Differential Function of Melatonin MT1 and MT2 Receptors in REM and NREM Sleep

Selective Enhancement of REM Sleep in Male Rats through Activation of Melatonin MT1 Receptors Located in the Locus Ceruleus Norepinephrine Neurons

Sleep disorders affect millions of people around the world and have a high comorbidity with psychiatric disorders. While current hypnotics mostly increase non-rapid eye movement sleep (NREMS), drugs acting selectively on enhancing rapid eye movement sleep (REMS) are lacking. This polysomnographic study in male rats showed that the first-in-class selective melatonin MT1 receptor partial agonist UCM871 increases the duration of REMS without affecting that of NREMS. The REMS-promoting effects of UCM871 occurred by inhibiting, in a dose-response manner, the firing activity of the locus ceruleus (LC) norepinephrine (NE) neurons, which express MT1 receptors. The increase of REMS duration and the inhibition of LC-NE neuronal activity by UCM871 were abolished by MT1 pharmacological antagonism and by an adeno-associated viral (AAV) vector, which selectively knocked down MT1 receptors in the LC-NE neurons. In conclusion, MT1 receptor agonism inhibits LC-NE neurons and triggers REMS, thus representing a novel mechanism and target for REMS disorders and/or psychiatric disorders associated with REMS impairments.

Insomnia in children affected by autism spectrum disorder: The role of melatonin in treatment

The present article explores the connection between insomnia and Autism Spectrum Disorder (ASD), focusing on the efficacy and safety of melatonin treatments as supported by existing research and current guidelines. In this narrative review a group of Italian experts provide an analysis of the various aspects of managing insomnia in children with ASD, highlighting key points that could enhance the quality of life for both patients and their caregivers. This includes the significance of comprehensively understanding the root causes of a child's sleep difficulties for more effective, long-term management. Insomnia, a condition frequently documented in neurodevelopmental disorders such as ASD, greatly affects the lives of patients and caregivers. Recent data show that melatonin-based formulations are effective and safe for treating ASD-related insomnia both short and long term. In particular, prolonged-release melatonin is poised to be the optimal choice for this patient population. This formulation is approved for the treatment of insomnia in children and adolescents aged 2-18 years suffering from ASD and/or Smith-Magenis syndrome, where sleep hygiene measures and behavioral treatments have not been sufficient. In support, emerging research in pediatric settings indicates long-term efficacy and safety, although further research efforts are still needed. Current guidelines recommend managing insomnia and sleep disturbances in ASD using a combination of behavioral and pharmacological methods, primarily melatonin. Recent concerns about accidental melatonin ingestion highlight the need for high purity standards, such as pharmaceutical-grade prolonged-release formulations. The article also summarizes emerging molecular mechanisms from preclinical research, suggesting future therapeutic approaches.

High-dose Agomelatine Combined with Haloperidol Decanoate Improves Cognition, Downregulates MT2, Upregulates D5, and Maintains Krüppel-like Factor 9 But Alters Cardiac Electrophysiology

Haloperidol decanoate (HD) has been implicated in cognitive impairment. Agomelatine (AGO) has been claimed to improve cognition. We aimed at investigating the effects of HD + low- or high-dose AGO on cognition, verifying the melatonergic/dopaminergic to the cholinergic hypothesis of cognition and exploring relevant cardiovascular issues in adult male Wistar albino rats. HD + high-dose AGO prolonged the step-through latency by +61.47% (P < 0.0001), increased the time spent in bright light by +439.49% (P < 0.0001), reduced the time spent in dim light by -66.25% (P < 0.0001), and increased the percent of alternations by +71.25% (P < 0.0001), despite the reductions in brain acetylcholine level by -10.67% (P < 0.0001). Neurodegeneration was minimal, while the mean power frequency of the source wave was reduced by -23.39% (P < 0.05). Concurrently, the relative expression of brain melatonin type 2 receptors was reduced by -18.75% (P < 0.05), against increased expressions of dopamine type 5 receptors by +22.22% (P < 0.0001) and angiopoietin-like 4 by +119.18% (P < 0.0001). Meanwhile, electrocardiogram (ECG) demonstrated inverted P wave, reduced P wave duration by -36.15% (P < 0.0001) and PR interval by -19.91% (P < 0.0001), prolonged RR interval by +27.97% (P < 0.05), increased R wave amplitude by +523.15% (P < 0.0001), and a depressed ST segment and inverted T wave. In rats administered AGO, HD, or HD+ low-dose AGO, Alzheimer's disease (AD)-like neuropathologic features were more evident, accompanied by extensive ECG and neurochemical alterations. HD + high-dose AGO enhances cognition but alters cardiac electrophysiology. SIGNIFICANCE STATEMENT: Given the issue of cognitive impairment associated with HD and the claimed cognitive-enhancing activity of AGO, combined high-dose AGO with HD improved cognition of adult male rats, who exhibited minimal neurodegenerative changes. HD+ high-dose AGO was relatively safe regarding triggering epileptogenesis, while it altered cardiac electrophysiology. In the presence of low acetylcholine, the melatonergic/dopaminergic hypothesis, added to angiopoietin-like 4 and Krüppel-like factor 9, could offer some clue, thus offering novel targets for pharmacologic manipulation of cognition.

