IntechOpen

Home > Books > Melatonin - Molecular Biology, Clinical and Pharmaceutical Approaches

Open access peer-reviewed chapter

How Can Molecular Pharmacology Help Understand the Multiple Actions of Melatonin: 20 Years of Research and Trends

Written By

Jean A. Boutin

Submitted: 13 February 2018 Reviewed: 14 June 2018 Published: 21 November 2018

DOI: 10.5772/intechopen.79524

Melatonin IntechOpen
Melatonin Molecular Biology, Clinical and Pharmaceutica... Edited by Cristina Manuela Dragoi

From the Edited Volume

Melatonin - Molecular Biology, Clinical and Pharmaceutical Approaches

Edited by Cristina Manuela Drăgoi and Alina Crenguţa Nicolae

Book Details Order Print

Chapter metrics overview

1,331 Chapter Downloads

View Full Metrics
Advertisement

Abstract

Melatonin actions are so numerous that a naive reader might become suspicious at such wonders. In a systematic way, we would like to summarize the various approaches that led to what is scientifically sounded in terms of molecular pharmacology: where and how melatonin is acting as a molecule, what can be its action as an antioxidant per se, and its side effects at a molecular level not as a drug or in vivo. Finally, the nature of the relationship between melatonin and mitochondria should be decrypted as well. The road we took from 1987 up to now, and particularly after 1995, will be mentioned with special considerations to the receptors from various species and our goals beyond that; the synthesis and catabolism of melatonin and their link to other enzymes; the discovery of the MT3 binding sites, and what’s left to understand on this particularly interesting target; and the search for agonists that occulted part of the potential discovery of true and potent antagonists, a situation quite unique among the G-protein-coupled receptors.

Keywords

  • melatonin
  • molecular pharmacology
  • MT1
  • MT2
  • catabolism

1. Introduction

Melatonin is a neurohormone synthesized by the pineal gland at night. The longer the night, the higher the concentration of melatonin in the blood. Even if new information is modulating this basic principle, this rhythmicity has been the basis of many published observations linking melatonin to many physiological features of animals, including human. This comprises the daily changes in light and the way the body understands the successions of dark and clear periods but also the circannual rhythmicity, during which animals prepare for the harsher winter period during which access to food is more difficult. By “measuring” the length of melatonin synthesis periods (directly proportional to the length of the nights), animals start to modify their physiology in order to prepare the time to come: accumulation of fat (fat storing) for some, food storing for others, and preparing the bodies to reproduction for all animals at the best period to avoid the exposure of the newborns to cold and difficult conditions. Apparently, humans have lost this advanced capacity in our ever lit-up society.

New evidences recently caught our attention and challenge our ways of understanding the melatonin actions and pathways, whether because it seems that light can be “seen” by the body without the relay of melatonin or because one finds that melatonin is synthesized in mitochondria in all parts of the brain, as opposed to the pivotal and ancient statement: melatonin is synthesized by the pineal gland only. Nowadays, one can also see many publications claiming that melatonin helps cure cancer as well as so many other diseases (see a non-exhaustive selection of such actions since 2015 in Table 1). All these information should be treated with respect, integrated inside our decade-old knowledge and carefully evaluated as a contribution to a bigger picture. The basics on melatonin can be found in some recent reviews [1, 2, 3, 4, 5]. The present chapter concentrates on the molecular pharmacology of melatonin. This small molecule, derived from tryptophan, has a limited number of recognized targets. It is synthesized and catabolized by a limited and well-known number of enzymes that have been described in the past (see Figure 1 for a simplistic summary). The core of the discussion seems always to be the same: how this molecule can be active on so many pathological events? How antioxidant this molecule is and why? What makes it so special? Some of these points are reviewed in the present chapter based on two decades of research in this area.

Authors Date Protection against Targets Amount Species Ref
Abdel-Moneim et al. 2015 Naja naja venom toxicity — 10 mg/kg Rat [100]
Allagui et al. 2015 Aluminum-induced toxicity / 10 mg/kg Rat [101]
Al-Olayan et al. 2015 Aluminum-induced injury Neurons 10 mg/kg Rat [102]
Al-Rasheed et al. 2016 CCl4-induced toxicity Liver 20 mg/kg Rat [103]
Amin et al. 2015 Diabetes-induced apoptosis Heart 10 mg/kg Rat [104]
Asghari et al. 2017 Aluminum phosphide toxicity Heart 20–50 mg/kg Rat [105]
Banaei et al. 2016 Ischemia–reperfusion injury Kidney 10 mg/kg Rat [106]
Barberino et al. 2017 Cisplatin-induceddamage Ovaries 5–20 mg/kg Mouse [107]
Berkiks et al. 2017 Ccognitive disorders Brain 5 mg/kg Rat [108]
Cao et al. 2017 Subarachnoid hemorrhage Brain 150 mg/kg Rat [109]
Cebi et al. 2018 Radioiodine treatment Testicles 12 mg/kg/day Rat [110]
Chang et al. 2016 Ischemia–reperfusion injury Kidney 90 mg Rat [111]
Chang et al. 2015 Ischemia/reperfusion injury Adipose stem cells 120 mg/kg Rat [112]
Chen et al. 2016 Endoplasmic reticulum stress Pancreas 0.5–2 mM Rat [113]
Chen et al. 2017 Neuropathic pain / ??? Rat [114]
Czechowska et al. 2015 Thioacetamide-induced fibrosis Liver 10 mg/kg Rat [115]
Das et al. 2017 Mitochondrial dysfunction Hepatocytes 10–20 mg/kg/day Mouse [116]
Ding et al. 2018 Post-traumtic cardiac function Heart 100 μM Rat [117]
Ding et al. 2015 Traumatic injury-induced apoptosis Brain 10 mg/kg Mouse [118]
Dos Santos et al. 2018 Lupus nephritis injury Kidney 10 mg/kg/day Mouse [119]
Drag-Kozak et al. 2018 Cadmium-induced toxicity Reproductive organ 4 mg/L Carp [120]
Ewida et al. 2016 Metabolic syndroma Kidney 5 mg/kg Rat [121]
Favero et al. 2017 Fibromyalgia-related alterations Muscle 2.5–5 mg/kg Rat [122]
Fernandez-Gil et al. 2017 Radiotherapy-iondued toxicity Intestine 45 mg/day Rat [123]
Galley et al. 2017 Paclitaxel-induced dysfunction Mitochondria 5–50 mg/kg Rat [124]
Ghaznavi et al. 2016 Gentamicin-induced toxicity Kidney 15 mg/kg/day Rat [125]
Ghosh et al. 2017 Copper ascorbate-induced damage Heart mitochondria 1 μM Goat [126]
Goc et al. 2017 Sodium nitroprusside toxicity Organs 10 mg/kg Mouse [127]
Goudarzi et al. 2017 Cyclophophamide-induced stress Kidneys 5–20 mg/kg Mouse [128]
Hermoso et al. 2016 Steatosis Liver 10 mg/kg Rat [129]
Hsu et al. 2017 Trauma-induced hemorrhage Liver 2 mg/kg Rat [130]
Hu et al. 2017 BBB damage BBB 15 mg/kg Rat [131]
Ji et al. 2017 Sepsis-associated encephalopathy Brain 10 mg/kg Mouse [132]
Jiang et al. 2016 Diabetic-induced inflammation Retina 10 mg/kg/day Rat [133]
Jin et al. 2016 Non-alcoholic fatty liver disease Liver / Mouse [134]
Karaer et al. 2015 Radiation damage Inner ear 5 mg/kg Rat [135]
Karimfar et al. 2015 Cryopreservation stress Sperm 0.001–1 mM Human [136]
Khaksar et al. 2017 Fluoxetine-induced tissue injury Organs 1 mg/kg Rat [137]
Khalil et al. 2015 Zonisamide-induced toxicity / 10 mg/kg Rat [138]
Koc et al. 2016 Apoptosis Olfactive neurons 10 mg/kg/day Rat [139]
Lebda et al. 2018 Thioacetamide-induced fibrosis Liver 5 mg/kg/day Rat [140]
Lee et al. 2016 H2O2-mediated cell death Keratinocytes 2.5–10 μM Human [141]
Li et al. 2016 Cadmium-induced toxicity Testicles 1 mg Mouse [142]
Li et al. 2015 Maturation defect Oocyte 0.001–1 μM Pig [143]
Lopez et al. 2017 MPTP-toxicity Brain 10 mg/kg Mouse [144]
Lv et al. 2018 Cr(VI) toxicity Testicles 25 mg/kg Mouse [145]
Ma et al. 2018 Oxidative injury Heart 100 μM Rat [146]
Ma et al. 2017 Tripterygium glycosides toxicity Ovaries 20 mg/kg/day Mouse [147]
Ma et al. 2015 Adriamicyn-toxicity Breast cancer cells 10 mg/kg/day Rat [148]
Mehrzadi et al. 2016 Gentamicin-induced toxicity Kidney 20 mg/kg/day Rat [149]
Mirhoseini et al. 2017 Torsion/detorsion model Testicles 25 μg/kg Rat [150]
Montasser et al. 2017 Methotrexate-induced toxicity Liver 10 mg/kg Rat [151]
Mukherjee et al. 2015 Isoproterenol-induced damage Heart mitochondria 0.125–4 μM Goat [152]
Munoz et al. 2017 Cumene peroxide-induced stress Pineal gland 10 mg/kg/day Rat [153]
Naseri et al. 2017 Irradiation-induced toxicity Brain 100 mg/kg Rat [154]
Naskar et al. 2015 MPTP-induced Parkinsonism Brain 10–30 mg/kg Mouse [155]
O’Neal-Moffitt et al. 2015 Alzheimer neiuropathology / Ad libitum??? Mouse [156]
Ortiz et al. 2015 Radiation-induced mucositis Mouth 45 mg/kg/day Rat [157]
Othman et al. 2016 Bisphenopl A-induced toxicity Testicles 10 mg/kg Rat [158]
Ozsoy et al. 2016 Mitochondrial dysfunction Liver 10 mg/kg Rat [159]
Ozsoy et al. 2015 6-hydroxydopamine stress Neurons 10 mg/kg Rat [160]
Pal et al. 2016 Stress-induced behavior changes / 10–100 mg/kg Rat [161]
Pang et al. 2016 Frozen–thawed cycles Sperm 0.01–1 mM Bovine [162]
Patino et al. 2016 o2 & Glucose deprivation Brain slices 10–30 μM Rat [163]
Paul et al. 2018 Oxidative stress Substancia nigra 10–30 mg/kg Rat [164]
Rajput et al. 2017 Alcohol-induced stress Brain 20 mg/kg Mouse [165]
Sadek and Khattab 2017 Arginine-induced pancreatis Pancreas 50 mg/kg Rat [166]
Sarihan et al. 2015 TCDD-induced injury Heart 5 mg/kg/day Rat [167]
Scheuer et al. 2016 UVR-induced erythrema Skin 0.5–12.5% Human [168]
Shahrokhi et al. 2016 Ischmia/reperfusion-oxidative stress Estomac 10 mg/kg Rat [169]
Shang et al. 2016 Colitis-induced neuron damage Colon 2.5 mg/kg/day Rat [170]
Shao et al. 2015 LPS-induced mastitis Breast 5–20 mg/kg Mouse [171]
Shokri et al. 2015 Pilocarpine-induced epilesy Brain 5–20 mg/kg Rat [172]
Shokrzadeh et al. 2015 Cyclophosphamide toxicity Lung 2.5–20 mg/kg Mouse [173]
Sinha et al. 2018 Hypoxy/Ischemy Brain 10 mg/kg Mouse [174]
Tanabe et al. 2015 Oxidative stress ??? 100 μg/kg Mouse [175]
Tang et al. 2017 Abdominal aortic aneurysm Aorta 10 mg/kg/day Rat [176]
Tas et al. 2015 Ischemia/reperfusion injury Intestine 50 mg/kg Rat [177]
Torabi et al. 2017 Cyclophosphamide-induced toxicity Testicles 10 mg/kg/day Rat [178]
Uygur et al. 2016 As-induced apoptosis Testicles 25 mg/kg/day Rat [179]
Vazan et al. 2015 Epinephrine-induced injury Heart 50 μM Rat [180]
Vinod et al. 2016 Aging-induced NO rhythm loss Brain 30 μg/kg/day Rat [181]
Wang et al. 2018 Intracerebral Hemorrahge Brain ??? Rat [182]
Wang et al. 2016 Smoke-induiced vascular injury Blood samples 10 mg/kg Rat [183]
Wang et al. 2016 Smoke-induiced vascular injury Blood samples 3 mg/day Human [183]
Xue et al. 2017 Kainic-induced cell death Brain 20 mg/kg Mouse [184]
Yang et al. 2018 Subarachnoid hemorrhage Brain 0.1–10 μM Mouse [185]
Yi et al. 2017 Stress-induced inflammation Macrophages 50–100 mg/kg Mouse [186]
Yildirim et al. 2016 Ureteral obstruction-induced injury Kidney 10 mg/kg Rat [187]
Yu et al. 2018 Ischemia–reperfusion injury Heart 10 mg/kg Rat [188]
Yu et al. 2018 MEHP-induced meiosis defect Oocytes ??? Pig [189]
Yu et al. 2015 Ischemia/reperfusion injury Heart 10 mg/kg/day Rat [190]
Yu et al. 2015 Ischemia/reperfusion injury Heart 20 mg/kg/day Rat [191]
Zasada et al. 2015 Nitrobenzene-induced peroxidation Thyroids 0.001–10 mM Pig [192]
Zhai et al. 2017 Pathological cardiac hypertrophy Heart 20 mg/kg/day Mouse [193]
Zhang et al. 2017 Bisphenol A-induced toxicity Oocytes 30 mg/kg Mouse [194]
Zhang et al. 2017 Diabetic cardiomyopathy Heart 20 mg/kg/day Mouse [195]
Zhang et al. 2017 Arsenic-induced injury Liver 5–20 mg/kg Rat [196]
Zhang et al. 2016 β-amyloid-induced damages Brain 50 μM Rat [197]
Zhao et al. 2017 NaF-induced injury Embryos 50–100 μM? Mouse [198]
Zhou et al. 2017 Ischemia/reperfusion injry Heart 20 mg/kg Mouse [199]
Zhu et al. 2018 Oxidative stress Heart endothelium 10 μM Rat [200]
Plants
Kobylinska et al. 2017 Lead-induced cell death Tobacco cells 200 nM Plant [201]
Wang et al. 2017 Drought stress Arabidopsis ??? Plant [202]
Xu et al. 2016 Thermotolerance Tomato plants 10 μM Plant [203]
Zheng et al. 2017 Salt-stress Plant cells — Plant [204]
Cells
Baburina et al. 2017 Aging Mitochondria 7 mg/kg/day Rat [205]
Bardak et al. 2017 2-ethylpyridine-induced stress ARPE-19 cells 200 μM Human [206]
Charao et al. 2015 Paraquat-induced toxicity A549 cells 10 μg/mL Human [207]
Chen et al. 2015 Bile acid-induced oxidative stress L02 cells 1 μM Human [208]
Fu et al. 2017 Chloranil-induced toxicity PC12 cells 25–200 μM Mouse [209]
Gurer-Orhan et al. 2016 b-amyloid-induced damage Cells 10–100 μM Hamster [210]
Han et al. 2017 Obesity-associated stress Oocytes 30 mg/kg/day Mouse [211]
Janjetovic et al. 2017 UVB-induced damage Melanocytes 50 μM Human [212]
Ji et al. 2016 Angiotensin-II-indued injury Podocytes 0.1–1 mM Mouse [83]
Jumnongprakhon et al. 2015 Methamphetamine-toxicity C6 cells 1–100 nM Rat [213]
Liu et al. 2015 Hypoxia-induced N2a cells 5 μg/mL Mouse [214]
Lu et al. 2015 LPS-induced hypertrophy Myocardial cells 1.5–6 mg/mL Rat [215]
Maarman et al. 2017 Uric acid-induced toxicity C2C12 myotubes 10 nM Mouse [216]
Miao et al. 2018 benzo(a)pyrene meiotic failure Oocytes 1 nM–1 mM Pig [84]
Mehrzadi et al. 2017 H2O2-induced toxicity MSC 10 nM–1 mM Human [85]
Ozerkan et al. 2015 CCl4-induced cytotoxicity HepG2 & Hep3B 10 nM Human [217]
Pang et al. 2017 Early apoptosis Oocytes 1 nM Bovine [218]
Sagrillo-Fagundes et al. 2016 Hypoxia-reoxygenation toxicity Trophoblasts 1 mM Human [86]
Sanchez-Bretano et al. 2017 H2O2-induced cell death 661 W cells 0.1–1 μM [219]
Song et al. 2015 LPS-induced inflammation Stem cells 100 nM Mouse [220]
Tan et al. 2016 Oxidative stress-induced cell death Adipocytes 100 μM Human [221]
Waseem et al. 2017 Oxaliplatin-induced toxicity SHSY-5Y cells 10 μM Human [222]
Wongprayoon et al. 2017 Methamphetamine-induced stress SH-SY5Y cells 0.01–1 μM Human [223]
Xie et al. 2015 Hypoxia-induced hypertrophy Cardiomycyte cell line 1 mM Rat [87]
Xue et al. 2017 Kainic-induced cell death N2a cells 50–100 μM Mouse [184]
Yang et al. 2017 Iron overload senescence MSCstem cells 10 nM–100 μM Mouse [224]
Yang et al. 2017 Glucocorticoid-induced impairment Isolated knee joints 1 μM Mouse [225]
Yu et al. 2017 Ischemia–reperfusion injury H9c2 10 μM Rat [226]
Zhao et al. 2018 Ab-induced neurotoxicity Primary neurons 0.1–100 μM Mouse [227]
Zhou et al. 2018 rotenone-induced cell death SH-SY5Y cells 50–500 μM Human [228]
Zhu et al. 2015 Myocardial infarction Adipose stem cells 5 μM Rat [229]

Table 1.

Some of the actions of melatonin observed in various pathophysiological situations.

Figure 1.

