of proteins, that is, the G-protein coupled receptor superfamily (MT(1), MT(2)) and the quinone reductase enzyme family (MT(3)) which makes them unique at the molecular level. Also, within the G-protein coupled receptor family of proteins, the MT(1) and MT(2) receptors can couple to multiple and distinct signal transduction cascades whose activation can lead to unique cellular responses. Also, throughout the 24-hour cycle, the receptors' sensitivity to specific cues fluctuates and this sensitivity can be modulated in a homologous fashion, that is, by melatonin itself, and in a heterologous manner, that is, by other cues including the photoperiod or estrogen. This sensitivity of response may reflect changes in melatonin receptor density that also occurs throughout the 24-hour light/dark cycle but out of phase with circulating melatonin levels. The mechanisms that underlie the changes in melatonin receptor density and function are still not well-understood, but data is beginning to show that transcriptional events and G-protein uncoupling may be involved. Even though this area of research is still in its infancy, great strides are being made everyday in elucidating the mechanisms that underlie melatonin receptor function and regulation. The focus of this review is to highlight some of these discoveries in an attempt to reveal the uniqueness of the melatonin receptor family while at the same time provide thought-provoking ideas to further advance this area of research. Thus, a brief overview of each of the mammalian melatonin receptor subtypes and the signal transduction cascades to which they couple will be discussed with a greater emphasis placed on the mechanisms underlying their regulation and the domains within the receptors essential for proper signaling.
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Affiliation(s)
- Paula A Witt-Enderby
- Division of Pharmaceutical Sciences, Duquesne University School of Pharmacy, 421 Mellon Hall, Pittsburgh, PA 15282, USA.
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Masana MI, Doolen S, Ersahin C, Al-Ghoul WM, Duckles SP, Dubocovich ML, Krause DN. MT(2) melatonin receptors are present and functional in rat caudal artery. J Pharmacol Exp Ther 2002; 302:1295-302. [PMID: 12183692 DOI: 10.1124/jpet.302.3.1295] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In rat caudal artery, contraction to melatonin results primarily from activation of MT(1) melatonin receptors; however, the role of MT(2) melatonin receptors in vascular responses is controversial. We examined and compared the expression and function of MT(2) receptors with that of MT(1) receptors in male rat caudal artery. MT(1) and MT(2) melatonin receptor mRNA was amplified by reverse transcription-polymerase chain reaction from caudal arteries of three rat strains (i.e., Fisher, Sprague-Dawley, and Wistar). Antisense (but not sense) (33)P-labeled oligonucleotide probes specific for MT(1) or MT(2) receptor mRNA hybridized to smooth muscle, as well as intimal and adventitial layers, of caudal artery. In male Fisher rat caudal artery denuded of endothelium, melatonin was 10 times more potent than 6-chloromelatonin to potentiate contraction to phenylephrine, suggesting activation of smooth muscle MT(1) melatonin receptors. The MT(1)/MT(2) competitive melatonin receptor antagonist luzindole (3 microM), blocked melatonin-mediated contraction (0.1-100 nM) with an affinity constant (K(B) value of 157 nM) similar to that for the human MT(1) receptor. However, at melatonin concentrations above 100 nM, luzindole potentiated the contractile response, suggesting blockade of MT(2) receptors mediating vasorelaxation and/or an inverse agonist effect at MT(1) constitutively active receptors. The involvement of MT(2) receptors in vasorelaxation is supported by the finding that the competitive antagonists 4-phenyl 2-acetamidotetraline and 4-phenyl-2-propionamidotetraline, at MT(2)-selective concentrations (10 nM), significantly enhanced contractile responses to all melatonin concentrations tested (0.1 nM-10 microM). We conclude that MT(2) melatonin receptors expressed in vascular smooth muscle mediate vasodilation in contrast to vascular MT(1) receptors mediating vasoconstriction.