Current Aspects of Selected Factors to Modulate Brain Health and Sports Performance in Athletes

This review offers a comprehensive evaluation of current aspects related to nutritional strategies, brain modulation, and muscle recovery, focusing on their applications and the underlying mechanisms of physiological adaptation for promoting a healthy brain, not only in athletes but also for recreationally active and inactive individuals. We propose that applying the rule, among others, of good sleep, regular exercise, and a properly balanced diet, defined as "SPARKS", will have a beneficial effect on the function and regeneration processes of the gut-brain-muscle axis. However, adopting the formula, among others, of poor sleep, stress, overtraining, and dysbiosis, defined as "SMOULDER", will have a detrimental impact on the function of this axis and consequently on human health as well as on athletes. Understanding these dynamics is crucial for optimizing brain health and cognitive function. This review highlights the significance of these factors for overall well-being, suggesting that adopting the "SPARKS" approach may benefit not only athletes but also older adults and individuals with health conditions.

Exercise-with-melatonin therapy improves sleep disorder and motor dysfunction in a rat model of ischemic stroke

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Exercise-with-melatonin therapy has complementary and synergistic effects on spinal cord injury and Alzheimer’s disease, but its effect on stroke is still poorly understood. In this study, we established a rat model of ischemic stroke by occluding the middle cerebral artery for 60 minutes. We treated the rats with exercise and melatonin therapy for 7 consecutive days. Results showed that exercise-with-melatonin therapy significantly prolonged sleep duration in the model rats, increased delta power values, and regularized delta power rhythm. Additionally, exercise-with-melatonin therapy improved coordination, endurance, and grip strength, as well as learning and memory abilities. At the same time, it led to higher hippocampal CA1 neuron activity and postsynaptic density thickness and lower expression of glutamate receptor 2 than did exercise or melatonin therapy alone. These findings suggest that exercise-with-melatonin therapy can alleviate sleep disorder and motor dysfunction by increasing glutamate receptor 2 protein expression and regulating hippocampal CA1 synaptic plasticity.

Melatonin alleviates septic ARDS by inhibiting NCOA4-mediated ferritinophagy in alveolar macrophages

Ferroptosis is a novel form of programmed cell death which can exacerbate lung injury in septic acute respiratory distress syndrome (ARDS). Alveolar macrophages, crucial innate immune cells, play a pivotal role in the pathogenesis of ARDS. Ferritinophagy is a process of ferritin degradation mediated by nuclear receptor coactivator 4 (NCOA4) which releases large amounts of iron ions thus promoting ferroptosis. Recent evidence revealed that inhibiting macrophage ferroptosis can effectively attenuate pulmonary inflammatory injury. Melatonin (MT), an endogenous neurohormone, has antioxidant and anti-inflammatory effects and can reduce septic ARDS. However, it is not clear whether MT's pulmonary protective effect is related to the inhibition of macrophage ferritinophagy. Our in vitro experiments demonstrated that MT decreased intracellular malondialdehyde (MDA), Fe2+, and lipid peroxidation levels, increased glutathione (GSH) levels and cell proliferation, and upregulated glutathione peroxidase 4 (GPX4) and ferritin heavy chain 1 (FTH1) protein levels in LPS-treated macrophages. Mechanistically, the antiferroptotic effect of MT on LPS-treated macrophages was significantly compromised by the overexpression of NCOA4. Our in vivo experiments revealed that MT alleviated the protein expression of NCOA4 and FTH1 in the alveolar macrophages of septic mice. Furthermore, MT improved lipid peroxidation and mitigated damage in alveolar macrophages and lung tissue, ultimately increasing the survival rates of septic mice. These findings indicate that MT can inhibit ferroptosis in an NCOA4-mediated ferritinophagy manner, thereby ameliorating septic ARDS.