A simplistic summary of melatonin-related proteins. Melatonin is synthesized from tryptophan by a series of enzyme the the limiting step of which is catalyzed by Arylalkylamine N-acetyl transferase (green box); melatonin is excreted mainly unchanged from mammalian bodies or conjugated either by UDP-glucuronosyltranserases or by sulfotranferases, but it is also catabolized by indoleamine-2,3-dioxygenase, myeloperoxidase or cytochrome c (yellow box). At the molecular level, the targets of melatonin are mainly: Its two melatonin receptors, MT1 and MT2, QR2 (formerly known as MT3). Furthermore, putative targets might exist such as nuclear receptors and particularly Nrf2 that might explain some of the anti-oxidant capacities of melatonin (red box).

Beyond these biochemical features, melatonin has two unique features: it is very soluble but seems to travel freely through biological membranes, and its possible toxicity is extremely low (although some human cases of undesirable effects were reported), permitting scientists to give on many models very large amounts of the compound in cellulo and in vivo without apparent associated major toxicity. It was thus obvious that in many cases, the activity at those “pharmacological” dosages led to surprisingly numerous therapeutic properties of this molecule. Furthermore, the discovery that melatonin had, in cellulo and in vivo, antioxidant properties added to the multiple possibilities of use of melatonin, leading to this apparent paramount of therapeutic properties.

Advertisement

2. Melatonin synthesis

Melatonin is mostly synthesized starting from tryptophan in the pineal gland by a series of enzymes, the limiting one being arylalkylamine N-acetyltransferase (AANAT) also known as the timezyme [6]. Many studies have been performed on this enzyme and its requirements in terms of substrate specificity and inhibitor research, in particular in human [7, 8]. Over the years, several groups hypothesized and reported the possibility that melatonin was also synthesized in mitochondria (see also below, Section 6.4), suggesting that the antioxidant properties of the molecule would confer a strong resistance of mitochondria to the generation of ROS, a common feature of those subcellular organelles. Indeed, if the dogma was, in the 1950s and later on, that melatonin was mainly synthesized in the pineal gland, a fact that was clearly confirmed by surgical removing of the gland would lead to a major reduction of circulating melatonin and to the loss of some of the circadian and circannual rhythms; several papers co-indicated that such local synthesis that does exist should be taken into consideration (see, for instance, Stehle et al. [9]). What is more troubling is the recent precise description of melatonin synthesis in mitochondria, at least in brain-derived organelles [10] as well as the presence of a functional GPCR (MT1). Intuitively, many previous strong knowledge would go against the finding that melatonin is synthesized in mitochondria, even if that was recently restricted to brain-derived mitochondria [11]. But melatonin is also known to “travel” freely inside membranes. Thus in order to stay inside mitochondria, it should be sequestered inside them in order to prevent the damages of ROS production—a common and key feature of the respiratory chain—thanks to the antioxidant properties of melatonin (see below, Section 6.1.2, for further discussion).

No revolution, nevertheless, occurred in the way melatonin is synthesized. It comes from several steps. All those enzymes have been cloned and studied, including from human origin. The particular case of AANAT catalyzing the limiting step of the synthesis has been at the source of the seminal work of David Klein’s laboratory (see, for instance [6, 7]). This enzyme is destroyed during the day and active only at night. The way it is regulated is different according to species, but it seems a formidable waste of energy to handle it that way (synthesis and immediate destruction for “nothing”) [12, 13], strongly suggesting by the way this pathway is regulated that it is of major importance for physiology. The enzyme was cloned in our laboratory, and a thorough study of its substrate and co-substrate specificities was reported [8]. It was attempting, at one stage, to try to find specific inhibitors of the enzyme, in order to better understand in in situ situations the roles of melatonin at various locations. Several publications including ours reported those efforts [14, 15, 16, 17, 18]. If one particular point should be stressed, it is the elegant ways analogues of an intermediary state of the substrate/co-substrate complex permitted to turn molecules into powerful inhibitors, although overall fragile ones [19], as well as the way that the incorporation of an exotic amino acid in place of a serine permitted to stabilize the enzyme, rendered insensitive to proteolysis [20, 21, 22].

Advertisement

3. Melatonin receptor molecular pharmacology

3.1. Melatonin receptors

To somewhat summarize the situation, there were two GPCRs (MT1 and MT2) found throughout the animal kingdom, an elusive binding site (MT3) that turned out to be an enzyme—quinone reductase 2 (QR2) [23] (see below, Section 6.3), another receptor (Mel1c) that was present in fishes, birds, and reptilians and that evolved to a GPR50 in mammals [24], with the curious property to have lost the recognition of melatonin, with a single exception (in platypus [25]), and finally the elusive nuclear receptovr, first described by Becker-André et al. [26] and then retracted [27]. Several other research papers [28] pointed at nuclear receptor(s) to explain the circadian rhythm of some key metabolism enzymes that could logically be dependent on the circadian rhythm of melatonin (see discussion in Jan et al. [29]).

What are the most characterized in the melatonin field, besides the multiple functions of the molecule itself (see below), are the binding characteristics at its receptors. The receptors were first discovered and cloned/characterized by Reppert’s group [30] from both hamster and human. This première was followed by a series of cloning, including the discovery that hamster had only one functional melatonin receptor [31], to the contrary of most of the mammals that possess two (MT1 and MT2): human, rat, mice, sheep (although it was long believed to possess also a single receptor form [32]), etc. Cloning was also reported for other species, including birds and fishes [33, 34] and probably insects [35]. This led to the possibility to establish the binding pharmacology of those receptors in several laboratory species—mouse [36], rat [37], and sheep [32]—as well as in human [38]. For years, then, our goal has been to synthesize analogues of melatonin and use them to better understand the MT1 and MT2 roles, as well as to be able to somehow modulate them. It is not the place, here, to review the chemistry that has been explored around melatonin, but recent reviews could be looked at: Mor et al. [39], Garrat and Tsotinis [40], Rivara et al. [41], and Zlotos et al. [42]. The field would have benefit from a quest of specific and stable in vivo binders, particularly antagonists, permitting to explore and understand the limit of the melatonin actions, at least through these particular targets.

Incidentally, one must point out that there are still no antibodies against the receptors. We and many others tried over the last decades to produce such tools with a general negative endpoint. This, of course, has been an obstacle to a better understanding of those receptors. Nevertheless, the repartition of the receptors in various organs, and particularly throughout the brain, has been nicely reviewed by Ng et al. [43] with some precisions of their respective functions: these seem to be as follows—improvement of neurogenesis (hippocampus with a memory maintenance via the inhibition of long-term potentiation by MT2 receptor); MT1 would regulate the REM sleep; MT1 would also confer a protection against Huntington disease. In terms of melatonin receptor actions, those are the strongest information available. It seems clear, for example, that most of the protection offered by melatonin in multiple pathological situations (as summarized in Table 1) are not mediated by its receptors.

It would be very complicated to be exhaustive in terms of characterization of those binding sites, as the data is scattered throughout the literature. What is “easy” is that we and others using the binding assay developed around Vakkuri et al.’s 2-[125I] iodomelatonin [44] for establishing the basic molecular pharmacology of the MT1 and MT2 receptors from several key laboratory species and from humans, but basic data can be found in Jockers et al. [45].

In the next sections, three aspects must be covered: the binding, heterodimerization, and structure of the melatonin receptors.

3.2. Binding, functionality, and heterodimerization

Initially, several reports were done using [3H]melatonin, but the specific activity of the tracer was not sufficient to gain robust information on the receptors. It is only recently that heavily labeled [3H]melatonin became available. This radiotracer permitted to better understand the various states of the receptors and their behavior in that context [46]. Historically the binding studies were largely facilitated by the use of the super-agonist, 2-[125I]-iodomelatonin [44]. Not only this compound is easy to synthesize, but its sensitivity counteracted the very high affinity of melatonin for its receptors, as well as the paucity of the expression of these receptors in relevant tissues. Almost all the laboratories involved in melatonin research have been using this radiotracer. It must be pointed out, though, that attempts to use alternative ligands have been reported, mainly in the spirit of using specific ligands of one or the other of melatonin receptors [47]. Unfortunately, only ligands specific of MT2 have been reported, so far. MT1-specific binders have been elusive, despite the wide variety of melatonin analogues that have been synthesized. As stated elsewhere in the present essay, the main focus of chemistry research in this melatonin domain over the last decades was to find alternative ligand agonists at the receptors with strong stability in vivo.

Functionality of seven-transmembrane domain receptors is a complex science, providing daily new data. The number of coupling pathways at receptors in general is important, and more are discovered often. An excellent review has been published very recently [48], and the contribution of the same authors to the IUPHAR compendium on melatonin receptor functionality [45] should be considered as reference documents to understand the various pathways, at least as of today.

Nevertheless relatively few publications address the functionality of ligands in a global way. Indeed, if some functional data has been produced around a series of chemical analogues completing the classical binding displacement approach, rather few address the global and “standardized” characterizations of a series of ligands on MT1 and/or MT2. There are cases where given compounds were characterized as partial agonists that turned out to be inverse agonists instead [49], leading to a yet another level of complexity of melatonin receptor pharmacology. We recently embarked in such a task, by screening the agonist/antagonist behavior of a series of compounds (Legros & Boutin, in preparation) after assessing the various methods [50]. We also extended these coupling measurements to a small series of potential antagonists specific of MT2 [51], to conclude that the compounds were not antagonists but rather partial agonists. As stated and described by Kenakin [52], one should further dig the concept of biased ligands. Indeed, it seems clear, now, that some at least of the downstream pathways of melatonin receptors are elicited by some agonist ligands while not by other ones. This concept has been a bias of the approach to melatonin research. Indeed, while seeking for tools to understand these pathways and their implications in various pathological models, we never had access to real, stable, and potent antagonists, despite past claims for such compounds [53, 54]. Even when large-scale screening campaigns were attempted [55], the poor affinity (compared to the already existing compounds: low μM affinity in the best cases versus low nM already available ones) of those newly discovered compounds was not in favor of trying to develop series of chemicals around those hits. A similar situation occurred when we attempted to find peptide ligands at melatonin receptors [56].

After the first evidences that crystallogenesis of membrane proteins would be a challenge, we thought we would continue to search for ligands with a trial-and-error approach as we did for years, without the help of the visualization of the compounds in the protein as it became “mundane” these last years concerning co-crystallizations of compounds in their soluble protein targets. By multiplying the number of ligands in attempts to better describe the topography of the melatonin-binding site, even using mutagenesis [57, 58, 59, 60], we also multiplied the assays on the functionality of the receptors, because we more and more discovered the ways the receptors were transferring their message to the cell. The simplistic view that a handful of such pathways between the receptors and the inner cell existed became obsolete. The by-product of such variety was that we found biased ligands that activated one but not the other(s) signaling pathways downstream melatonin receptor, as it is briefly discussed elsewhere.

Then, another new aspect came up: receptors can dimerize, a feature that was known for quite some time (see Rodbell [61], and see seminal review by Bockaert and Pin, [62]). Even though it was often believed to be an artifact of the purification attempts, the reality of such structures in situ was evidenced when one realized and demonstrated heterodimerisation between various types of such receptors: heterodimers between isoforms of a receptor, GABA [63], heterodimers between two unrelated GPCRs or even between GPCR, and another type of protein [64]. A paramount of examples were published, and their studies were made possible using the BRET technology [65]. In brief, engineering two receptors to make each of them fused with a carefully chosen fluorescent protein leads to a system in which the excitation of one of them results in the emission of fluorescent in the region exciting the other one. This cannot occur if the proteins are not physically in a very close vicinity of one another. Melatonin receptors have been also shown to be able to dimerize with serotonin 5HT2c receptor [66], as well as between MT1 and MT2 [67] or between MT1 and GPR50 [68], the melatonin-related receptor (evolved from Mel1c [24] and that has lost its property to bind melatonin [69]). More recently, the heterodimerisation of GPR50 and the transforming growth factor-β receptor [70] potentially open interesting routes toward the role of this orphan receptor as well as its implication in cancer development. Obviously many control experiments should be run in these explorations, as it would be attempting to conclude that any receptor can dimerize—and thus regulate the signaling pathway of—any other receptor (see Damian et al. [71] for a counter example, among some others).

3.3. Purification/structure

Attempts to crystallize GPCRs have been done for years with various successes. Beside several reports of models of the receptors [72, 73, 74], that turned to be more or less disappointing because they poorly brought new information—somewhat as expected. Thus, several lines of strategies were further explored. One of them led to a pure, functional MT1 receptor, after several years of technical challenges: expression, stabilization, purification, and functionality measurement [75, 76]. We embarked several years ago in an approach that attempted to be original: as a first step in this purification/crystallization of melatonin receptor(s) project, we cloned melatonin receptors from as many and as various species as possible. Many such melatonin receptors have been reported in the literature, such as various sheep strains, buffalo, fishes, and even coral, many of which has been deposited in GenBank but not described in a publication. The rationale behind this Noah-ark type of research was to systematically use melatonin receptors from those variously evolved species (birds, reptilians, mammals from various environments, some harsh insects, etc.) that have in common their capacity to recognize melatonin—by definition. We aimed at comparing their thermal stability once they were stably expressed in CHO cells. We would choose the most resistant one and use that as a model in the process of purification/reconstitution established previously by Logez et al. in our laboratory [75, 76]. Despite a few success [25], we terminated the program for resource limitation reasons.

Advertisement

4. Melatonin catabolism

Melatonin catabolism has been described and discussed in-depth by Hardeland throughout the living kingdom [77]. In short, the main route of melatonin elimination (from the body) is not catabolism but rather conjugation and excretion via the urine. Thus there are three ways to consider: (i) the unchanged melatonin that one can find in urine; (ii) the conjugates, mostly glucuronides and sulfates; and (iii) the catabolism itself. Catabolism means that the molecule is transformed into something quite different from the original molecule. For example, in melatonin case, several reports demonstrated the opening of the indol ring. This opening possibly occurred through cytochrome c [78] or through 1,2-dioxygenase [79]. This was of importance because not too many compounds bear a formyl moiety such as the one produced during the cleavage of the indol cycle by either of these enzymes. This catabolism process would generate several products including N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and N1-acetyl-5-methoxykynuramine (AMK) [80]. The same paper, though, pointed out the absence of such metabolite(s) in human urine, strongly suggesting that the main catabolic route of melatonin would rather be through conjugation, even after oxidative stress.

Advertisement

5. The melatonin paradox

The field suffered from two paradoxes: safety and high affinity to natively poorly expressed receptors. First, melatonin is a very safe molecule, as far as we know; there is no report of human toxicity for overdose, and in mice the lethal dose is superior to 800 mg/kg [81]. Nevertheless, the French Agency for Food, Environmental and Occupational Health & Safety (www.anses.fr) emitted a report—in French—pointing at several cases of toxicity linked to melatonin consumption. Although they were ~100 cases in France reported during a 30-year period survey (i.e., a relatively modest number of cases, some of which have not been univocally linked to melatonin intake), the literature on clinical trials of melatonin is large enough to consider melatonin as reasonably safe [82], with the usual cases of deliberate overdose. In any case, it is not unusual to find reports in the literature where the dosage of melatonin in vivo or in cellulo is important. It was reported at several occasions—even if it probably depends on the cell type—cells treated with 1 mM of melatonin without apparent cell toxicity and even, in some cases, with beneficial effects [83, 84, 85, 86, 87]. Why is it a flaw? Because one can treat almost anything with this compound, at almost whatever dosage, and observe something, including relevant benefits for the situation (see Table 1 and further examples in Boutin [88]). Furthermore, melatonin has a friendly behavior in terms of pharmacokinetics. When compared to another multi-card compound, resveratrol, it seems that unlike it, melatonin circulates in the blood after oral consumption at a fairly high concentration, while only 1 to 2% of resveratrol was found at the peak after ingestion of 25 mg/kg of resveratrol [89].

Finally, as stated elsewhere in the present essay, the affinity of melatonin for its receptors is in the low nanomolar range [45]. Many strict analogues have been synthesized with similar high affinities for the receptors. Thus, it has been complicated and sometimes impossible to start new chemical programs ad initio, or at least starting from molecules issued from high-throughput screening campaigns, for example, from which hits are rather in the high micromolar range. Therefore, new compounds with unexpected structures have been slowly emerged in the field. As a representative example, D600 (hydroxyl-verapamil) is one of the few compounds showing strong specificity for MT1 [90]. No chemical program to date has been published to explore this observation and to deliver a specific ligand at MT1 receptor with some pharmacological properties (and specificity) rendering it amenable to in cellulo or in vivo experiments.

Advertisement

6. Melatonin actions

6.1. Overall

Melatonin is the core master of rhythms. This part of the story is beyond any doubt. It translates the succession of days (light) and night (darkness) to the body. In the absence of light, the pineal gland (and more particularly the AANAT, the limiting step of melatonin biosynthesis) synthesizes melatonin. Nevertheless, a report [91] shows that, at least in the European hamster, the circannual rhythm could be maintained even after pinealectomy, thanks to light action in an accelerated photoperiodic regime, demonstrating the hypothalamic integration of the photoperiodic signal even in pinealectomized animals and, thus, in the absence of pineal gland synthesis of melatonin.

Melatonin circadian rhythm can be measured in the blood from healthy volunteers and is clearly linked to the successions of days and nights. The timezyme (AANAT) is the master key of this process: active during dark periods and inactive during day (as the enzyme is destroyed by the light-induced proteasome).

6.1.1. Foreword

Melatonin exerts protective actions far beyond mammals, as several reports showed the role of melatonin in protecting yeast [92], bacteria [93], zebrafish [94], and plants [95] from various types of insult. For a discussion of melatonin throughout evolution, see also Tan et al. [96]. For decades, melatonin has been described as a compound able to fight almost any pathological situations. Tekbas et al. [97] even seriously considered melatonin as an antibiotic and Anderson et al. as an anti-Ebola virus agent [98]. A sample of those numerous actions can be found in Boutin [88], up to 2015. Table 1 of the present essay is the follow-up of that particular list of beneficial properties. Many of those properties of melatonin seem to be linked to the capacity of the compound to limit reactive oxygen species (ROS) actions. ROS have been first documented as an “infamous” group of highly reactive molecules responsible for oxidative stress. In an enlightening review, Roy and coworkers [99] defined the field of reactive oxygen species, by starting to recall that ROS are also regulating signaling pathways in physiological situations. They also emphasized the fact that treatments with so-called antioxidants failed to show efficacy or/and positive effects in the prevention of diseases or health complications coming from oxidative stress. Nevertheless, it seems that according to a common belief, melatonin falls outside that particular category and is the ultimate scavenger/antioxidant molecule that has multiple capacities to prevent almost any diseases.