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MESH Headings
- Animals
- Arteries/metabolism
- Base Sequence
- In Situ Hybridization
- Male
- Melatonin/metabolism
- Molecular Sequence Data
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/metabolism
- RNA, Messenger/biosynthesis
- Rats
- Rats, Inbred F344
- Rats, Sprague-Dawley
- Rats, Wistar
- Receptors, Cell Surface/biosynthesis
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Cytoplasmic and Nuclear/biosynthesis
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Melatonin
- Reverse Transcriptase Polymerase Chain Reaction
- Species Specificity
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Affiliation(s)
- Monica I Masana
- Department of Molecular Pharmacology and Biological Chemistry, The Feinberg School of Medicine, Northwestern University, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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Storr M, Koppitz P, Sibaev A, Saur D, Kurjak M, Franck H, Schusdziarra V, Allescher HD. Melatonin reduces non-adrenergic, non-cholinergic relaxant neurotransmission by inhibition of nitric oxide synthase activity in the gastrointestinal tract of rodents in vitro. J Pineal Res 2002; 33:101-8. [PMID: 12153444 DOI: 10.1034/j.1600-079x.2002.02909.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The aim of the present study was to investigate the effects of melatonin on non-adrenergic, non-cholinergic (NANC) relaxant neurotransmission in the gastrointestinal tract, which is mainly mediated by nitrergic and peptidergic mechanisms. Melatonin (10(-7)-10(-3) M) had no effect on the basal tonus of the rat gastric fundus smooth muscle. Relaxant responses following electrical stimulation(40 V; 0.5 ms pulse duration; 10 s stimulation duration) under NANC conditions on a 5-hydroxytryptamine (5-HT, 10(-7) M) contraction plateau were elicited at frequencies in the range of 0.5-16 Hz. Melatonin significantly reduced these inhibitory NANC responses (16 Hz without melatonin: -103 +/- 6.3%; melatonin 10(-5) M: -80.4 +/- 7.5%; melatonin 10(-4) M: -39.1 +/- 17.1%). Intracellular recording was carried out in a mouse colonic preparation. Electrical neural stimulation of the mouse colonic neurons caused biphasic intracellular hyperpolarization in smooth-muscle cells. The initial fast component is apamin-sensitive, and the following slow component is dependent on nitrergic mechanisms, as it is abolished in the presence of NG-nitro-L-arginine (L-NNA). Melatonin significantly reduced the nitric oxide-dependent slow component of neurally transmitted hyperpolarization, whereas the initial fast component was left unchanged. In a synaptosomal preparation of the enteric nervous system of rat intestine, enzymatic nitric oxide synthase (NOS) activity was significantly reduced by melatonin at concentrations ranging from 10(-7) to 10(-4) M (basal preparation including cofactors: 61.2 +/- 9.4 fmol/mg; melatonin 10(-4) M: 39.2 +/- 6.9 fmol/mg). Reverse transcriptase-polymerase chain reaction (RT-PCR) studies were conducted to investigate the melatonin receptors (mt(1), MT(2) and MT(3)) present in the esophagus, stomach and ileum of the rat. The presence of mt1 mRNA expression alone, but not of mRNA expression for MT(2) or MT(3), was demonstrated in the tissues. In conclusion, this study demonstrates that melatonin reduces the functional inhibitory NANC response. It shows that this effect may be the result of a reduction of the nitrergic component of the smooth-muscle inhibitory junction potential (IJP) and related to direct inhibition of NOS activity in enteric synaptosomes. The presence of mt1 receptor transcripts adds supportive evidence for a possible physiological role of melatonin within the enteric nervous system.
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MESH Headings
- Adrenergic Agents/pharmacology
- Animals
- Atropine/pharmacology
- Digestive System/enzymology
- Digestive System/physiopathology
- Electric Stimulation
- Enteric Nervous System/drug effects
- Enteric Nervous System/metabolism
- Enzyme Inhibitors/pharmacology
- Female
- In Vitro Techniques
- Male
- Melatonin/pharmacology
- Melatonin/physiology
- Membrane Potentials/drug effects
- Metallothionein 3
- Mice
- Mice, Inbred BALB C
- Muscarinic Antagonists/pharmacology
- Muscle Relaxation/drug effects
- Muscle, Smooth/drug effects
- Neurotransmitter Agents/metabolism
- Nitric Oxide Synthase/antagonists & inhibitors
- Rats
- Rats, Wistar
- Receptors, Cell Surface/drug effects
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Cytoplasmic and Nuclear/drug effects
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Melatonin
- Rodentia
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Synaptosomes/drug effects
- Synaptosomes/metabolism
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Affiliation(s)
- M Storr
- Department of Internal Medicine II, Technical University of Munich, Munich, Germany.