Melatonin's effect on hair follicles in a goat (Capra hircus) animal model

Introduction

Melatonin can treat androgenetic alopecia in males. Goats can be used as animal models to study melatonin treatment for human alopecia. In this study, a meta-analysis of melatonin's effects on goat hair follicles was pursued.

Methods

Literature from the last 20 years was searched in Scopus, Science Direct, Web of Science and PubMed. Melatonin's effect on goat hair follicles and litter size were performed through a traditional meta-analysis and trial sequential analysis. A network meta-analysis used data from oocyte development to blastocyst. The hair follicle genes regulated by melatonin performed KEGG and PPI. We hypothesized that there are differences in melatonin receptors between different goats, and therefore completed melatonin receptor 1A homology modelling and molecular docking.

Results

The results showed that melatonin did not affect goat primary follicle or litter size. However, there was a positive correlation with secondary follicle growth. The goat melatonin receptor 1A SNPs influence melatonin's functioning. The wild type gene defect MR1 is a very valuable animal model.

Discussion

Future studies should focus on the relationship between goat SNPs and the effect of embedded melatonin. This study will provide theoretical guidance for the cashmere industry and will be informative for human alopecia research.

Sleep and the sleep electroencephalogram in C57BL/6 and C3H/HeN mice

Different mouse strains used in biomedical research show different phenotypes associated with their genotypes. Two mouse strains commonly used in biomedical sleep research are C57Bl/6 and C3H/He, the strains differ in numerous aspects, including their ability to secrete melatonin as well as the expression of several sleep-related genes. However, sleep regulation has only limitedly been compared between C3H/HeN and C57Bl/6 mice. We therefore compared sleep-wake behaviour and EEG-measured spectral brain activity for C57bl/6 and C3H/HeN mice during a 12:12 h light: dark baseline and during and after a 6 h sleep deprivation. The C3H mice spent more time in NREM sleep around the light-dark transition and more time in REM sleep during the dark phase compared with C57bl/6 mice. The C3H mice also showed more EEG activity in the 4.5-7.5 Hz range during all stages and a stronger 24 h modulation of EEG power density in almost all EEG frequencies during NREM sleep. After the sleep deprivation, C3H mice showed a stronger recovery response, which was expressed in both a larger increase in EEG slow wave activity (SWA) and more time spent in NREM sleep. We show large differences regarding sleep architecture and EEG activity between C3H and C57bl/6 mice. These differences include the amount of waking during the late dark phase, the 24 h amplitude in EEG power density, and the amount of REM sleep during the dark phase. We conclude that differences between mouse strains should be considered when selecting a model strain to improve the generalisability of studies investigating biomedical parameters related to sleep and circadian rhythms.

Acupuncture for primary insomnia: Effectiveness, safety, mechanisms and recommendations for clinical practice

Primary insomnia (PI) is an increasing concern in modern society. Cognitive-behavioral therapy for insomnia is the first-line recommendation, yet limited availability and cost impede its widespread use. While hypnotics are frequently used, balancing their benefits against the risk of adverse events poses challenges. This review summarizes the clinical and preclinical evidence of acupuncture as a treatment for PI, discussing its potential mechanisms and role in reliving insomnia. Clinical trials show that acupuncture improves subjective sleep quality, fatigue, cognitive impairments, and emotional symptoms with minimal adverse events. It also positively impacts objective sleep processes, including prolonging total sleep time, improving sleep efficiency, reducing sleep onset latency and wake after sleep onset, and enhancing sleep architecture/structure, including increasing N3% and REM%, and decreasing N1%. However, methodological shortcomings in some trials diminish the overall quality of evidence. Animal studies suggest that acupuncture restores circadian rhythms in sleep-deprived rodents and improves their performance in behavioral tests, possibly mediated by various clinical variables and pathways. These may involve neurotransmitters, brain-derived neurotrophic factors, inflammatory cytokines, the hypothalamic-pituitary-adrenal axis, gut microbiota, and other cellular events. While the existing findings support acupuncture as a promising therapeutic strategy for PI, additional high-quality trials are required to validate its benefits.