It is sometimes complicated to find common sense in such a plethora of actions. Table 1 lists some of these many actions, as published between 2015 and today. There is no way to be able to understand why melatonin has been reported for so many years in so many pathological situations. And the purpose of the present essay is not to do so. It is rather to make a compendium of those actions and to let the community know that such papers exist and that the reason why melatonin is so ubiquitously active remains a mystery.

It is attempting, though, to make a rapid survey of those publications and to conclude that the common factor is the production of ROS. Then, we can hypothesize that most of these beneficial actions were due to a capacity of melatonin to induce antioxidant enzymatic defenses. To conclude on this working hypothesis, one will have to identify the nuclear receptor mediating this property. Nuclear factor erythroid 2-related factor 2 (Nrf2) might be a good candidate, but a wishful thinking is certainly not a proof of fact.

6.1.2. Melatonin as an antioxidant molecule

Forman et al. in two seminal papers explained that the notion of hydroxyl radical scavengers is an extreme case of wishful thinking [230, 231]. Later on, he and his coworkers clearly showed that a unique molecule could not be a scavenger of superoxides, hydrogen peroxides, or other hydroperoxides or hydroxyl radicals. Indeed, all chemicals inside a cell react chemically with radical species, that is, proteins, lipids, nucleic acids, etc. Thus, because all organic compounds react with radicals with rate constants approaching the diffusion limitation, no compound can be better than the sum of the others to scavenge those ROS [231]. This can apply to melatonin. Like many other chemicals, whether indol-based or not, this compound, even at large concentrations, cannot be, per se, a scavenger. Therefore claims that melatonin is a super scavenger, with many advantages over other similar naturally occurring compounds, must be taken with extreme caution, despite several in-depth reviews, such as the one by Galano et al. [232]. Even the use of “direct” detection methods of radicals (to prove this hypothesis) should be handled with much caution [233]. Nevertheless, melatonin sustains antioxidant properties (see Rodriguez et al. [234] for review). Indeed, it can increase the expression of antioxidant enzymes (see, e.g., Mahrzadi et al. [149] and references therein). Melatonin can also act as a potent antiapoptotic agent in many cells [235], maybe through an antioxidant type of activity, as a relationship between ROS and apoptosis and autophagy has been well documented. How can melatonin induce those antioxidant defenses?

6.1.3. Melatonin as a ligand of Nrf2?

At the time (2003) Rodriguez et al. wrote their review [234] on antioxidant capacities of melatonin, Nrf2 was not really an identified and recognized partner in this process. The relationship between melatonin actions and the role of nuclear factor erythroid 2-related factor 2 (Nrf2) has been reported more than 50 times in the literature these last years, starting around 2009 [236]. Nrf2 is a key factor in the induction of antioxidant protein defenses of the cell. It binds to a region called EpRE—also known as ARE [230]. This transcription factor (belonging to the huge family of Cap’n’collar transcription factors) is neutralized in cellulo by another factor, Kelch-like ECH-associated protein 1 (Keap1). The heterodimer is directed to the proteasome where the proteins are destroyed. Upon some conditions, including pharmacological ones (for instance, sprout-derived chemicals [237]), the dimer is open, and the free Nrf2 migrates to the nucleus of the cell where it associates with the EpRE region. This translates by the induction of several key proteins of the antioxidant cellular armada, such as heme oxygenase 1, quinone reductase 1, glutathione S-transferase π1, etc., but also enzymes from the phase 2 drug metabolism, such as UDP glucuronosyltransferases. There is a large literature indicating that melatonin induces Nrf2 expression and/or its separation with its corepressor, Keap1 (about 50 publications reported at least the induction of Nrf2 by melatonin). Furthermore, it has been shown several times that upon melatonin treatment, the cytosolic Nrf2 migrates to the nucleus where it can exert its inductive function. One question remains unanswered, though; it is the possibility that Nrf2 was the elusive nuclear factor described at several occasions [26]? Unfortunately, the tridimensional structure of Nrf2 and/or of its complex with Keap1 has not been reported. It seems that Nrf2 has no a priori structure and is only adopting define 3D shape either once linked to Keap1 (a complex that is then directed to the proteasome) or when in complex with a ligand. Much more need to be done to understand this relationship that might enlighten part of the observation of Table 1.

6.2. Through MT1/MT2

The specificity of actions linked to the binding of melatonin to one of its receptors, MT1 and MT2, is still a matter of debate. Indeed, a thorough survey of its action is not possible in vivo in wildtype animals, because we are still lacking reliable and isoform-specific antagonists (see discussion in Jockers et al. [45]). It is possible, though, to study the role of one or the other of the receptors using either natural KO animals [such as the Siberian hamster, but not the European hamster (Gautier & Boutin [281])] or, alternatively, MT1 or MT2 (or both) KO animals, which have been engineered [238, 239, 240], but results are slow to be issued [241, 242, 243] (see also discussion in Jockers et al. [45]). Nevertheless, general conclusions can be drawn from accumulated data, as reviewed by the same authors [45]. It is difficult, as of today, without drowning in the 3970 available reviews on melatonin, to clearly segregate between the subtype roles. Among the clearest facts, mice lacking MT1 receptors exhibit higher mean blood glucose levels than wildtype mice [244]. Those KO animals tend to be more glucose intolerant and insulin resistant than their wildtype counterparts. Through many different parameters, both MT1 and MT2 receptors seem to have a role in the phase shift of circadian rhythms, as demonstrated by several lines of indications, including knockout animals, the use of specific MT2 antagonists (luzindole, 4P-PDOT), as well as ex vivo experiments. Melatonin can activate an immune response. Remarkably, that was proposed as early as 1926 by Berman. This activity seems to depend on the MT1 receptor [245], but opposite claims have also been published [246]. Liu et al. showed that it was MT2 that was the receptor implicated in axogenesis and the formation of functional synapses [247].

Nevertheless, it seems to me improbable that even only some of the actions in Table 1 were through the binding of melatonin onto its receptors.

6.3. Through QR2

As stated previously, it was rapidly discovered that two melatonin-binding sites were GPCR in mammals and an extra one, Mel1c, in reptilians and birds. The group of Dubocovich also pointed at a binding site, ML2 [248, 249], with rather unconventional properties (particularly with very fast exchange) baptized MT3. In 1999 we embarked in an attempt to clone this particular receptor, after having obtained similar results for the pharmacological description of this particular “receptor” [250]. We had the chance to identify it by using a series of inverse pharmacology techniques, comprising an analogue of a specific MT3 ligand, MCA-NAT, on which affinity chromatography succeeded. The binding site was an enzyme with a peculiar story, quinone reductase 2 (QR2 a.k.a. NQO2) [23]. The activity of this enzyme was first described in the early 1960s as a reductase using unconventional donors as co-substrates, such as N-benzyl, N-methyl, or N-ribosyl dihydronicotinamides, and Talalay’s group established that the enzyme was the enzyme once described by Liao et al. [251]. Interestingly, they clearly established the nature of the enzyme and particularly its incapacity to recognize NADH or NAD(P)H as co-substrates, as well as its sensitivity to some chemical, in an orthogonal way to QR1. For instance, QR2 is insensitive to the reference QR1 inhibitor, dicoumarol. When we discovered that QR2 was indeed MT3, we had to reinforce this observation by generating KO cell lines [252], KO mouse strain [253] and various tools that would help to understand the potential role of this enzyme (see Vella et al. [254] and references there in). Although the enzyme was identified during a pure melatonin-related program, it turned out to have nothing in common, a priori, with the melatoninergic systems. Indeed, while able to bind melatonin with a rather strong affinity—in the nM range—QR2 is only poorly inhibited by melatonin, in the 50 μM range, suggesting that melatonin regulation was not a player in the QR2 game. Indeed, as often in the drug metabolism area, enzymes from both phases I and II, such as cytochrome P450, UGTs, or glutathione S-transferases, are often enzymes with enough plasticity in their catalytic sites in order to accommodate xenobiotics that are, by definition, molecules of various chemical structures issued from the environment at large.

Nevertheless, I suggested that QR2 inhibition at high dose of melatonin could be an explanation for melatonin exerting its antioxidant capacities [88].

6.4. Through mitochondria

Incidentally, a couple of papers reported not only the synthesis of melatonin in mitochondria but also the presence in these organelles—at least those isolated from the brain—of a measurable binding, signing the presence of MT1 receptors. Again, as long as the mitochondrial DNA is not reported for genes encoding for these GPCRs, it seems possible to hypothesize that those binding sites were a leftover from the brain preparation of mitochondria, a possibility reinforced by the difficulty of preparing “pure” mitochondria from these lipid- and membrane-rich organs. Beyond these hypothetical technical considerations lays also the fact that our laboratory had experienced “very” often cells with no binding activity, suggesting that mitochondria would express melatonin receptors only in melatonin receptor-rich organs—such as the brain—an indirect suggestion that the presence of those receptors in these organelles might be a “simple” signature of a difficult separation between all the kinds of membranes present in a neuronal cell. There were several reports over the last decade showing a protective effect of melatonin onto mitochondria functions (see Table 2). Then several reviews suggested that melatonin was synthesized by mitochondria (see, for instance, Manchester et al., 2015 [255], Reiter et al., 2017 [256] and 2018 [257]). Particularly interesting is the fact that Cellular and Molecular Life Science published a special issue in 2017 (volume 74, issue 21) dealing with melatonin and mitochondria, emphasizing the interest of the community for these observations and their consequences. A reason for this hypothesis was given: mitochondria, like chloroplasts in plants, evolved from bacteria. Because originally cyanobacteria were subjected to heavy exposition to toxic free radicals, they evolved in keeping melatonin as an antioxidant, scavenging these radicals and thus preserving their integrity. Because this happened about 3 billion years ago, melatonin has been selected to protect and defend those microorganisms.

Protection against Authors Year Reference
Doxorubicin Xu and Ashraf 2002 [258]
Oxidative stress Jou et al. 2004 [259]
NO synthase induced dysfunction Escames et al. 2006 [260]
Apoptosis Han et al. 2006 [261]
Ischemia-Reperfusion Petrosillo et al. 2006 [262]
Apoptosis Luchetti et al. 2007 [263]
Oxidative stress Jou et al. 2007 [264]
UV exposition Fischer et al. 2008 [265]
Aging Petrosillo et al. 2008 [266]
Oxidative stress Hibaoui et al. 2009 [267]
Permeability transition Jou et al. 2010 [268]
Permeability transition Jou et al. 2011 [269]
Bisphenol A Anjum et al. 2011 [270]
CCl4 Chechshevik et al. 2012 [271]
Isoproterenol Mukherjee et al. 2012 [272]
Ischemia-Reperfusion Yang et al. 2013 [273]
UV exposition Canonico et al. 2013 [274]
Demyelination induced stress Kashani et al. 2014 [275]
Cd Guo et al. 2014 [276]
Isoproterenol Mukherjee et al. 2015 [272]
Ischemic-Stroke Yang et al. 2015 [277]
Lipid toxicity Ozsoy et al. 2016 [159]
Aging Baburina et al. 2017 [205]
Lipid toxicity Das et al. 2017 [116]
Paclitaxel Galley et al. 2017 [124]
Copper Ghosh et al. 2017 [126]

Table 2.

Melatonin protects mitochondria against various stresses.

Of course, when bacteria colonized eukaryotic cells, the trait was maintained throughout evolution, including in mammals. Thus, no matter how high or low the blood melatonin concentration is, this particular intra-mitochondria concentration remains constant (not depending on the circadian rhythm), protecting mitochondria from the never ending production of free radicals that is the signature of sane mitochondria. An impressive series of publications were issued in these last few years (see Table 2) dealing with situations where toxicity was prevented by melatonin. This can be further extended to the protection afforded by mitochondria-synthesized melatonin to oocytes [278]. Finally, one can also add the observation that mitochondria melatonin protects plants from drought episodes [202]. Particularly interesting was the last one in which Suofu et al. [10] demonstrated the presence of the main melatonin synthesis enzymes, arylalkylamine N-acetyltransferase (AANAT) and acetylserotonin O-methyltransferase (HIOMT), in mitochondria matrix, as well as the high concentration of melatonin inside those mitochondria matrix. Furthermore, they showed the presence of MT1 receptor and the actual coupling of this receptor, turning this observation into a major progress in the domain, as rare are the receptors signaling in the mitochondria. This observation was challenged by Ahluwalia et al. [279] (replied by Suofu et al. [11]) that was able to show the presence of the melatonin receptors in muscle fibers, but not in mitochondria thereof. It is clear that this breakthrough information will be better understood after the observation will be confirmed independently. Of course, questions remain in the skeptical reader mind: if the melatonin system evolved from bacteria over several billion years, then the genetic material should have evolved together with it, meaning that the mitochondrial DNA should encode for MT1, AANAT, and ASMT, which does not seem to be the case. This observation would also lead to an extra complexity involving the protein importation system (TOM, Tim, etc.) and the ad hoc addressing sequence(s) onto those proteins, all of which have not been seen so far. Furthermore, the discovery and description of an inward transport of melatonin in mitochondria [280] are not fitting an in situ synthesis. For those of us who have been working with subcellular organelles, it is very hard to assess the purity of those organelles because of the continuum that exists between all the membranes from cells. One should also add to this the particular complexity of the brain tissue that is by essence very lipid-rich, leading to an extra difficulty in preparing pure membranes or pure subcellular organelles. Nevertheless, the several evidences on the melatonin actions at the level of mitochondria cannot be doubted and change our view of its role and of the role of MT1, as MT2 seems to be absent from the organelle.

Advertisement

7. Future paths?

Trying to summarize the literature on subjects like melatonin is obviously impossible. One will give his/her view on some of the points that are the most attractive to him/her. It was thus vain to attempt to solve issues with such an essay on this neurohormone. The future will tell if melatonin is an exceptional molecule with many capacities. What is clear, as of today, is that melatonin has been described on a plethora of situations with beneficial endpoints. If melatonin is an antioxidant—but the concept behind this word is different from one author to another—it is not as a scavenger of radical oxygen species, but most probably through its capacity to induce cellular defenses against oxidative stress. Melatonin has different known targets; two, MT1 and MT2, are well described, but these receptors bring more unexpected novelties over the years, an enzyme—QR2—the study of which could be part of an explanation for the antioxidant properties of melatonin, and, finally, a pathway, linked to Nrf2 that seems to be another part of the explanation for these properties. There are many routes still to explore to understand what is behind this molecule, and the spectacular associated with it should be concealed and mastered until beyond (and despite) our hopes; facts will be revealed.