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Poon AMS, Kravtsov GM, Pang SF. Receptor-mediated modulation of avian caecal muscle contraction by melatonin: role of tyrosine protein kinase. J Pineal Res 2002; 32:199-208. [PMID: 12074105 DOI: 10.1034/j.1600-079x.2002.1o857.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract: Melatonin receptors in the quail caecum were studied by 2[125I]iodomelatonin binding assay and the involvement of tyrosine protein kinase in the melatonin-induced contraction was explored. The binding of 2[125I]iodomelatonin in the quail caecum membrane preparations was saturable, reversible and of high affinity with an equilibrium dissociation constant (Kd) of 24.6 +/- 1.1 pm (n = 7) and a maximum number of binding sites (Bmax) of 1.95 +/- 0.09 fmol (mg/protein) (n = 7). The relative order of potency of indoles in competing for 2[125I]iodomelatonin binding was: 2-iodomelatonin > melatonin > 2-phenylmelatonin > 6-chloromelatonin > 6-hydroxymelatonin > N-acetylserotonin, indicating that ML(1) receptors are involved. The binding was inhibited by Mel1b melatonin receptor antagonists, luzindole and 4-phenyl-2-propionamidotetralin (4-P-PDOT) as well as by non-hydrolyzable analogs of GTP like GTPgammaS and Gpp(NH)p but not by adenosine nucleotides. The latter suggests that the action of melatonin on the caecum is G-protein linked. Cumulative addition of melatonin (1-300 nM) potentiated both the amplitude and frequency of spontaneous contractions in the quail caecum. The potentiation of rhythmic contractions was blocked by both luzindole and 4-P-PDOT. Antagonists of tyrosine kinase, genistein(2 microM) and erbstatin(4 microM) suppressed the modulation of spontaneous contractions by melatonin, but not inhibitors of protein kinase C (PKC) or protein kinase A (PKA). Melatonin-induced increment in spontaneous contraction was blocked by nifedipine (0.4 nM). Thus, we suggest that melatonin potentiates spontaneous contraction in the quail caecum via interacting with G-protein-coupled Mel(1b) receptor which may activate L-type Ca2+ channels by mobilizing tyrosine kinases.
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MESH Headings
- 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine/pharmacology
- Animals
- Apamin/pharmacology
- Binding, Competitive
- Cecum/drug effects
- Cecum/metabolism
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology
- Guanosine Triphosphate/metabolism
- Guanosine Triphosphate/pharmacology
- Indoles/metabolism
- Melatonin/analogs & derivatives
- Melatonin/metabolism
- Melatonin/pharmacology
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Naphthalenes/pharmacology
- Potassium Channels/drug effects
- Potassium Channels/metabolism
- Protein-Tyrosine Kinases/metabolism
- Quail
- Receptors, Cell Surface/antagonists & inhibitors
- Receptors, Cell Surface/drug effects
- Receptors, Cell Surface/metabolism
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Receptors, Cytoplasmic and Nuclear/drug effects
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Melatonin
- Tetrahydronaphthalenes/pharmacology
- Tryptamines/pharmacology
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Affiliation(s)
- A M S Poon
- Department of Physiology, Faculty of Medicine, The University of Hong Kong, China.
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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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Lotufo CM, Lopes C, Dubocovich ML, Farsky SH, Markus RP. Melatonin and N-acetylserotonin inhibit leukocyte rolling and adhesion to rat microcirculation. Eur J Pharmacol 2001; 430:351-7. [PMID: 11711054 DOI: 10.1016/s0014-2999(01)01369-3] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The hormone melatonin produced by the pineal gland during the daily dark phase regulates a variety of biological processes in mammals. The aim of this study was to determine the effect of melatonin and its precursor N-acetylserotonin on the microcirculation during acute inflammation. Arteriolar diameter, blood flow rate, leukocyte rolling and adhesion were measured in the rat microcirculation in situ by intravital microscopy. Melatonin alone or together with noradrenaline did not affect the arteriolar diameter or blood flow rate. Melatonin inhibited both leukocyte rolling and leukotriene B(4) induced adhesion while its precursor N-acetylserotonin inhibits only leukocyte adhesion. The rank order of potency of agonists and antagonist receptor selective ligands suggested that the activation of MT(2) and MT(3) melatonin binding sites receptors modulate leukocyte rolling and adhesion, respectively. The effect of melatonin and N-acetylserotonin herein described were observed with concentrations in the range of the nocturnal surge, providing the first evidence for a possible physiological role of these hormones in acute inflammation.