References

  1. 1. Majidinia M, Reiter RJ, Shakouri S-K, Mohebbi I, Rasteghar M, Kaviani M, Darband SG, Jahanban-Esfahlan R, Nabavi SM, Yousefik B. The multiple functions of melatonin in regenerative medicine. Ageing Research Reviews. 2018;45:33-52. DOI: 10.1016/j.arr.2018.04.003
  2. 2. Zisapel N. New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation. British Journal of Pharmacology. 2018; in press. DOI: 10.1111/bph.14116
  3. 3. Pevet P, Klosen P, Felder-Schmittbuhl MP. The hormone melatonin: Animal studies. Best practice & research. Clinical Endocrinology & Metabolism. 2017;31:547-559. DOI: 10.1016/j.beem.2017.10.010
  4. 4. Tordjman S, Chokron S, Delorme R, Charrier A, Bellissant E, Jaafari N, Fougerou C. Melatonin: Pharmacology, functions and therapeutic benefits. Current Neuropharmacology. 2017;15:434-443. DOI: 10.2174/1570159X14666161228122115
  5. 5. Liu J, Clough SJ, Hutchinson AJ, Adamah-Biassi EB, Popovska-Gorevski M, Dubocovich ML. MT 1 and MT 2 melatonin receptors: A therapeutic perspective. Annual Review of Pharmacology and Toxicology. 2016;56:361-383. DOI: 10.1146/annurev-pharmtox-010814-124742
  6. 6. Klein DC. Arylalkylamine N-acetyltransferase: “the Timezyme”. The Journal of Biological Chemistry. 2007;282:4233-4237. DOI: 10.1074/jbc.R600036200
  7. 7. Ganguly S, Gastel JA, Weller JL, Schwartz C, Jaffe H, Namboodiri MA, Coon SL, Hickman AB, Rollag M, Obsil T, Beauverger P, Ferry G, Boutin JA, Klein DC. Role of a pineal cAMP-operated arylalkylamine N-acetyltransferase/14-3-3-binding switch in melatonin synthesis. Proceedings of the National Academy of Sciences. 2001;98:8083-8088. DOI: 10.1073/pnas.141118798
  8. 8. Ferry G, Loynel A, Kucharczyk N, Bertin S, Rodriguez M, Delagrange P, Galizzi JP, Jacoby E, Volland JP, Lesieur D, Renard P, Canet E, Fauchère JL, Boutin JA. Substrate specificity and inhibition studies of human serotonin N-acetyltransferase. The Journal of Biological Chemistry. 2000;275:8794-8805
  9. 9. Stehle JH, Saade A, Rawashdeh O, Ackermann K, Jilg A, Sebestény T, Maronde E. A survey of molecular details in the human pineal gland in the light of phylogeny, structure, function and chronobiological diseases. Journal of Pineal Research. 2011;51:17-43. DOI: 10.1111/j.1600-079X.2011.00856.x
  10. 10. Suofu Y, Li W, Jean-Alphonse FG, Jia J, Khattar NK, Li J, Baranov SV, Leronni D, Mihalik AC, He Y, Cecon E, Wehbi VL, Kim J, Heath BE, Baranova OV, Wang X, Gable MJ, Kretz ES, Di Benedetto G, Lezon TR, Ferrando LM, Larkin TM, Sullivan M, Yablonska S, Wang J, Minnigh MB, Guillaumet G, Suzenet F, Richardson RM, Poloyac SM, Stolz DB, Jockers R, Witt-Enderby PA, Carlisle DL, Vilardaga J-P, Friedlander RM. Dual role of mitochondria in producing melatonin and driving GPCR signaling to block cytochrome c release. Proceedings of the National Academy of Sciences. 2017;114:E7997-E8006. DOI: 10.1073/pnas.1705768114
  11. 11. Suofu Y, Carlisle DL, Vilardaga J-P, Friedlander RM. Reply to Ahluwalia et al.: Contributions of melatonin receptors are tissue-dependent. Proceedings of the National Academy of Sciences of the United States of America. 2018;115:E1944. DOI: 10.1073/pnas.1800449115
  12. 12. Foulkes NS, Whitmore D, Sassone-Corsi P. Rhythmic transcription: The molecular basis of circadian melatonin synthesis. Biology of the Cell. 1997;89:487-494
  13. 13. Schomerus C, Korf HW, Laedtke E, Weller JL, Klein DC. Selective adrenergic/cyclic AMP-dependent switch-off of proteasomal proteolysis alone switches on neural signal transduction: An example from the pineal gland. Journal of Neurochemistry. 2000;75:2123-2132
  14. 14. Ferry G, Boutin JA. High-capacity screening of arylalkylamine n-acetyltransferase inhibitors using a high-performance liquid chromatography system. Journal of Biomolecular Screening. 2000;5:361-368. DOI: 10.1177/108705710000500508
  15. 15. Beaurain N, Mésangeau C, Chavatte P, Ferry G, Audinot V, Boutin JA, Delagrange P, Bennejean C, Yous S. Design, synthesis and in vitro evaluation of novel derivatives as serotonin N-acetyltransferase inhibitors. Journal of Enzyme Inhibition and Medicinal Chemistry. 2002;17:409-414. DOI: 10.1080/1475636021000005721
  16. 16. Mesangeau C, Yous S, Chavatte P, Ferry G, Audinot V, Boutin JA, Delagrange P, Bennejean C, Renard P, Lesieur D. Design, synthesis and in vitro evaluation of novel benzothiophene derivatives as serotonin N-acetyltransferase (AANAT) inhibitors. Journal of Enzyme Inhibition and Medicinal Chemistry. 2003;18:119-125. DOI: 10.1080/1475636031000093552
  17. 17. Lepailleur A, Lemaître S, Feng X, Sopkova-de Oliveira Santos J, Delagrange P, Boutin J, Renard P, Bureau R, Rault S. Receptor- and ligand-based study on novel 2,2′-Bithienyl derivatives as non-Peptidic AANAT inhibitors. Journal of Chemical Information and Modeling. 2010;50:446-460. DOI: 10.1021/ci9004805
  18. 18. Zheng W, Cole PA. Novel bisubstrate analog inhibitors of serotonin N-acetyltransferase: The importance of being neutral. Bioorganic Chemistry. 2003;31:398-411
  19. 19. Szewczuk LM, Saldanha SA, Ganguly S, Bowers EM, Javoroncov M, Karanam B, Culhane JC, Holbert MA, Klein DC, Abagyan R, Cole PA. De novo discovery of serotonin N-acetyltransferase inhibitors. Journal of Medicinal Chemistry. 2007;50:5330-5338. DOI: 10.1021/jm0706463
  20. 20. Zheng W, Zhang Z, Ganguly S, Weller JL, Klein DC, Cole PA. Cellular stabilization of the melatonin rhythm enzyme induced by nonhydrolyzable phosphonate incorporation. Nature Structural Biology. 2003;10:1054-1057. DOI: 10.1038/nsb1005
  21. 21. Zheng W, Schwarzer D, Lebeau A, Weller JL, Klein DC, Cole PA. Cellular stability of serotonin N-acetyltransferase conferred by phosphonodifluoromethylene alanine (Pfa) substitution for Ser-205. The Journal of Biological Chemistry. 2005;280:10462-10467. DOI: 10.1074/jbc.M412283200
  22. 22. Scheibner KA, de Angelis J, Burley SK, Cole PA. Investigation of the roles of catalytic residues in serotonin N-acetyltransferase. The Journal of Biological Chemistry. 2002;277:18118-18126. DOI: 10.1074/jbc.M200595200
  23. 23. Nosjean O, Ferro M, Cogé F, Beauverger P, Henlin J-M, Lefoulon F, Fauchère J-L, Delagrange P, Canet E, Boutin JA. Identification of the melatonin-binding site MT3 as the Quinone Reductase 2. The Journal of Biological Chemistry. 2000;275:31311-31317. DOI: 10.1074/jbc.M005141200
  24. 24. Dufourny L, Levasseur A, Migaud M, Callebaut I, Pontarotti P, Malpaux B, Monget P. GPR50 is the mammalian ortholog of Mel1c: Evidence of rapid evolution in mammals. BMC Evolutionary Biology. 2008;8:105. DOI: 10.1186/1471-2148-8-105
  25. 25. Gautier C, Guenin S-P, Riest-Fery I, Perry TJ, Legros C, Nosjean O, Simonneaux V, Grützner F, Boutin JA. Characterization of the Mel1c melatoninergic receptor in platypus (Ornithorhynchus anatinus). PLoS One. 2018;13:e0191904. DOI: 10.1371/journal.pone.0191904
  26. 26. Becker-André M, Wiesenberg I, Schaeren-Wiemers N, André E, Missbach M, Saurat JH, Carlberg C. Pineal gland hormone melatonin binds and activates an orphan of the nuclear receptor superfamily. The Journal of Biological Chemistry. 1994;269:28531-28534
  27. 27. Becker-André M, Wiesenberg I, Schaeren-Wiemers N, André E, Missbach M, Saurat JH, Carlberg C. Pineal gland hormone melatonin binds and activates an orphan of the nuclear receptor superfamily. The Journal of Biological Chemistry. 1997;272:16707
  28. 28. Lardone PJ, Guerrero JM, Fernández-Santos JM, Rubio A, Martín-Lacave I, Carrillo-Vico A. Melatonin synthesized by T lymphocytes as a ligand of the retinoic acid-related orphan receptor. Journal of Pineal Research. 2011;51:454-462. DOI: 10.1111/j.1600-079X.2011.00909.x
  29. 29. Jan JE, Reiter RJ, Wong PKH, Bax MCO, Ribary U, Wasdell MB. Melatonin has membrane receptor-independent hypnotic action on neurons: An hypothesis. Journal of Pineal Research. 2011;50:233-240. DOI: 10.1111/j.1600-079X.2010.00844.x
  30. 30. Reppert SM, Weaver DR, Ebisawa T. Cloning and characterization of a mammalian melatonin receptor that mediates reproductive and circadian responses. Neuron. 1994;13:1177-1185
  31. 31. Weaver DR, Liu C, Reppert SM. Nature's knockout: The Mel1b receptor is not necessary for reproductive and circadian responses to melatonin in Siberian hamsters. Molecular Endocrinology (Baltimore, Md.). 1996;10:1478-1487. DOI: 10.1210/mend.10.11.8923472
  32. 32. Cogé F, Guenin SP, Fery I, Migaud M, Devavry S, Slugocki C, Legros C, Ouvry C, Cohen W, Renault N, Nosjean O, Malpaux B, Delagrange P, Boutin JA. The end of a myth: Cloning and characterization of the ovine melatonin MT(2) receptor. British Journal of Pharmacology. 2009;158:1248-1262. DOI: 10.1111/j.1476-5381.2009.00453.x
  33. 33. Gaildrat P, Becq F, Falcón J. First cloning and functional characterization of a melatonin receptor in fish brain: A novel one? Journal of Pineal Research. 2002;32:74-84
  34. 34. Park Y-J, Park J-G, Kim S-J, Lee Y-D, Saydur Rahman M, Takemura A. Melatonin receptor of a reef fish with lunar-related rhythmicity: Cloning and daily variations. Journal of Pineal Research. 2006;41:166-174. DOI: 10.1111/j.1600-079X.2006.00350.x
  35. 35. Van Kirk T, Powers E, Dowse HB. Melatonin increases the regularity of cardiac rhythmicity in the Drosophila heart in both wild-type and strains bearing pathogenic mutations. Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. 2017;187:63-78. DOI: 10.1007/s00360-016-1019-8
  36. 36. Devavry S, Legros C, Brasseur C, Cohen W, Guenin S-P, Delagrange P, Malpaux B, Ouvry C, Cogé F, Nosjean O, Boutin JA. Molecular pharmacology of the mouse melatonin receptors MT1 and MT2. European Journal of Pharmacology. 2012;677:15-21. DOI: 10.1016/j.ejphar.2011.12.009
  37. 37. Audinot V, Bonnaud A, Grandcolas L, Rodriguez M, Nagel N, Galizzi J-P, Balik A, Messager S, Hazlerigg DG, Barrett P, Delagrange P, Boutin JA. Molecular cloning and pharmacological characterization of rat melatonin MT1 and MT2 receptors. Biochemical Pharmacology. 2008;75:2007-2019. DOI: 10.1016/j.bcp.2008.02.022
  38. 38. Audinot V, Mailliet F, Lahaye-Brasseur C, Bonnaud A, Le Gall A, Amossé C, Dromaint S, Rodriguez M, Nagel N, Galizzi J-P, Malpaux B, Guillaumet G, Lesieur D, Lefoulon F, Renard P, Delagrange P, Boutin JA. New selective ligands of human cloned melatonin MT1 and MT2 receptors. Naunyn-Schmiedeberg's Archives of Pharmacology. 2003;367:553-561. DOI: 10.1007/s00210-003-0751-2
  39. 39. Mor M, Plazzi PV, Spadoni G, Tarzia G. Melatonin. Current Medicinal Chemistry. 1999;6:501-518
  40. 40. Garratt PJ, Tsotinis A. Synthesis of compounds as melatonin agonists and antagonists. Mini Reviews in Medicinal Chemistry. 2007;7:1075-1088
  41. 41. Rivara S, Pala D, Bedini A, Spadoni G. Therapeutic uses of melatonin and melatonin derivatives: A patent review (2012-2014). Expert Opinion on Therapeutic Patents. 2015;25:425-441. DOI: 10.1517/13543776.2014.1001739
  42. 42. Zlotos DP, Jockers R, Cecon E, Rivara S, Witt-Enderby PA. MT 1 and MT 2 melatonin receptors: Ligands, models, oligomers, and therapeutic potential. Journal of Medicinal Chemistry. 2014;57:3161-3185. DOI: 10.1021/jm401343c
  43. 43. Ng KY, Leong MK, Liang H, Paxinos G. Melatonin receptors: Distribution in mammalian brain and their respective putative functions. Brain Structure & Function. 2017;222:2921-2939. DOI: 10.1007/s00429-017-1439-6
  44. 44. Vakkuri O, Lämsä E, Rahkamaa E, Ruotsalainen H, Leppäluoto J. Iodinated melatonin: Preparation and characterization of the molecular structure by mass and 1H NMR spectroscopy. Analytical Biochemistry. 1984;142:284-289
  45. 45. Jockers R, Delagrange P, Dubocovich ML, Markus RP, Renault N, Tosini G, Cecon E, Zlotos DP. Update on melatonin receptors: IUPHAR review 20. British Journal of Pharmacology. 2016;173:2702-2725. DOI: 10.1111/bph.13536
  46. 46. Legros C, Devavry S, Caignard S, Tessier C, Delagrange P, Ouvry C, Boutin JA, Nosjean O. Melatonin MT1 and MT2 receptors display different molecular pharmacologies only in the G-protein coupled state. British Journal of Pharmacology. 2014;171:186-201. DOI: 10.1111/bph.12457
  47. 47. Legros C, Matthey U, Grelak T, Pedragona-Moreau S, Hassler W, Yous S, Thomas E, Suzenet F, Folleas B, Lefoulon F, Berthelot P, Caignard D-H, Guillaumet G, Delagrange P, Brayer J-L, Nosjean O, Boutin JA. New radioligands for describing the molecular pharmacology of MT1 and MT2 melatonin receptors. International Journal of Molecular Sciences. 2013;14:8948-8962. DOI: 10.3390/ijms14058948
  48. 48. Cecon E, Oishi A, Jockers R. Melatonin receptors: Molecular pharmacology and signalling in the context of system bias. British Journal of Pharmacology. DOI: 10.1111/bph.13950
  49. 49. Devavry S, Legros C, Brasseur C, Delagrange P, Spadoni G, Cohen W, Malpaux B, Boutin JA, Nosjean O. Description of the constitutive activity of cloned human melatonin receptors hMT(1) and hMT(2) and discovery of inverse agonists. Journal of Pineal Research. 2012;53:29-37. DOI: 10.1111/j.1600-079X.2011.00968.x
  50. 50. Dupré C, Bruno O, Bonnaud A, Giganti A, Nosjean O, Legros C, Boutin JA. Assessments of cellular melatonin receptor signaling pathways: Β-arrestin recruitment, receptor internalization, and impedance variations. European Journal of Pharmacology. 2018;818:534-544. DOI: 10.1016/j.ejphar.2017.11.022
  51. 51. Boutin JA, Bonnaud A, Brasseur C, Bruno O, Lepretre N, Oosting P, Coumailleau S, Delagrange P, Nosjean O, Legros C. New MT2 melatonin receptor-selective ligands: Agonists and partial agonists. International Journal of Molecular Sciences. 2017;18:e1347. DOI: 10.3390/ijms18071347
  52. 52. Kenakin T. Is the quest for signaling bias worth the effort? Molecular Pharmacology. 2018;93:266-269. DOI: 10.1124/mol.117.111187
  53. 53. Dubocovich ML. Luzindole (N-0774): A novel melatonin receptor antagonist. The Journal of Pharmacology and Experimental Therapeutics. 1988;246:902-910
  54. 54. Dubocovich ML, Masana MI, Iacob S, Sauri DM. Melatonin receptor antagonists that differentiate between the human Mel1a and Mel1b recombinant subtypes are used to assess the pharmacological profile of the rabbit retina ML1 presynaptic heteroreceptor. Naunyn-Schmiedeberg's Archives of Pharmacology. 1997;355:365-375
  55. 55. Yan J-h, Su H-r, Boutin JA, Renard MP, Wang M-w. High-throughput screening assay for new ligands at human melatonin receptors. Acta Pharmacologica Sinica. 2008;29:1515-1521. DOI: 10.1111/j.1745-7254.2008.00903.x
  56. 56. Boutin JA, Lahaye C, Pegurier C, Nicolas JP, Fauchere JL, Langlois M, Renard P, Delagrange P, Canet E. Screening of ligand binding on melatonin receptor using non-peptide combinatorial libraries. Journal of Receptor and Signal Transduction Research. 2000;20:105-118. DOI: 10.3109/10799890009150040
  57. 57. Clement N, Renault N, Guillaume J-L, Cecon E, Journé A-S, Laurent X, Tadagaki K, Cogé F, Gohier A, Delagrange P, Chavatte P, Jockers R. Importance of the second extracellular loop for melatonin MT1 receptor function and absence of melatonin binding in GPR50. British Journal of Pharmacology. 2018; in press. DOI: 10.1111/bph.14029
  58. 58. Gubitz AK, Reppert SM. Chimeric and point-mutated receptors reveal that a single glycine residue in transmembrane domain 6 is critical for high affinity melatonin binding. Endocrinology. 2000;141:1236-1244. DOI: 10.1210/endo.141.3.7356
  59. 59. Kokkola T, Watson MA, White J, Dowell S, Foord SM, Laitinen JT. Mutagenesis of human Mel1a melatonin receptor expressed in yeast reveals domains important for receptor function. Biochemical and Biophysical Research Communications. 1998;249:531-536. DOI: 10.1006/bbrc.1998.9182
  60. 60. Conway S, Mowat ES, Drew JE, Barrett P, Delagrange P, Morgan PJ. Serine residues 110 and 114 are required for agonist binding but not antagonist binding to the melatonin MT(1) receptor. Biochemical and Biophysical Research Communications. 2001;282:1229-1236. DOI: 10.1006/bbrc.2001.4722
  61. 61. Rodbell M. The role of GTP-binding proteins in signal transduction: From the sublimely simple to the conceptually complex. Current Topics in Cellular Regulation. 1992;32:1-47
  62. 62. Bockaert J, Pin JP. Molecular tinkering of G protein-coupled receptors: An evolutionary success. The EMBO Journal. 1999;18:1723-1729. DOI: 10.1093/emboj/18.7.1723
  63. 63. Jones KA, Borowsky B, Tamm JA, Craig DA, Durkin MM, Dai M, Yao WJ, Johnson M, Gunwaldsen C, Huang LY, Tang C, Shen Q, Salon JA, Morse K, Laz T, Smith KE, Nagarathnam D, Noble SA, Branchek TA, Gerald C. GABA(B) receptors function as a heteromeric assembly of the subunits GABA(B)R1 and GABA(B)R2. Nature. 1998;396:674-679. DOI: 10.1038/25348
  64. 64. Hall RA, Premont RT, Chow CW, Blitzer JT, Pitcher JA, Claing A, Stoffel RH, Barak LS, Shenolikar S, Weinman EJ, Grinstein S, Lefkowitz RJ. The beta2-adrenergic receptor interacts with the Na+/H+−exchanger regulatory factor to control Na+/H+ exchange. Nature. 1998;392:626-630. DOI: 10.1038/33458
  65. 65. Boute N, Pernet K, Issad T. Monitoring the activation state of the insulin receptor using bioluminescence resonance energy transfer. Molecular Pharmacology. 2001;60:640-645
  66. 66. Kamal M, Gbahou F, Guillaume J-L, Daulat AM, Benleulmi-Chaachoua A, Luka M, Chen P, Kalbasi Anaraki D, Baroncini M, La Mannoury CC, Millan MJ, Prevot V, Delagrange P, Jockers R. Convergence of melatonin and serotonin (5-HT) signaling at MT2/5-HT2C receptor heteromers. The Journal of Biological Chemistry. 2015;290:11537-11546. DOI: 10.1074/jbc.M114.559542
  67. 67. Ayoub MA, Couturier C, Lucas-Meunier E, Angers S, Fossier P, Bouvier M, Jockers R. Monitoring of ligand-independent dimerization and ligand-induced conformational changes of melatonin receptors in living cells by bioluminescence resonance energy transfer. The Journal of Biological Chemistry. 2002;277:21522-21528. DOI: 10.1074/jbc.M200729200
  68. 68. Levoye A, Dam J, Ayoub MA, Guillaume J-L, Couturier C, Delagrange P, Jockers R. The orphan GPR50 receptor specifically inhibits MT1 melatonin receptor function through heterodimerization. The EMBO Journal. 2006;25:3012-3023. DOI: 10.1038/sj.emboj.7601193
  69. 69. Reppert SM, Weaver DR, Ebisawa T, Mahle CD, Kolakowski LF. Cloning of a melatonin-related receptor from human pituitary. FEBS Letters. 1996;386:219-224
  70. 70. Wojciech S, Ahmad R, Belaid-Choucair Z, Journé A-S, Gallet S, Dam J, Daulat A, Ndiaye-Lobry D, Lahuna O, Karamitri A, Guillaume J-L, Do Cruzeiro M, Guillonneau F, Saade A, Clément N, Courivaud T, Kaabi N, Tadagaki K, Delagrange P, Prévot V, Hermine O, Prunier C, Jockers R. The orphan GPR50 receptor promotes constitutive TGFβ receptor signaling and protects against cancer development. Nature Communications. 2018;9:685. DOI: 10.1038/s41467-018-03609-x
  71. 71. Damian M, Pons V, Renault P, M'Kadmi C, Delort B, Hartmann L, Kaya AI, Louet M, Gagne D, Ben Haj Salah K, Denoyelle S, Ferry G, Boutin JA, Wagner R, Fehrentz J-A, Martinez J, Marie J, Floquet N, Galès C, Mary S, Hamm HE, Banères J-L. GHSR-D2R heteromerization modulates dopamine signaling through an effect on G protein conformation. Proceedings of the National Academy of Sciences of the United States of America. 2018;115:4501-4506. DOI: 10.1073/pnas.1712725115
  72. 72. Pala D, Beuming T, Sherman W, Lodola A, Rivara S, Mor M. Structure-based virtual screening of MT2 melatonin receptor: Influence of template choice and structural refinement. Journal of Chemical Information and Modeling. 2013;53:821-835. DOI: 10.1021/ci4000147
  73. 73. Rivara S, Lorenzi S, Mor M, Plazzi PV, Spadoni G, Bedini A, Tarzia G. Analysis of structure-activity relationships for MT2 selective antagonists by melatonin MT1 and MT2 receptor models. Journal of Medicinal Chemistry. 2005;48:4049-4060. DOI: 10.1021/jm048956y
  74. 74. Pala D, Lodola A, Bedini A, Spadoni G, Rivara S. Homology models of melatonin receptors: Challenges and recent advances. International Journal of Molecular Sciences. 2013;14:8093-8121. DOI: 10.3390/ijms14048093
  75. 75. Logez C, Berger S, Legros C, Banères J-L, Cohen W, Delagrange P, Nosjean O, Boutin JA, Ferry G, Simonin F, Wagner R. Recombinant human melatonin receptor MT1 isolated in mixed detergents shows pharmacology similar to that in mammalian cell membranes. PLoS One. 2014;9:e100616. DOI: 10.1371/journal.pone.0100616
  76. 76. Logez C, Damian M, Legros C, Dupré C, Guéry M, Mary S, Wagner R, M'Kadmi C, Nosjean O, Fould B, Marie J, Fehrentz J-A, Martinez J, Ferry G, Boutin JA, Banères J-L. Detergent-free isolation of functional G protein-coupled receptors into nanometric lipid particles. Biochemistry. 2016;55:38-48. DOI: 10.1021/acs.biochem.5b01040
  77. 77. Hardeland R. Taxon- and site-specific melatonin catabolism. Molecules (Basel, Switzerland). 2017;22:e2015. DOI: 10.3390/molecules22112015
  78. 78. Semak I, Naumova M, Korik E, Terekhovich V, Wortsman J, Slominski A. A novel metabolic pathway of melatonin: Oxidation by cytochrome c. Biochemistry. 2005;44:9300-9307. DOI: 10.1021/bi050202d
  79. 79. Ferry G, Ubeaud C, Lambert P-H, Bertin S, Cogé F, Chomarat P, Delagrange P, Serkiz B, Bouchet J-P, Truscott RJW, Boutin JA. Molecular evidence that melatonin is enzymatically oxidized in a different manner than tryptophan: Investigations with both indoleamine 2,3-dioxygenase and myeloperoxidase. The Biochemical Journal. 2005;388:205-215. DOI: 10.1042/BJ20042075
  80. 80. Niu S, Li F, Tan D-X, Zhang L, Idle JR, Gonzalez FJ, Ma X. Analysis of N1-acetyl-N2-formyl-5-methoxykynuramine/N1-acetyl-5-methoxy-kynuramine formation from melatonin in mice. Journal of Pineal Research. 2010;49:106-114. DOI: 10.1111/j.1600-079x.2010.00771.x
  81. 81. Andersen LPH, Gögenur I, Rosenberg J, Reiter RJ. The safety of melatonin in humans. Clinical Drug Investigation. 2016;36:169-175. DOI: 10.1007/s40261-015-0368-5
  82. 82. Sánchez-Barceló EJ, Mediavilla MD, Tan DX, Reiter RJ. Clinical uses of melatonin: Evaluation of human trials. Current Medicinal Chemistry. 2010;17:2070-2095
  83. 83. Ji Z-Z, Xu Y-C. Melatonin protects podocytes from angiotensin II-induced injury in an in vitro diabetic nephropathy model. Molecular Medicine Reports. 2016;14:920-926. DOI: 10.3892/mmr.2016.5313
  84. 84. Miao Y, Zhou C, Bai Q, Cui Z, ShiYang X, Lu Y, Zhang M, Dai X, Xiong B. The protective role of melatonin in porcine oocyte meiotic failure caused by the exposure to benzo(a)pyrene. Human Reproduction (Oxford, England). 2018;33:116-127. DOI: 10.1093/humrep/dex331
  85. 85. Mehrzadi S, Safa M, Kamrava SK, Darabi R, Hayat P, Motevalian M. Protective mechanisms of melatonin against hydrogen-peroxide-induced toxicity in human bone-marrow-derived mesenchymal stem cells. Canadian Journal of Physiology and Pharmacology. 2017;95:773-786. DOI: 10.1139/cjpp-2016-0409
  86. 86. Sagrillo-Fagundes L, Clabault H, Laurent L, Hudon-Thibeault A-A, Salustiano EMA, Fortier M, Bienvenue-Pariseault J, Wong Yen P, Sanderson JT, Vaillancourt C. Human primary trophoblast cell culture model to study the protective effects of melatonin against hypoxia/reoxygenation-induced disruption. Journal of Visualized Experiments: JoVE. DOI: 10.3791/54228
  87. 87. Xie S, Deng Y, Pan Y-Y, Wang Z-H, Ren J, Guo X-L, Yuan X, Shang J, Liu H-G. Melatonin protects against chronic intermittent hypoxia-induced cardiac hypertrophy by modulating autophagy through the 5′ adenosine monophosphate-activated protein kinase pathway. Biochemical and Biophysical Research Communications. 2015;464:975-981. DOI: 10.1016/j.bbrc.2015.06.149
  88. 88. Boutin JA. Quinone reductase 2 as a promising target of melatonin therapeutic actions. Expert Opinion on Therapeutic Targets. 2015;20:303-317. DOI: 10.1517/14728222.2016.1091882
  89. 89. Goldberg DM, Yan J, Soleas GJ. Absorption of three wine-related polyphenols in three different matrices by healthy subjects. Clinical Biochemistry. 2003;36:79-87
  90. 90. Legros C, Brasseur C, Delagrange P, Ducrot P, Nosjean O, Boutin JA. Alternative radioligands for investigating the molecular pharmacology of melatonin receptors. The Journal of Pharmacology and Experimental Therapeutics. 2016;356:681-692. DOI: 10.1124/jpet.115.229989
  91. 91. Sáenz de Miera C, Sage-Ciocca D, Simonneaux V, Pévet P, Monecke S. Melatonin-independent photoperiodic entrainment of the Circannual TSH rhythm in the pars Tuberalis of the European hamster. Journal of Biological Rhythms. 2018;33(3):302-317. DOI: 10.1177/0748730418766601
  92. 92. Zampol MA, Barros MH. Melatonin improves survival and respiratory activity of yeast cells challenged by alpha-synuclein and menadione. Yeast (Chichester, England). 2018;35:281-290. DOI: 10.1002/yea.3296
  93. 93. Jiao J, Ma Y, Chen S, Liu C, Song Y, Qin Y, Yuan C, Liu Y. Melatonin-producing endophytic bacteria from grapevine roots promote the abiotic stress-induced production of endogenous melatonin in their hosts. Frontiers in Plant Science. 2016;7:1387. DOI: 10.3389/fpls.2016.01387
  94. 94. Díaz-Casado ME, Rusanova I, Aranda P, Fernández-Ortiz M, Sayed RKA, Fernández-Gil BI, Hidalgo-Gutiérrez A, Escames G, López LC, Acuña-Castroviejo D. In vivo determination of mitochondrial respiration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated zebrafish reveals the efficacy of melatonin in restoring mitochondrial normalcy. Zebrafish. 2018;15:15-26. DOI: 10.1089/zeb.2017.1479
  95. 95. Hardeland R. Melatonin in plants - diversity of levels and multiplicity of functions. Frontiers in Plant Science. 2016;7:198. DOI: 10.3389/fpls.2016.00198
  96. 96. Tan D-X, Zheng X, Kong J, Manchester LC, Hardeland R, Kim SJ, Xu X, Reiter RJ. Fundamental issues related to the origin of melatonin and melatonin isomers during evolution: Relation to their biological functions. International Journal of Molecular Sciences. 2014;15:15858-15890. DOI: 10.3390/ijms150915858
  97. 97. Tekbas OF, Ogur R, Korkmaz A, Kilic A, Reiter RJ. Melatonin as an antibiotic: New insights into the actions of this ubiquitous molecule. Journal of Pineal Research. 2008;44:222-226. DOI: 10.1111/j.1600-079X.2007.00516.x
  98. 98. Anderson G, Maes M, Markus RP, Rodriguez M. Ebola virus: Melatonin as a readily available treatment option. Journal of Medical Virology. 2015;87:537-543. DOI: 10.1002/jmv.24130
  99. 99. Roy J, Galano J-M, Durand T, Le Guennec J-Y, Lee JC-Y. Physiological role of reactive oxygen species as promoters of natural defenses. FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology. 2017;31:3729-3745. DOI: 10.1096/fj.201700170R
  100. 100. Abdel Moneim AE, Ortiz F, Leonardo-Mendonca RC, Vergano-Villodres R, Guerrero-Martinez JA, Lopez LC, Acuna-Castroviejo D, Escames G. Protective effects of melatonin against oxidative damage induced by Egyptian cobra (Naja haje) crude venom in rats. Acta Tropica. 2015;143:58-65. DOI: 10.1016/j.actatropica.2014.12.007
  101. 101. Allagui MS, Hachani R, Saidi S, Feriani A, Murat JC, Kacem K, El Feki A. Pleiotropic protective roles of melatonin against aluminium-induced toxicity in rats. General Physiology and Biophysics. 2015;34:415-424. DOI: 10.4149/gpb_2015028
  102. 102. Al-Olayan EM, El-Khadragy MF, Abdel Moneim AE. The protective properties of melatonin against aluminium-induced neuronal injury. International Journal of Experimental Pathology. 2015;96:196-202. DOI: 10.1111/iep.12122
  103. 103. Al-Rasheed N, Faddah L, Al-Rasheed N, Bassiouni YA, Hasan IH, Mahmoud AM, Mohamad RA, Yacoub HI. Protective effects of silymarin, alone or in combination with chlorogenic acid and/or melatonin, against carbon tetrachloride-induced hepatotoxicity. Pharmacognosy Magazine. 2016;12:S337-S345. DOI: 10.4103/0973-1296.185765
  104. 104. Amin AH, El-Missiry MA, Othman AI. Melatonin ameliorates metabolic risk factors, modulates apoptotic proteins, and protects the rat heart against diabetes-induced apoptosis. European Journal of Pharmacology. 2015;747:166-173. DOI: 10.1016/j.ejphar.2014.12.002
  105. 105. Asghari MH, Moloudizargari M, Abdollahi M. In response to the comments on our recently published paper entitled “on the mechanisms of melatonin in protection of aluminum phosphide cardiotoxicity”. Archives of Toxicology. 2017;91:3457-3458. DOI: 10.1007/s00204-017-2029-3
  106. 106. Banaei S, Ahmadiasl N, Alihemmati A. Comparison of the protective effects of erythropoietin and melatonin on renal ischemia-reperfusion injury. Trauma Monthly. 2016;21:e23005. DOI: 10.5812/traumamon.23005
  107. 107. Barberino RS, Menezes VG, Ribeiro AEAS, Palheta RC, Jiang X, Smitz JEJ, Matos MHT. Melatonin protects against cisplatin-induced ovarian damage in mice via the MT1 receptor and antioxidant activity. Biology of Reproduction. 2017;96:1244-1255. DOI: 10.1093/biolre/iox053
  108. 108. Berkiks I, Benmhammed H, Mesfioui A, Ouichou A, El Hasnaoui A, Mouden S, Touil T, Bahbiti Y, Nakache R, El Hessni A. Postnatal melatonin treatment protects against affective disorders induced by early-life immune stimulation by reducing the microglia cell activation and oxidative stress. The International Journal of Neuroscience. 2017:1-10. DOI: 10.1080/00207454.2017.1398156
  109. 109. Cao S, Shrestha S, Li J, Yu X, Chen J, Yan F, Ying G, Gu C, Wang L, Chen G. Melatonin-mediated mitophagy protects against early brain injury after subarachnoid hemorrhage through inhibition of NLRP3 inflammasome activation. Scientific Reports. 2017;7:2417. DOI: 10.1038/s41598-017-02679-z
  110. 110. Cebi Sen C, Yumusak N, Atilgan HI, Sadic M, Koca G, Korkmaz M. The protective effect of melatonin on sperm quality in rat after radioiodine treatment. Andrologia. DOI: 10.1111/and.12962
  111. 111. Chang Y-C, Hsu S-Y, Yang C-C, Sung P-H, Chen Y-L, Huang T-H, Kao G-S, Chen S-Y, Chen K-H, Chiang H-J, Yip H-K, Lee F-Y. Enhanced protection against renal ischemia-reperfusion injury with combined melatonin and exendin-4 in a rodent model. Experimental Biology and Medicine (Maywood, N.J.). 2016;241:1588-1602. DOI: 10.1177/1535370216642528
  112. 112. Chang C-L, Sung P-H, Sun C-K, Chen C-H, Chiang H-J, Huang T-H, Chen Y-L, Zhen Y-Y, Chai H-T, Chung S-Y, Tong M-S, Chang H-W, Chen H-H, Yip H-K. Protective effect of melatonin-supported adipose-derived mesenchymal stem cells against small bowel ischemia-reperfusion injury in rat. Journal of Pineal Research. 2015;59:206-220. DOI: 10.1111/jpi.12251
  113. 113. Chen Y, Zhang J, Zhao Q, Chen Q, Sun Y, Jin Y, Wu J. Melatonin induces anti-inflammatory effects to play a protective role via endoplasmic reticulum stress in acute pancreatitis. Cellular Physiology and Biochemistry: International Journal of Experimental Cellular Physiology, Biochemistry, and Pharmacology. 2016;40:1094-1104. DOI: 10.1159/000453164
  114. 114. Chen K-H, Yang C-H, Wallace CG, Lin C-R, Liu C-K, Yin T-C, Huang T-H, Chen Y-L, Sun C-K, Yip H-K. Combination therapy with extracorporeal shock wave and melatonin markedly attenuated neuropathic pain in rat. American Journal of Translational Research. 2017;9:4593-4606
  115. 115. Czechowska G, Celinski K, Korolczuk A, Wojcicka G, Dudka J, Bojarska A, Reiter RJ. Protective effects of melatonin against thioacetamide-induced liver fibrosis in rats. Journal of Physiology and Pharmacology : An Official Journal of the Polish Physiological Society. 2015;66:567-579
  116. 116. Das N, Mandala A, Naaz S, Giri S, Jain M, Bandyopadhyay D, Reiter RJ, Roy SS. Melatonin protects against lipid-induced mitochondrial dysfunction in hepatocytes and inhibits stellate cell activation during hepatic fibrosis in mice. Journal of Pineal Research. 2017;62:e12404. DOI: 10.1111/jpi.12404