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Affiliation(s)
- C M Lotufo
- Department of Physiology, Institute of Bioscience, University of São Paulo, São Paulo, Brazil
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Girouard H, Chulak C, Lejossec M, Lamontagne D, de Champlain J. Vasorelaxant effects of the chronic treatment with melatonin on mesenteric artery and aorta of spontaneously hypertensive rats. J Hypertens 2001; 19:1369-77. [PMID: 11518844 DOI: 10.1097/00004872-200108000-00004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To investigate the effect of a chronic treatment with melatonin on arterial pressure and a possible improvement of the vascular muscarinic and NO synthase (NOS) pathways in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. DESIGN AND METHODS Mean arterial pressure (MAP), systolic (SBP), diastolic blood pressure (DBP), and heart rate (HR) were evaluated in conscious rats treated with 30 mg/kg per day of melatonin during 4 weeks. Changes in MAP were evaluated following an intravenous injection of the NOS inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME). Relaxant effects of acetylcholine (Ach), sodium nitroprusside (SNP), and the calcium ionophore A23187 were examined on mesenteric beds and aortic rings with or without treatment with melatonin. RESULTS Melatonin produced a significant reduction of MAP, SBP, DBP and HR in SHR (P < 0.05). L-NAME increased the MAP of melatonin-treated SHR by the same magnitude as that of WKY rats which was significantly higher than that of non-treated SHR (P< 0.05). Melatonin treatment improved the maximal relaxation of mesenteric arteries to A23187 in SHR (P < 0.001) to the WKY level and caused a slight increment in Ach- and A23187-induced vasodilations in aorta from SHR and WKY rats (P < 0.05). CONCLUSION The present study showed that melatonin exerted a bradycardic and an antihypertensive action in SHR. The enhancement by melatonin of the endothelium-dependent vasodilation (Ach and/or A23187) in mesenteric artery and aorta from SHR and WKY rats and the higher increase in MAP following L-NAME treatment in melatonin-treated SHR suggest the contribution of an improved vascular NOS pathway activity in the hypotensive effect of melatonin.
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Affiliation(s)
- H Girouard
- Department of Physiology, Faculty of Medicine, University of Montréal, Succursale Centreville, Québec, Canada
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Tom B, De Vries P, Heiligers JP, Willems EW, Scalbert E, Delagrange P, Saxena PR. The lack of vasoconstrictor effect of the pineal hormone melatonin in an animal model predictive of antimigraine activity. Cephalalgia 2001; 21:656-63. [PMID: 11531897 DOI: 10.1046/j.1468-2982.2001.00215.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pineal hormone, melatonin, has been implicated in the pathophysiology of migraine and several studies have demonstrated its vasoconstrictor properties. In the present study, systemic and carotid haemodynamic effects of melatonin, administered directly into the carotid artery, were investigated in anaesthetized pigs. Ten-minute intracarotid infusions of melatonin (1, 10 and 100 microg kg(-1) min(-1)) produced slight decreases in blood pressure and total carotid and arteriovenous anastomotic blood flows, but nutrient blood flow was not affected. The decrease in carotid blood flow was entirely caused by the hypotension, since no changes in vascular conductance values were observed. It is concluded that melatonin itself is not capable of producing vasoconstriction in the cranial circulation of anaesthetized pigs. Thus, it appears that melatonin has no anti-migraine potential via a vasoconstrictor mechanism.
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Affiliation(s)
- B Tom
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
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Li Z, Nakaya Y, Niwa Y, Chen X. K(Ca) channel-opening activity of Ginkgo Biloba extracts and ginsenosides in cultured endothelial cells. Clin Exp Pharmacol Physiol 2001; 28:441-5. [PMID: 11380519 DOI: 10.1046/j.1440-1681.2001.03456.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Extracts of Ginkgo biloba (EGb) and ginsenosides (GS) have been reported to induce vasorelaxation. In the present study, the role of K+ channels in the action of EGb and GS to activate nitric oxide synthase (NOS) activity was investigated in cultured endothelial cells. 2. Nitric oxide synthase activity of cultured endothelial cells detected by the reduced nicotinamide adenine dinucleotide phosphate (NADPH) histochemistry method was significantly increased after treatment with 20 microg/mL EGb or 40 microg/mL GS plus 10 mmol/L L-arginine. The effect was completely abolished by the addition of 0.5 micromol/L Nomega-nitro-L-arginine, an inhibitor of NOS, to the incubation medium and partially inhibited by 10 micromol/L tetraethylammonium (TEA), an inhibitor of Ca2+-activated K+ (KCa) channels. 3. Application of EGb to the intracellular surface of excised inside-out patches activated K+ channels in a concentration-dependent manner in the concentration range 1-100 microg/mL. Channel activity was also activated by application of GS at concentrations ranging from 1 to 300 microg/mL. The modulation of channel activity was inhibited by 0.5 mmol/L TEA but not by 0.5 mmol/L glibenclamide, an inhibitor of ATP-sensitive K+ channels. 4. Thus, in cultured endothelial cells, the increase in NOS activity induced by EGb or GS depends on the activity of KCa channels. These compounds may regulate nitric oxide release by changing the cell membrane potential in vascular endothelial cells.
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Affiliation(s)
- Z Li
- Department of Pharmacology, Hunan Medical University, Changsha, China
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