  117. 117. Ding M, Ning J, Feng N, Li Z, Liu Z, Wang Y, Wang Y, Li X, Huo C, Jia X, Xu R, Fu F, Wang X, Pei J. Dynamin-related protein 1-mediated mitochondrial fission contributes to post-traumatic cardiac dysfunction in rats and the protective effect of melatonin. Journal of Pineal Research. 2018;64:e12447. DOI: 10.1111/jpi.12447
  118. 118. Ding K, Xu J, Wang H, Zhang L, Wu Y, Li T. Melatonin protects the brain from apoptosis by enhancement of autophagy after traumatic brain injury in mice. Neurochemistry International. 2015;91:46-54. DOI: 10.1016/j.neuint.2015.10.008
  119. 119. Dos Santos M, Favero G, Bonomini F, Stacchiotti A, Rodella LF, Veronese FV, Rezzani R. Oral supplementation of melatonin protects against lupus nephritis renal injury in a pristane-induced lupus mouse model. Life Sciences. 2018;193:242-251. DOI: 10.1016/j.lfs.2017.10.038
  120. 120. Drąg-Kozak E, Socha M, Gosiewski G, Łuszczek-Trojnar E, Chyb J, Popek W. Protective effect of melatonin on cadmium-induced changes in some maturation and reproductive parameters of female Prussian carp (Carassius gibelio B.). Environmental Science and Pollution Research International. DOI: 10.1007/s11356-018-1308-8
  121. 121. Ewida SF, Al-Sharaky DR. Implication of renal aquaporin-3 in fructose-induced metabolic syndrome and melatonin protection. Journal of Clinical and Diagnostic Research: JCDR. 2016;10:CF06-CF11. DOI: 10.7860/JCDR/2016/18362.7656
  122. 122. Favero G, Trapletti V, Bonomini F, Stacchiotti A, Lavazza A, Rodella LF, Rezzani R. Oral supplementation of melatonin protects against fibromyalgia-related skeletal muscle alterations in reserpine-induced myalgia rats. International Journal of Molecular Sciences. 2017;18:e1389. DOI: 10.3390/ijms18071389
  123. 123. Fernández-Gil B, Moneim AEA, Ortiz F, Shen Y-Q, Soto-Mercado V, Mendivil-Perez M, Guerra-Librero A, Acuña-Castroviejo D, Molina-Navarro MM, García-Verdugo JM, Sayed RKA, Florido J, Luna JD, López LC, Escames G. Melatonin protects rats from radiotherapy-induced small intestine toxicity. PLoS One. 2017;12:e0174474. DOI: 10.1371/journal.pone.0174474
  124. 124. Galley HF, McCormick B, Wilson KL, Lowes DA, Colvin L, Torsney C. Melatonin limits paclitaxel-induced mitochondrial dysfunction in vitro and protects against paclitaxel-induced neuropathic pain in the rat. Journal of Pineal Research. 2017;63:e12444. DOI: 10.1111/jpi.12444
  125. 125. Ghaznavi H, Mehrzadi S, Dormanesh B, Tabatabaei SMTH, Vahedi H, Hosseinzadeh A, Pazoki-Toroudi H, Rashidian A. Comparison of the protective effects of melatonin and silymarin against gentamicin-induced nephrotoxicity in rats. Journal of Evidence-based Complementary & Alternative Medicine. 2016;21:NP49-NP55. DOI: 10.1177/2156587215621672
  126. 126. Ghosh AK, Naaz S, Bhattacharjee B, Ghosal N, Chattopadhyay A, Roy S, Reiter RJ, Bandyopadhyay D. Mechanism of melatonin protection against copper-ascorbate-induced oxidative damage in vitro through isothermal titration calorimetry. Life Sciences. 2017;180:123-136. DOI: 10.1016/j.lfs.2017.05.022
  127. 127. Goc Z, Szaroma W, Kapusta E, Dziubek K. Protective effects of melatonin on the activity of SOD, CAT, GSH-Px and GSH content in organs of mice after administration of SNP. The Chinese Journal of Physiology. 2017;60:1-10. DOI: 10.4077/CJP.2017.BAF435
  128. 128. Goudarzi M, Khodayar MJ, Hosseini Tabatabaei SMT, Ghaznavi H, Fatemi I, Mehrzadi S. Pretreatment with melatonin protects against cyclophosphamide-induced oxidative stress and renal damage in mice. Fundamental & Clinical Pharmacology. 2017;31:625-635. DOI: 10.1111/fcp.12303
  129. 129. Hermoso DAM, Shimada LBC, Gilglioni EH, Constantin J, Mito MS, Hermoso APM, Salgueiro-Pagadigorria CL, Iwamoto ELI. Melatonin protects female rats against steatosis and liver oxidative stress induced by oestrogen deficiency. Life Sciences. 2016;157:178-186. DOI: 10.1016/j.lfs.2016.05.044
  130. 130. Hsu J-T, Le P-H, Lin C-J, Chen T-H, Kuo C-J, Chiang K-C, Yeh T-S. Mechanism of salutary effects of melatonin-mediated liver protection after trauma-hemorrhage: P38 MAPK-dependent iNOS/HIF-1α pathway. American Journal of Physiology. Gastrointestinal and Liver Physiology. 2017;312:G427-G433. DOI: 10.1152/ajpgi.00440.2016
  131. 131. Hu Y, Wang Z, Pan S, Zhang H, Fang M, Jiang H, Zhang H, Gao Z, Xu K, Li Z, Xiao J, Lin Z. Melatonin protects against blood-brain barrier damage by inhibiting the TLR4/ NF-κB signaling pathway after LPS treatment in neonatal rats. Oncotarget. 2017;8:31638-31654. DOI: 10.18632/oncotarget.15780
  132. 132. Ji M-H, Xia D-G, Zhu L-Y, Zhu X, Zhou X-Y, Xia J-Y, Yang J-J. Short- and long-term protective effects of melatonin in a mouse model of sepsis-associated encephalopathy. Inflammation. 2018;41:515-529. DOI: 10.1007/s10753-017-0708-0
  133. 133. Jiang T, Chang Q, Cai J, Fan J, Zhang X, Xu G. Protective effects of melatonin on retinal inflammation and oxidative stress in experimental diabetic retinopathy. Oxidative Medicine and Cellular Longevity. 2016;2016:3528274. DOI: 10.1155/2016/3528274
  134. 134. Jin CJ, Engstler AJ, Sellmann C, Ziegenhardt D, Landmann M, Kanuri G, Lounis H, Schroder M, Vetter W, Bergheim I. Sodium butyrate protects mice from the development of the early signs of non-alcoholic fatty liver disease: Role of melatonin and lipid peroxidation. The British Journal of Nutrition. 2016;116:1682-1693. DOI: 10.1017/S0007114516004025
  135. 135. Karaer I, Simsek G, Gul M, Bahar L, Gurocak S, Parlakpinar H, Nuransoy A. Melatonin protects inner ear against radiation damage in rats. The Laryngoscope. 2015;125:E345-E349. DOI: 10.1002/lary.25376
  136. 136. Karimfar MH, Niazvand F, Haghani K, Ghafourian S, Shirazi R, Bakhtiyari S. The protective effects of melatonin against cryopreservation-induced oxidative stress in human sperm. International Journal of Immunopathology and Pharmacology. 2015;28:69-76. DOI: 10.1177/0394632015572080
  137. 137. Khaksar M, Oryan A, Sayyari M, Rezabakhsh A, Rahbarghazi R. Protective effects of melatonin on long-term administration of fluoxetine in rats. Experimental and Toxicologic Pathology : Official Journal of the Gesellschaft fur Toxikologische Pathologie. 2017;69:564-574. DOI: 10.1016/j.etp.2017.05.002
  138. 138. Khalil WKB, Abdu F. Protective effect of melatonin against zonisamide-induced reproductive disorders in male rats. Archives of Medical Science. AMS. 2015;11:660-669. DOI: 10.5114/aoms.2013.39384
  139. 139. Koc S, Cayli S, Aksakal C, Ocakli S, Soyalic H, Somuk BT, Yuce S. Protective effects of melatonin and selenium against apoptosis of olfactory sensory neurons: A rat model study. American Journal of Rhinology & Allergy. 2016;30:62-66. DOI: 10.2500/ajra.2016.30.4313
  140. 140. Lebda MA, Sadek KM, Abouzed TK, Tohamy HG, El-Sayed YS. Melatonin mitigates thioacetamide-induced hepatic fibrosis via antioxidant activity and modulation of proinflammatory cytokines and fibrogenic genes. Life Sciences. 2018;192:136-143. DOI: 10.1016/j.lfs.2017.11.036
  141. 141. Lee J-H, Moon J-H, Nazim UM, Lee Y-J, Seol J-W, Eo S-K, Lee J-H, Park S-Y. Melatonin protects skin keratinocyte from hydrogen peroxide-mediated cell death via the SIRT1 pathway. Oncotarget. 2016;7:12075-12088. DOI: 10.18632/oncotarget.7679
  142. 142. Li R, Luo X, Li L, Peng Q, Yang Y, Zhao L, Ma M, Hou Z. The protective effects of melatonin against oxidative stress and inflammation induced by acute cadmium exposure in mice testis. Biological Trace Element Research. 2016;170:152-164. DOI: 10.1007/s12011-015-0449-6
  143. 143. Li Y, Zhang Z, He C, Zhu K, Xu Z, Ma T, Tao J, Liu G. Melatonin protects porcine oocyte in vitro maturation from heat stress. Journal of Pineal Research. 2015;59:365-375. DOI: 10.1111/jpi.12268
  144. 144. Lopez A, Ortiz F, Doerrier C, Venegas C, Fernandez-Ortiz M, Aranda P, Diaz-Casado ME, Fernandez-Gil B, Barriocanal-Casado E, Escames G, Lopez LC, Acuna-Castroviejo D. Mitochondrial impairment and melatonin protection in parkinsonian mice do not depend of inducible or neuronal nitric oxide synthases. PLoS One. 2017;12:e0183090. DOI: 10.1371/journal.pone.0183090
  145. 145. Lv Y, Zhang P, Guo J, Zhu Z, Li X, Xu D, Zeng W. Melatonin protects mouse spermatogonial stem cells against hexavalent chromium-induced apoptosis and epigenetic histone modification. Toxicology and Applied Pharmacology. 2018;340:30-38. DOI: 10.1016/j.taap.2017.12.017
  146. 146. Ma Q, Yang J, Huang X, Guo W, Li S, Zhou H, Li J, Cao F, Chen Y. Poly(Lactide-co-Glycolide)-Monomethoxy-poly-(polyethylene glycol) nanoparticles loaded with melatonin protect adipose-derived stem cells transplanted in infarcted heart tissue. Stem cells (Dayton, Ohio). DOI: 10.1002/stem.2777
  147. 147. Ma M, Chen X-Y, Li B, Li X-T. Melatonin protects premature ovarian insufficiency induced by tripterygium glycosides: Role of SIRT1. American Journal of Translational Research. 2017;9:1580-1602
  148. 148. Ma C, Li LX, Zhang Y, Xiang C, Ma T, Ma ZQ, Zhang ZP. Protective and sensitive effects of melatonin combined with adriamycin on ER+ (estrogen receptor) breast cancer. European Journal of Gynaecological Oncology. 2015;36:197-202
  149. 149. Mehrzadi S, Kamrava SK, Dormanesh B, Motevalian M, Hosseinzadeh A, Hosseini Tabatabaei SMT, Ghaznavi H. Melatonin synergistically enhances protective effect of atorvastatin against gentamicin-induced nephrotoxicity in rat kidney. Canadian Journal of Physiology and Pharmacology. 2016;94:265-271. DOI: 10.1139/cjpp-2015-0277
  150. 150. Mirhoseini M, Talebpour Amiri F, Karimpour Malekshah AA, Rezanejad Gatabi Z, Ghaffari E. Protective effects of melatonin on testis histology following acute torsion-detorsion in rats. International Journal of Reproductive Biomedicine (Yazd, Iran). 2017;15:141-146
  151. 151. Montasser AOS, Saleh H, Ahmed-Farid OA, Saad A, Marie M-AS. Protective effects of Balanites aegyptiaca extract, melatonin and Ursodeoxycholic acid against hepatotoxicity induced by methotrexate in male rats. Asian Pacific Journal of Tropical Medicine. 2017;10:557-565. DOI: 10.1016/j.apjtm.2017.06.003
  152. 152. Mukherjee D, Ghosh AK, Dutta M, Mitra E, Mallick S, Saha B, Reiter RJ, Bandyopadhyay D. Mechanisms of isoproterenol-induced cardiac mitochondrial damage: Protective actions of melatonin. Journal of Pineal Research. 2015;58:275-290. DOI: 10.1111/jpi.12213
  153. 153. Munoz MF, Arguelles S, Cano M, Marotta F, Ayala A. Aging and oxidative stress decrease pineal elongation factor 2: In vivo protective effect of melatonin in young rats treated with cumene hydroperoxide. Journal of Cellular Biochemistry. 2017;118:182-190. DOI: 10.1002/jcb.25624
  154. 154. Naseri S, Moghahi SMHN, Mokhtari T, Roghani M, Shirazi AR, Malek F, Rastegar T. Radio-protective effects of melatonin on subventricular zone in irradiated rat: Decrease in apoptosis and upregulation of nestin. Journal of Molecular Neuroscience : MN. 2017;63:198-205. DOI: 10.1007/s12031-017-0970-5
  155. 155. Naskar A, Prabhakar V, Singh R, Dutta D, Mohanakumar KP. Melatonin enhances L-DOPA therapeutic effects, helps to reduce its dose, and protects dopaminergic neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism in mice. Journal of Pineal Research. 2015;58:262-274. DOI: 10.1111/jpi.12212
  156. 156. O’Neal-Moffitt G, Delic V, Bradshaw PC, Olcese J. Prophylactic melatonin significantly reduces Alzheimer’s neuropathology and associated cognitive deficits independent of antioxidant pathways in AβPPswe/PS1 mice. Molecular Neurodegeneration. 2015;10:813. DOI: 10.1186/s13024-015-0027-6
  157. 157. Ortiz F, Acuna-Castroviejo D, Doerrier C, Dayoub JC, Lopez LC, Venegas C, Garcia JA, Lopez A, Volt H, Luna-Sanchez M, Escames G. Melatonin blunts the mitochondrial/NLRP3 connection and protects against radiation-induced oral mucositis. Journal of Pineal Research. 2015;58:34-49. DOI: 10.1111/jpi.12191
  158. 158. Othman AI, Edrees GM, El-Missiry MA, Ali DA, Aboel-Nour M, Dabdoub BR. Melatonin controlled apoptosis and protected the testes and sperm quality against bisphenol A-induced oxidative toxicity. Toxicology and Industrial Health. 2016;32:1537-1549. DOI: 10.1177/0748233714561286
  159. 159. Ozsoy M, Gonul Y, Ozkececi ZT, Bali A, Celep RB, Kocak A, Adali F, Tosun M, Celik S. The protective effect of melatonin on remote organ liver ischemia and reperfusion injury following aortic clamping. Annali Italiani di Chirurgia. 2016;87:271-279
  160. 160. Ozsoy O, Yildirim FB, Ogut E, Kaya Y, Tanriover G, Parlak H, Agar A, Aslan M. Melatonin is protective against 6-hydroxydopamine-induced oxidative stress in a hemiparkinsonian rat model. Free Radical Research. 2015;49:1004-1014. DOI: 10.3109/10715762.2015.1027198
  161. 161. Pal R, Gulati K, Banerjee BD, Ray A. Pharmacological and biochemical studies on the protective effects of melatonin during stress-induced behavioral and immunological changes in relation to oxidative stress in rats. Canadian Journal of Physiology and Pharmacology. 2016;94:296-301. DOI: 10.1139/cjpp-2015-0240
  162. 162. Pang Y-W, Sun Y-Q, Jiang X-L, Huang Z-Q, Zhao S-J, Du W-H, Hao H-S, Zhao X-M, Zhu H-B. Protective effects of melatonin on bovine sperm characteristics and subsequent in vitro embryo development. Molecular Reproduction and Development. 2016;83:993-1002. DOI: 10.1002/mrd.22742
  163. 163. Patino P, Parada E, Farre-Alins V, Molz S, Cacabelos R, Marco-Contelles J, Lopez MG, Tasca CI, Ramos E, Romero A, Egea J. Melatonin protects against oxygen and glucose deprivation by decreasing extracellular glutamate and Nox-derived ROS in rat hippocampal slices. Neurotoxicology. 2016;57:61-68. DOI: 10.1016/j.neuro.2016.09.002
  164. 164. Paul R, Phukan BC, Justin Thenmozhi A, Manivasagam T, Bhattacharya P, Borah A. Melatonin protects against behavioral deficits, dopamine loss and oxidative stress in homocysteine model of Parkinson's disease. Life Sciences. 2018;192:238-245. DOI: 10.1016/j.lfs.2017.11.016
  165. 165. Rajput P, Jangra A, Kwatra M, Mishra A, Lahkar M. Alcohol aggravates stress-induced cognitive deficits and hippocampal neurotoxicity: Protective effect of melatonin. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie. 2017;91:457-466. DOI: 10.1016/j.biopha.2017.04.077
  166. 166. Sadek AS, Khattab RT. The protective role of melatonin on L-arginine-induced acute pancreatitis in adult male albino rats. Folia Morphologica. 2017;76:66-73. DOI: 10.5603/FM.a2016.0029
  167. 167. Sarihan ME, Parlakpinar H, Ciftci O, Yilmaz F, Sagir M, Yilmaz O, Ceker G. Protective effects of melatonin against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced cardiac injury in rats. European Journal of Pharmacology. 2015;762:214-220. DOI: 10.1016/j.ejphar.2015.04.054
  168. 168. Scheuer C, Pommergaard H-C, Rosenberg J, Gogenur I. Dose dependent sun protective effect of topical melatonin: A randomized, placebo-controlled, double-blind study. Journal of Dermatological Science. 2016;84:178-185. DOI: 10.1016/j.jdermsci.2016.08.007
  169. 169. Shahrokhi N, Khaksari M, Nourizad S, Shahrokhi N, Soltani Z, Gholamhosseinian A. Protective effects of an interaction between vagus nerve and melatonin on gastric ischemia/reperfusion: The role of oxidative stress. Iranian Journal of Basic Medical Sciences. 2016;19:72-79
  170. 170. Shang B, Shi H, Wang X, Guo X, Wang N, Wang Y, Dong L. Protective effect of melatonin on myenteric neuron damage in experimental colitis in rats. Fundamental & Clinical Pharmacology. 2016;30:117-127. DOI: 10.1111/fcp.12181
  171. 171. Shao G, Tian Y, Wang H, Liu F, Xie G. Protective effects of melatonin on lipopolysaccharide-induced mastitis in mice. International Immunopharmacology. 2015;29:263-268. DOI: 10.1016/j.intimp.2015.11.011
  172. 172. Shokri S, Kazemi M, Firouzjaei MA, Hemadi M, Moayeri A, Ganjkhani M, Nejatbakhsh R. Melatonin protects testes against lithium-pilocarpine-induced temporal lobe epilepsy in rats: A time course study. Andrologia. 2015;47:343-353. DOI: 10.1111/and.12269
  173. 173. Shokrzadeh M, Chabra A, Naghshvar F, Ahmadi A, Jafarinejhad M, Hasani-Nourian Y. Protective effects of melatonin against cyclophosphamide-induced oxidative lung toxicity in mice. Drug Research. 2015;65:281-286. DOI: 10.1055/s-0034-1371801
  174. 174. Sinha B, Wu Q, Li W, Tu Y, Sirianni AC, Chen Y, Jiang J, Zhang X, Chen W, Zhou S, Reiter RJ, Manning SM, Patel NJ, Aziz-Sultan AM, Inder TE, Friedlander RM, Fu J, Wang X. Protection of melatonin in experimental models of newborn hypoxic-ischemic brain injury through MT1 receptor. Journal of Pineal Research. 2018;64:e12443. DOI: 10.1111/jpi.12443
  175. 175. Tanabe M, Tamura H, Taketani T, Okada M, Lee L, Tamura I, Maekawa R, Asada H, Yamagata Y, Sugino N. Melatonin protects the integrity of granulosa cells by reducing oxidative stress in nuclei, mitochondria, and plasma membranes in mice. The Journal of Reproduction and Development. 2015;61:35-41. DOI: 10.1262/jrd.2014-105
  176. 176. Tang L, Cong Z, Hao S, Li P, Huang H, Shen Y, Li K, Jing H. Protective effect of melatonin on the development of abdominal aortic aneurysm in a rat model. The Journal of Surgical Research. 2017;209:266-278.e1. DOI: 10.1016/j.jss.2016.06.018
  177. 177. Tas U, Ayan M, Sogut E, Kuloglu T, Uysal M, Tanriverdi HI, Senel U, Ozyurt B, Sarsilmaz M. Protective effects of thymoquinone and melatonin on intestinal ischemia-reperfusion injury. Saudi Journal of Gastroenterology : Official Journal of the Saudi Gastroenterology Association. 2015;21:284-289. DOI: 10.4103/1319-3767.166203
  178. 178. Torabi F, Malekzadeh Shafaroudi M, Rezaei N. Combined protective effect of zinc oxide nanoparticles and melatonin on cyclophosphamide-induced toxicity in testicular histology and sperm parameters in adult Wistar rats. International Journal of Reproductive Biomedicine (Yazd, Iran). 2017;15:403-412
  179. 179. Uygur R, Aktas C, Caglar V, Uygur E, Erdogan H, Ozen OA. Protective effects of melatonin against arsenic-induced apoptosis and oxidative stress in rat testes. Toxicology and Industrial Health. 2016;32:848-859. DOI: 10.1177/0748233713512891
  180. 180. Vazan R, Ravingerova T. Protective effect of melatonin against myocardial injury induced by epinephrine. Journal of Physiology and Biochemistry. 2015;71:43-49. DOI: 10.1007/s13105-014-0377-5
  181. 181. Vinod C, Jagota A. Daily NO rhythms in peripheral clocks in aging male Wistar rats: Protective effects of exogenous melatonin. Biogerontology. 2016;17:859-871. DOI: 10.1007/s10522-016-9656-6
  182. 182. Wang Z, Zhou F, Dou Y, Tian X, Liu C, Li H, Shen H, Chen G. Melatonin alleviates intracerebral hemorrhage-induced secondary brain injury in rats via suppressing apoptosis, inflammation, oxidative stress, dna damage, and mitochondria injury. Translational Stroke Research. 2018;9:74-91. DOI: 10.1007/s12975-017-0559-x
  183. 183. Wang Z, Ni L, Wang J, Lu C, Ren M, Han W, Liu C. The protective effect of melatonin on smoke-induced vascular injury in rats and humans: A randomized controlled trial. Journal of Pineal Research. 2016;60:217-227. DOI: 10.1111/jpi.12305
  184. 184. Xue F, Shi C, Chen Q, Hang W, Xia L, Wu Y, Tao SZ, Zhou J, Shi A, Chen J. Melatonin mediates protective effects against kainic acid-induced neuronal death through safeguarding ER stress and mitochondrial disturbance. Frontiers in Molecular Neuroscience. 2017;10:49. DOI: 10.3389/fnmol.2017.00049
  185. 185. Yang S, Tang W, He Y, Wen L, Sun B, Li S. Long non-coding RNA and microRNA-675/let-7a mediates the protective effect of melatonin against early brain injury after subarachnoid hemorrhage via targeting TP53 and neural growth factor. Cell Death & Disease. 2018;9:99. DOI: 10.1038/s41419-017-0155-8
  186. 186. Yi W-J, Kim TS. Melatonin protects mice against stress-induced inflammation through enhancement of M2 macrophage polarization. International Immunopharmacology. 2017;48:146-158. DOI: 10.1016/j.intimp.2017.05.006
  187. 187. Yildirim ME, Badem H, Cakmak M, Yilmaz H, Kosem B, Karatas OF, Bayrak R, Cimentepe E. Melatonin protects kidney against apoptosis induced by acute unilateral ureteral obstruction in rats. Central European Journal of Urology. 2016;69:225-230. DOI: 10.5173/ceju.2016.770
  188. 188. Yu L-M, Di W-C, Dong X, Li Z, Zhang Y, Xue X-D, Xu Y-L, Zhang J, Xiao X, Han J-S, Liu Y, Yang Y, Wang H-S. Melatonin protects diabetic heart against ischemia-reperfusion injury, role of membrane receptor-dependent cGMP-PKG activation. Biochimica et Biophysica Acta. 2018;1864:563-578. DOI: 10.1016/j.bbadis.2017.11.023
  189. 189. Yu Z, Wang T, Lan M, Zang X-W, Li Y-L, Cui X-S, Kim N-H, Sun S-C. Melatonin protects oocytes from MEHP exposure-induced meiosis defects in porcine. Biology of Reproduction. DOI: 10.1093/biolre/iox185
  190. 190. Yu L, Liang H, Dong X, Zhao G, Jin Z, Zhai M, Yang Y, Chen W, Liu J, Yi W, Yang J, Yi D, Duan W, Yu S. Reduced silent information regulator 1 signaling exacerbates myocardial ischemia-reperfusion injury in type 2 diabetic rats and the protective effect of melatonin. Journal of Pineal Research. 2015;59:376-390. DOI: 10.1111/jpi.12269
  191. 191. Yu L, Liang H, Lu Z, Zhao G, Zhai M, Yang Y, Yang J, Yi D, Chen W, Wang X, Duan W, Jin Z, Yu S. Membrane receptor-dependent Notch1/Hes1 activation by melatonin protects against myocardial ischemia-reperfusion injury: In vivo and in vitro studies. Journal of Pineal Research. 2015;59:420-433. DOI: 10.1111/jpi.12272
  192. 192. Zasada K, Karbownik-Lewinska M. Comparison of potential protective effects of melatonin and propylthiouracil against lipid peroxidation caused by nitrobenzene in the thyroid gland. Toxicology and Industrial Health. 2015;31:1195-1201. DOI: 10.1177/0748233713491799
  193. 193. Zhai M, Liu Z, Zhang B, Jing L, Li B, Li K, Chen X, Zhang M, Yu B, Ren K, Yang Y, Yi W, Yang J, Liu J, Yi D, Liang H, Jin Z, Reiter RJ, Duan W, Yu S. Melatonin protects against the pathological cardiac hypertrophy induced by transverse aortic constriction through activating PGC-1beta: In vivo and in vitro studies. Journal of Pineal Research. 2017;63:e12433. DOI: 10.1111/jpi.12433
  194. 194. Zhang M, Dai X, Lu Y, Miao Y, Zhou C, Cui Z, Liu H, Xiong B. Melatonin protects oocyte quality from Bisphenol A-induced deterioration in the mouse. Journal of Pineal Research. 2017;62:e12396. DOI: 10.1111/jpi.12396
  195. 195. Zhang M, Lin J, Wang S, Cheng Z, Hu J, Wang T, Man W, Yin T, Guo W, Gao E, Reiter RJ, Wang H, Sun D. Melatonin protects against diabetic cardiomyopathy through Mst1/Sirt3 signaling. Journal of Pineal Research. 2017;63:e12418. DOI: 10.1111/jpi.12418
  196. 196. Zhang Y, Wei Z, Liu W, Wang J, He X, Huang H, Zhang J, Yang Z. Melatonin protects against arsenic trioxide-induced liver injury by the upregulation of Nrf2 expression through the activation of PI3K/AKT pathway. Oncotarget. 2017;8:3773-3780. DOI: 10.18632/oncotarget.13931
  197. 197. Zhang S, Wang P, Ren L, Hu C, Bi J. Protective effect of melatonin on soluble Abeta1-42-induced memory impairment, astrogliosis, and synaptic dysfunction via the Musashi1/Notch1/Hes1 signaling pathway in the rat hippocampus. Alzheimer's Research & Therapy. 2016;8:40. DOI: 10.1186/s13195-016-0206-x
  198. 198. Zhao J, Fu B, Peng W, Mao T, Wu H, Zhang Y. Melatonin protect the development of preimplantation mouse embryos from sodium fluoride-induced oxidative injury. Environmental Toxicology and Pharmacology. 2017;54:133-141. DOI: 10.1016/j.etap.2017.06.014
  199. 199. Zhou H, Zhang Y, Hu S, Shi C, Zhu P, Ma Q, Jin Q, Cao F, Tian F, Chen Y. Melatonin protects cardiac microvasculature against ischemia/reperfusion injury via suppression of mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis. Journal of Pineal Research. 2017;63:e12413. DOI: 10.1111/jpi.12413
  200. 200. Zhu H, Jin Q, Li Y, Ma Q, Wang J, Li D, Zhou H, Chen Y. Melatonin protected cardiac microvascular endothelial cells against oxidative stress injury via suppression of IP3R-Ca2+c/VDAC-Ca2+m axis by activation of MAPK/ERK signaling pathway. Cell Stress & Chaperones. 2018;23:101-113. DOI: 10.1007/s12192-017-0827-4
  201. 201. Kobylinska A, Reiter RJ, Posmyk MM. Melatonin protects cultured tobacco cells against lead-induced cell death via inhibition of cytochrome c translocation. Frontiers in Plant Science. 2017;8:1560. DOI: 10.3389/fpls.2017.01560
  202. 202. Wang L, Feng C, Zheng X, Guo Y, Zhou F, Shan D, Liu X, Kong J. Plant mitochondria synthesize melatonin and enhance the tolerance of plants to drought stress. Journal of Pineal Research. 2017;63:e12429. DOI: 10.1111/jpi.12429
  203. 203. Xu W, Cai S-Y, Zhang Y, Wang Y, Ahammed GJ, Xia X-J, Shi K, Zhou Y-H, Yu J-Q, Reiter RJ, Zhou J. Melatonin enhances thermotolerance by promoting cellular protein protection in tomato plants. Journal of Pineal Research. 2016;61:457-469. DOI: 10.1111/jpi.12359
  204. 204. Zheng X, Tan DX, Allan AC, Zuo B, Zhao Y, Reiter RJ, Wang L, Wang Z, Guo Y, Zhou J, Shan D, Li Q, Han Z, Kong J. Chloroplastic biosynthesis of melatonin and its involvement in protection of plants from salt stress. Scientific Reports. 2017;7:41236. DOI: 10.1038/srep41236
  205. 205. Baburina Y, Odinokova I, Azarashvili T, Akatov V, Lemasters JJ, Krestinina O. 2′,3'-cyclic nucleotide 3′-phosphodiesterase as a messenger of protection of the mitochondrial function during melatonin treatment in aging. Biochimica et Biophysica Acta. 2017;1859:94-103. DOI: 10.1016/j.bbamem.2016.11.003
  206. 206. Bardak H, Uğuz AC, Bardak Y. Protective effects of melatonin and memantine in human retinal pigment epithelium (ARPE-19) cells against 2-ethylpyridine-induced oxidative stress: Implications for age-related macular degeneration. Cutaneous and Ocular Toxicology. 2018;37:112-120. DOI: 10.1080/15569527.2017.1354218
  207. 207. Charao MF, Baierle M, Gauer B, Goethel G, Fracasso R, Paese K, Brucker N, Moro AM, Bubols GB, Dias BB, Matte US, Guterres SS, Pohlmann AR, Garcia SC. Protective effects of melatonin-loaded lipid-core nanocapsules on paraquat-induced cytotoxicity and genotoxicity in a pulmonary cell line. Mutation Research, Genetic Toxicology and Environmental Mutagenesis. 2015;784-785:1-9. DOI: 10.1016/j.mrgentox.2015.04.006
  208. 208. Chen Y, Qing W, Sun M, Lv L, Guo D, Jiang Y. Melatonin protects hepatocytes against bile acid-induced mitochondrial oxidative stress via the AMPK-SIRT3-SOD2 pathway. Free Radical Research. 2015;49:1275-1284. DOI: 10.3109/10715762.2015.1067806
  209. 209. Fu J, Xia X, Liu Z, Wang Y, Wang Y, Shi Q, Song X, Song E, Song Y. The acute exposure of tetrachloro-p-benzoquinone (a.K.A. chloranil) triggers inflammation and neurological dysfunction via toll-like receptor 4 signaling: The protective role of melatonin preconditioning. Toxicology. 2017;381:39-50. DOI: 10.1016/j.tox.2017.02.015
  210. 210. Gurer-Orhan H, Karaaslan C, Ozcan S, Firuzi O, Tavakkoli M, Saso L, Suzen S. Novel indole-based melatonin analogues: Evaluation of antioxidant activity and protective effect against amyloid beta-induced damage. Bioorganic & Medicinal Chemistry. 2016;24:1658-1664. DOI: 10.1016/j.bmc.2016.02.039
  211. 211. Han L, Wang H, Li L, Li X, Ge J, Reiter RJ, Wang Q. Melatonin protects against maternal obesity-associated oxidative stress and meiotic defects in oocytes via the SIRT3-SOD2-dependent pathway. Journal of Pineal Research. 2017;63:e12431. DOI: 10.1111/jpi.12431
  212. 212. Janjetovic Z, Jarrett SG, Lee EF, Duprey C, Reiter RJ, Slominski AT. Melatonin and its metabolites protect human melanocytes against UVB-induced damage: Involvement of NRF2-mediated pathways. Scientific Reports. 2017;7:1274. DOI: 10.1038/s41598-017-01305-2
  213. 213. Jumnongprakhon P, Govitrapong P, Tocharus C, Pinkaew D, Tocharus J. Melatonin protects methamphetamine-induced Neuroinflammation through NF-kappaB and Nrf2 pathways in Glioma cell line. Neurochemical Research. 2015;40:1448-1456. DOI: 10.1007/s11064-015-1613-2
  214. 214. Liu X-W, Zi Y, Liu Y-E, Zhang Y-B, Xiang L-B, Hou M-x. Melatonin exerts protective effect on N2a cells under hypoxia conditions through Zip1/ERK pathway. Neuroscience Letters. 2015;595:74-80. DOI: 10.1016/j.neulet.2015.04.013
  215. 215. Lu Q, Yi X, Cheng X, Sun X, Yang X. Melatonin protects against myocardial hypertrophy induced by lipopolysaccharide. In Vitro Cellular & Developmental Biology. Animal. 2015;51:353-360. DOI: 10.1007/s11626-014-9844-0
  216. 216. Maarman GJ, Andrew BM, Blackhurst DM, Ojuka EO. Melatonin protects against uric acid-induced mitochondrial dysfunction, oxidative stress, and triglyceride accumulation in C2C12 myotubes. Journal of Applied Physiology (Bethesda, Md. : 1985). 2017;122:1003-1010. DOI: 10.1152/japplphysiol.00873.2016
  217. 217. Ozerkan D, Ozsoy N, Yilmaz E. Vitamin D and melatonin protect the cell's viability and ameliorate the CCl4 induced cytotoxicity in HepG2 and Hep3B hepatoma cell lines. Cytotechnology. 2015;67:995-1002. DOI: 10.1007/s10616-014-9738-8
  218. 218. Pang Y, Zhao S, Sun Y, Jiang X, Hao H, Du W, Zhu H. Protective effects of melatonin on the in vitro developmental competence of bovine oocytes. Animal science journal = Nihon chikusan Gakkaiho. DOI: 10.1111/asj.12970
  219. 219. Sanchez-Bretano A, Baba K, Janjua U, Piano I, Gargini C, Tosini G. Melatonin partially protects 661W cells from H2O2-induced death by inhibiting Fas/FasL-caspase-3. Molecular Vision. 2017;23:844-852
  220. 220. Song J, Kang SM, Lee KM, Lee JE. The protective effect of melatonin on neural stem cell against LPS-induced inflammation. BioMed Research International. 2015;2015:854359. DOI: 10.1155/2015/854359
  221. 221. Tan SS, Han X, Sivakumaran P, Lim SY, Morrison WA. Melatonin protects human adipose-derived stem cells from oxidative stress and cell death. Archives of Plastic Surgery. 2016;43:237-241. DOI: 10.5999/aps.2016.43.3.237
  222. 222. Waseem M, Sahu U, Salman M, Choudhury A, Kar S, Tabassum H, Parvez S, Ghavami S. Melatonin pre-treatment mitigates SHSY-5Y cells against oxaliplatin induced mitochondrial stress and apoptotic cell death. PLoS One. 2017;12:e0180953. DOI: 10.1371/journal.pone.0180953
  223. 223. Wongprayoon P, Govitrapong P. Melatonin protects SH-SY5Y neuronal cells against methamphetamine-induced endoplasmic reticulum stress and apoptotic cell death. Neurotoxicity Research. 2017;31:1-10. DOI: 10.1007/s12640-016-9647-z
  224. 224. Yang F, Yang L, Li Y, Yan G, Feng C, Liu T, Gong R, Yuan Y, Wang N, Idiiatullina E, Bikkuzin T, Pavlov V, Li Y, Dong C, Wang D, Cao Y, Han Z, Zhang L, Huang Q, Ding F, Bi Z, Cai B. Melatonin protects bone marrow mesenchymal stem cells against iron overload-induced aberrant differentiation and senescence. Journal of Pineal Research. 2017;63:e124. DOI: 10.1111/jpi.12422
  225. 225. Yang W, Kang X, Qin N, Li F, Jin X, Ma Z, Qian Z, Wu S. Melatonin protects chondrocytes from impairment induced by glucocorticoids via NAD(+)-dependent SIRT1. Steroids. 2017;126:24-29. DOI: 10.1016/j.steroids.2017.08.005
  226. 226. Yu X, Li Z, Zheng H, Ho J, Chan MTV, Wu WKK. Protective roles of melatonin in central nervous system diseases by regulation of neural stem cells. Cell Proliferation. 2017;50:e12323. DOI: 10.1111/cpr.12323
  227. 227. Zhao Y, Zhao R, Wu J, Wang Q, Pang K, Shi Q, Gao Q, Hu Y, Dong X, Zhang J, Sun J. Melatonin protects against Aβ-induced neurotoxicity in primary neurons via miR-132/PTEN/AKT/FOXO3a pathway. BioFactors (Oxford, England). DOI: 10.1002/biof.1411
  228. 228. Zhou H, Ma Q, Zhu P, Ren J, Reiter RJ, Chen Y. Protective role of melatonin in cardiac ischemia-reperfusion injury: From pathogenesis to targeted therapy. Journal of Pineal Research. 2018;64:e12471. DOI: 10.1111/jpi.12471
  229. 229. Zhu P, Liu J, Shi J, Zhou Q, Liu J, Zhang X, Du Z, Liu Q, Guo Y. Melatonin protects ADSCs from ROS and enhances their therapeutic potency in a rat model of myocardial infarction. Journal of Cellular and Molecular Medicine. 2015;19:2232-2243. DOI: 10.1111/jcmm.12610
  230. 230. Forman HJ, Davies KJA, Ursini F. How do nutritional antioxidants really work: Nucleophilic tone and Para-hormesis versus free radical scavenging in vivo. Free Radical Biology & Medicine. 2014;66:24-35. DOI: 10.1016/j.freeradbiomed.2013.05.045
  231. 231. Forman HJ, Augusto O, Brigelius-Flohe R, Dennery PA, Kalyanaraman B, Ischiropoulos H, Mann GE, Radi R, Roberts LJ, Vina J, Davies KJA. Even free radicals should follow some rules: A guide to free radical research terminology and methodology. Free Radical Biology & Medicine. 2015;78:233-235. DOI: 10.1016/j.freeradbiomed.2014.10.504
  232. 232. Galano A, Castaneda-Arriaga R, Perez-Gonzalez A, Tan D-X, Reiter RJ. Phenolic melatonin-related compounds: Their role as chemical protectors against oxidative stress. Molecules (Basel, Switzerland). DOI: 10.3390/molecules21111442
  233. 233. Cano A, Alcaraz O, Arnao MB. Free radical-scavenging activity of indolic compounds in aqueous and ethanolic media. Analytical and Bioanalytical Chemistry. 2003;376:33-37. DOI: 10.1007/s00216-003-1848-7
  234. 234. Rodriguez C, Mayo JC, Sainz RM, Antolín I, Herrera F, Martín V, Reiter RJ. Regulation of antioxidant enzymes: A significant role for melatonin. Journal of Pineal Research. 2004;36:1-9
  235. 235. Chetsawang B, Putthaprasart C, Phansuwan-Pujito P, Govitrapong P. Melatonin protects against hydrogen peroxide-induced cell death signaling in SH-SY5Y cultured cells: Involvement of nuclear factor kappa B, Bax and Bcl-2. Journal of Pineal Research. 2006;41:116-123. DOI: 10.1111/j.1600-079X.2006.00335.x
  236. 236. Jung KH, Hong S-W, Zheng H-M, Lee D-H, Hong S-S. Melatonin downregulates nuclear erythroid 2-related factor 2 and nuclear factor-kappaB during prevention of oxidative liver injury in a dimethylnitrosamine model. Journal of Pineal Research. 2009;47:173-183. DOI: 10.1111/j.1600-079X.2009.00698.x
  237. 237. Prochaska HJ, Talalay P. Regulatory mechanisms of monofunctional and bifunctional anticarcinogenic enzyme inducers in murine liver. Cancer Research. 1988;48:4776-4782
  238. 238. Liu C, Weaver DR, Jin X, Shearman LP, Pieschl RL, Gribkoff VK, Reppert SM. Molecular dissection of two distinct actions of melatonin on the suprachiasmatic circadian clock. Neuron. 1997;19:91-102
  239. 239. Jin X, von Gall C, Pieschl RL, Gribkoff VK, Stehle JH, Reppert SM, Weaver DR. Targeted disruption of the mouse Mel(1b) melatonin receptor. Molecular and Cellular Biology. 2003;23:1054-1060
  240. 240. O'Neal-Moffitt G, Pilli J, Kumar SS, Olcese J. Genetic deletion of MT₁/MT₂ melatonin receptors enhances murine cognitive and motor performance. Neuroscience. 2014;277:506-521. DOI: 10.1016/j.neuroscience.2014.07.018
  241. 241. Dubocovich ML, Hudson RL, Sumaya IC, Masana MI, Manna E. Effect of MT1 melatonin receptor deletion on melatonin-mediated phase shift of circadian rhythms in the C57BL/6 mouse. Journal of Pineal Research. 2005;39:113-120. DOI: 10.1111/j.1600-079X.2005.00230.x
  242. 242. Hutchinson AJ, Hudson RL, Dubocovich ML. Genetic deletion of MT(1) and MT(2) melatonin receptors differentially abrogates the development and expression of methamphetamine-induced locomotor sensitization during the day and the night in C3H/HeN mice. Journal of Pineal Research. 2012;53:399-409. DOI: 10.1111/j.1600-079X.2012.01010.x
  243. 243. Kleber A, Altmeyer S, Wolf B, Wolf A, Volk T, Fink T, Kubulus D. Impact of melatonin receptor deletion on intracellular signaling in spleen cells of mice after polymicrobial sepsis. Inflammation Research: Official Journal of the European Histamine Research Society. 2014;63:1023-1033. DOI: 10.1007/s00011-014-0779-4
  244. 244. Mühlbauer E, Gross E, Labucay K, Wolgast S, Peschke E. Loss of melatonin signalling and its impact on circadian rhythms in mouse organs regulating blood glucose. European Journal of Pharmacology. 2009;606:61-71. DOI: 10.1016/j.ejphar.2009.01.029
  245. 245. Lardone PJ, Rubio A, Cerrillo I, Gómez-Corvera A, Carrillo-Vico A, Sanchez-Hidalgo M, Guerrero JM, Fernandez-Riejos P, Sanchez-Margalet V, Molinero P. Blocking of melatonin synthesis and MT(1) receptor impairs the activation of Jurkat T cells. Cellular and Molecular Life Sciences: CMLS. 2010;67:3163-3172. DOI: 10.1007/s00018-010-0374-y
  246. 246. Posa L, de Gregorio D, Gobbi G, Comai S. Targeting melatonin MT2 receptors: A novel pharmacological avenue for inflammatory and neuropathic pain. Current Medicinal Chemistry. 2017;24. in press. DOI: 10.2174/0929867324666170209104926
  247. 247. Liu D, Wei N, Man H-Y, Lu Y, Zhu L-Q, Wang J-Z. The MT2 receptor stimulates axonogenesis and enhances synaptic transmission by activating Akt signaling. Cell Death and Differentiation. 2015;22:583-596. DOI: 10.1038/cdd.2014.195
  248. 248. Dubocovich ML. Pharmacology and function of melatonin receptors. FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology. 1988;2:2765-2773
  249. 249. Molinari EJ, North PC, Dubocovich ML. 2-125Iiodo-5-methoxycarbonylamino-N-acetyltryptamine: A selective radioligand for the characterization of melatonin ML2 binding sites. European Journal of Pharmacology. 1996;301:159-168
  250. 250. Paul P, Lahaye C, Delagrange P, Nicolas JP, Canet E, Boutin JA. Characterization of 2-125Iiodomelatonin binding sites in Syrian hamster peripheral organs. The Journal of Pharmacology and Experimental Therapeutics. 1999;290:334-340
  251. 251. Liao S, Dulaney JT, Williams-Ashman HG. Purification and properties of a flavoprotein catalyzing the oxidation of reduced ribosyl nicotinamide. The Journal of Biological Chemistry. 1962;237:2981-2987
  252. 252. Chomarat P, Cogé F, Guénin SP, Mailliet F, Vella F, Mallet C, Giraudet S, Nagel N, Leonce S, Ferry G, Delagrange P, Boutin JA. Cellular knock-down of quinone reductase 2: A laborious road to successful inhibition by RNA interference. Biochimie. 2007;89:1264-1275. DOI: 10.1016/j.biochi.2007.07.004
  253. 253. Mailliet F, Ferry G, Vella F, Thiam K, Delagrange P, Boutin JA. Organs from mice deleted for NRH:Quinone oxidoreductase 2 are deprived of the melatonin binding site MT3. FEBS Letters. 2004;578:116-120. DOI: 10.1016/j.febslet.2004.10.083
  254. 254. Vella F, Ferry G, Delagrange P, Boutin JA. NRH: Quinone reductase 2: An enzyme of surprises and mysteries. Biochemical Pharmacology. 2005;71:1-12. DOI: 10.1016/j.bcp.2005.09.019
  255. 255. Manchester LC, Coto-Montes A, Boga JA, Andersen LPH, Zhou Z, Galano A, Vriend J, Tan D-X, Reiter RJ. Melatonin: An ancient molecule that makes oxygen metabolically tolerable. Journal of Pineal Research. 2015;59:403-419. DOI: 10.1111/jpi.12267
  256. 256. Reiter RJ, Rosales-Corral S, Tan DX, Jou MJ, Galano A, Xu B. Melatonin as a mitochondria-targeted antioxidant: One of evolution's best ideas. Cellular and Molecular Life Sciences: CMLS. 2017;74:3863-3881. DOI: 10.1007/s00018-017-2609-7
  257. 257. Reiter RJ, Tan DX, Rosales-Corral S, Galano A, Zhou XJ, Xu B. Mitochondria: Central organelles for melatonin's antioxidant and anti-aging actions. Molecules (Basel, Switzerland). DOI: 10.3390/molecules23020509
  258. 258. Xu M, Ashraf M. Melatonin protection against lethal myocyte injury induced by doxorubicin as reflected by effects on mitochondrial membrane potential. Journal of Molecular and Cellular Cardiology. 2002;34:75-79. DOI: 10.1006/jmcc.2001.1485
  259. 259. Jou M-J, Peng T-I, Reiter RJ, Jou S-B, Wu H-Y, Wen S-T. Visualization of the antioxidative effects of melatonin at the mitochondrial level during oxidative stress-induced apoptosis of rat brain astrocytes. Journal of Pineal Research. 2004;37:55-70. DOI: 10.1111/j.1600-079X.2004.00140.x
  260. 260. Escames G, López LC, Tapias V, Utrilla P, Reiter RJ, Hitos AB, León J, Rodríguez MI, Acuña-Castroviejo D. Melatonin counteracts inducible mitochondrial nitric oxide synthase-dependent mitochondrial dysfunction in skeletal muscle of septic mice. Journal of Pineal Research. 2006;40:71-78. DOI: 10.1111/j.1600-079X.2005.00281.x
  261. 261. Han Y-x, Zhang S-h, Wang X-m, Wu J-b. Inhibition of mitochondria responsible for the anti-apoptotic effects of melatonin during ischemia-reperfusion. Journal of Zhejiang University. Science. B. 2006;7:142-147. DOI: 10.1631/jzus.2006.B0142
  262. 262. Petrosillo G, Di Venosa N, Pistolese M, Casanova G, Tiravanti E, Colantuono G, Federici A, Paradies G, Ruggiero FM. Protective effect of melatonin against mitochondrial dysfunction associated with cardiac ischemia- reperfusion: Role of cardiolipin. FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology. 2006;20:269-276. DOI: 10.1096/fj.05-4692com
  263. 263. Luchetti F, Canonico B, Mannello F, Masoni C, D'Emilio A, Battistelli M, Papa S, Falcieri E. Melatonin reduces early changes in intramitochondrial cardiolipin during apoptosis in U937 cell line. Toxicology in vitro: An International Journal Published in Association with BIBRA. 2007;21:293-301. DOI: 10.1016/j.tiv.2006.08.003
  264. 264. Jou M-J, Peng T-I, Yu P-Z, Jou S-B, Reiter RJ, Chen J-Y, Wu H-Y, Chen C-C, Hsu L-F. Melatonin protects against common deletion of mitochondrial DNA-augmented mitochondrial oxidative stress and apoptosis. Journal of Pineal Research. 2007;43:389-403. DOI: 10.1111/j.1600-079X.2007.00490.x
  265. 265. Fischer TW, Zmijewski MA, Wortsman J, Slominski A. Melatonin maintains mitochondrial membrane potential and attenuates activation of initiator (casp-9) and effector caspases (casp-3/casp-7) and PARP in UVR-exposed HaCaT keratinocytes. Journal of Pineal Research. 2008;44:397-407. DOI: 10.1111/j.1600-079X.2007.00542.x
  266. 266. Petrosillo G, Fattoretti P, Matera M, Ruggiero FM, Bertoni-Freddari C, Paradies G. Melatonin prevents age-related mitochondrial dysfunction in rat brain via cardiolipin protection. Rejuvenation Research. 2008;11:935-943. DOI: 10.1089/rej.2008.0772
  267. 267. Hibaoui Y, Roulet E, Ruegg UT. Melatonin prevents oxidative stress-mediated mitochondrial permeability transition and death in skeletal muscle cells. Journal of Pineal Research. 2009;47:238-252. DOI: 10.1111/j.1600-079X.2009.00707.x
  268. 268. Jou M-J, Peng T-I, Hsu L-F, Jou S-B, Reiter RJ, Yang C-M, Chiao C-C, Lin Y-F, Chen C-C. Visualization of melatonin's multiple mitochondrial levels of protection against mitochondrial Ca(2+)-mediated permeability transition and beyond in rat brain astrocytes. Journal of Pineal Research. 2010;48:20-38. DOI: 10.1111/j.1600-079X.2009.00721.x
  269. 269. Jou M-J. Melatonin preserves the transient mitochondrial permeability transition for protection during mitochondrial Ca(2+) stress in astrocyte. Journal of Pineal Research. 2011;50:427-435. DOI: 10.1111/j.1600-079X.2011.00861.x
  270. 270. Anjum S, Rahman S, Kaur M, Ahmad F, Rashid H, Ansari RA, Raisuddin S. Melatonin ameliorates bisphenol A-induced biochemical toxicity in testicular mitochondria of mouse. Food and chemical toxicology: An international journal published for the British industrial. Biological Research Association. 2011;49:2849-2854. DOI: 10.1016/j.fct.2011.07.062
  271. 271. Cheshchevik VT, Lapshina EA, Dremza IK, Zabrodskaya SV, Reiter RJ, Prokopchik NI, Zavodnik IB. Rat liver mitochondrial damage under acute or chronic carbon tetrachloride-induced intoxication: Protection by melatonin and cranberry flavonoids. Toxicology and Applied Pharmacology. 2012;261:271-279. DOI: 10.1016/j.taap.2012.04.007
  272. 272. Mukherjee D, Ghosh AK, Bandyopadhyay A, Basu A, Datta S, Pattari SK, Reiter RJ, Bandyopadhyay D. Melatonin protects against isoproterenol-induced alterations in cardiac mitochondrial energy-metabolizing enzymes, apoptotic proteins, and assists in complete recovery from myocardial injury in rats. Journal of Pineal Research. 2012;53:166-179
  273. 273. Yang Y, Duan W, Jin Z, Yi W, Yan J, Zhang S, Wang N, Liang Z, Li Y, Chen W, Yi D, Yu S. JAK2/STAT3 activation by melatonin attenuates the mitochondrial oxidative damage induced by myocardial ischemia/reperfusion injury. Journal of Pineal Research. 2013;55:275-286. DOI: 10.1111/jpi.12070
  274. 274. Canonico B, Luchetti F, Ambrogini P, Arcangeletti M, Betti M, Cesarini E, Lattanzi D, Ciuffoli S, Palma F, Cuppini R, Papa S. Pharmacological doses of melatonin induce alterations in mitochondrial mass and potential, bcl-2 levels and K+ currents in UVB-exposed U937 cells. Cell Biology International. 2013;37:213-226. DOI: 10.1002/cbin.10030
  275. 275. Kashani IR, Rajabi Z, Akbari M, Hassanzadeh G, Mohseni A, Eramsadati MK, Rafiee K, Beyer C, Kipp M, Zendedel A. Protective effects of melatonin against mitochondrial injury in a mouse model of multiple sclerosis. Experimental Brain Research. 2014;232:2835-2846. DOI: 10.1007/s00221-014-3946-5
  276. 276. Guo P, Pi H, Xu S, Zhang L, Li Y, Li M, Cao Z, Tian L, Xie J, Li R, He M, Lu Y, Liu C, Duan W, Yu Z, Zhou Z. Melatonin improves mitochondrial function by promoting MT1/SIRT1/PGC-1 alpha-dependent mitochondrial biogenesis in cadmium-induced hepatotoxicity in vitro. Toxicological Sciences: An Official Journal of the Society of Toxicology. 2014;142:182-195. DOI: 10.1093/toxsci/kfu164
  277. 277. Yang Y, Jiang S, Dong Y, Fan C, Zhao L, Yang X, Li J, Di S, Yue L, Liang G, Reiter RJ, Qu Y. Melatonin prevents cell death and mitochondrial dysfunction via a SIRT1-dependent mechanism during ischemic-stroke in mice. Journal of Pineal Research. 2015;58:61-70. DOI: 10.1111/jpi.12193
  278. 278. He C, Wang J, Zhang Z, Yang M, Li Y, Tian X, Ma T, Tao J, Zhu K, Song Y, Ji P, Liu G. Mitochondria synthesize melatonin to ameliorate its function and improve mice oocyte's quality under in vitro conditions. International Journal of Molecular Sciences. 2016;17:e939. DOI: 10.3390/ijms17060939
  279. 279. Ahluwalia A, Brzozowska IM, Hoa N, Jones MK, Tarnawski AS. Melatonin signaling in mitochondria extends beyond neurons and neuroprotection: Implications for angiogenesis and cardio/gastroprotection. Proceedings of the National Academy of Sciences of the United States of America. 2018;115:E1942-E1943. DOI: 10.1073/pnas.1722131115
  280. 280. Mayo JC, Sainz RM, González-Menéndez P, Hevia D, Cernuda-Cernuda R. Melatonin transport into mitochondria. Cellular and Molecular Life Sciences: CMLS. 2017;74:3927-3940. DOI: 10.1007/s00018-017-2616-8
  281. 281. Gautier C, Dufour E, Dupré C, Lizzo G, Caignard S, Riest-Fery I, Brasseur C, Legros C, Delagrange P, Nosjean O, Simonneaux V, Boutin JA, Guenin SP. Hamster melatonin receptors: Cloning and binding characterization of MT and attempt to clone MT2. International Journal of Medical Sciences. 2018. [In press]

Written By

Jean A. Boutin

Submitted: 13 February 2018 Reviewed: 14 June 2018 Published: 21 November 2018

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Continue reading from the same book

View All
Chapter 3 An Overview of Melatonin as an Antioxidant Molecul...

By Aysun Hacışevki and Burcu Baba

5242 downloads

Chapter 4 Melatonin and Its Indisputable Effects on the Heal...

By Hanan Farouk Aly and Maha Zaki Rizk

1636 downloads

Chapter 5 Melatonin and Exercise: Their Effects on Malondial...

By Mahsa Rastegar Moghaddam Mansouri, Sadegh Abbasian...

1272 downloads