Melatonin regulates the circadian rhythm to ameliorate postoperative sleep disorder and neurobehavioral abnormalities in aged mice

BACKGROUND

Postoperative sleep disorder (PSD) and delirium, which may be associated with surgery and inhalational anesthetics, induce adverse effects in old adults. Emerging evidence indicates that circadian rhythm contributes to various neuropathological diseases, including Alzheimer's disease. Thus, we analyzed the potential role of circadian rhythm in PSD and delirium-like behavior in aged mice and determined whether exogenous melatonin could facilitate entrainment of the circadian rhythm after laparotomy under sevoflurane anesthesia.

METHODS

We selected old C57BL/6J mice which receiving laparotomy/sevoflurane anesthesia as model animals. We employed buried food, open field, and Y maze test to assess delirium-like behavior, and electroencephalography/electromyography (EEG/EMG) were used to investigate sleep changes. We analyzed the transcription rhythm of clock genes in superchiasmatic nucleus (SCN) to explore the effects of surgery and melatonin pretreatment on the circadian rhythm. Then, we measured melatonin receptor levels in SCN and ERK/CREB pathway-related proteins in hippocampus and prefrontal cortex to assess their role in PSDs and delirium-like behavior.

RESULTS

Laparotomy under sevoflurane anesthesia had a greater influence than sevoflurane alone, leading to sleep disorder, a shift in sleep-wake rhythm, and delirium-like behavior. Bmal1, Clock, and Cry1 mRNA expression showed a peak shift, MT1 melatonin receptor expression level was increased in the SCN, and p-ERK/ERK and p-CREB/CREB were decreased in hippocampus and prefrontal cortex of aged mice 1 day after laparotomy. Melatonin showed significant efficacy in ameliorating PSD and delirium-like behavior and restoring the circadian rhythm, reversing melatonin receptor and ERK/CREB pathway expression abnormalities. In addition, most of the beneficial effect of melatonin was antagonized by luzindole, a melatonin receptor antagonist.

CONCLUSIONS

Melatonin receptors in SCN, circadian rhythm, and ERK/CREB signaling pathway participate in the pathophysiological processes of PSD and delirium-like behavior. Melatonin intervention could be a potential preventative approach for PSD and delirium.

Mechanism of GW117 antidepressant action: melatonin receptor-mediated regulation of sleep rhythm

Alterations in circadian sleep patterns constitute a salient manifestation in major depressive disorder. GW117, an emergent antidepressant, functions as an agonist for melatonin 1 and melatonin 2 (MT1/MT2) receptors, in tandem with antagonism of the serotonin (5-HT) 2C receptor. The present investigation is dedicated to elucidating the role and underlying mechanisms by which GW117 ameliorates circadian sleep disruptions. Utilizing an adapted chronic unpredictable mild stress protocol, we induced a depressive-like phenotype and perturbed circadian rhythms in rodent models. Our methodological approach integrated quantitative polymerase chain reaction (qPCR) in real-time, enzyme-linked immunosorbent assay (ELISA), and immunoblotting techniques to probe alterations in the expression of core circadian genes and homeostatic sleep markers. The impact of GW117 was assessed across various dosages (10, 20, and 40 mg/kg) on these molecular signatures. In a parallel examination, we evaluated the influence of GW117 (administered at 15, 40, and 60 mg/kg) on the sleep patterns of healthy mice. The results showed that GW117 significantly improved sleep-wake circadian rhythms, altered sleep architecture, and shortened sleep latency. Furthermore, GW117 increased the expression of several clock genes in the hypothalamus of chronic unpredictable mild stress model rats and normal mice. It also regulated circadian biomarkers, including melatonin and cortisol. Based on our findings, we propose that the beneficial effects of GW117 on sleep rhythms may be due to the melatonin system-mediated activation of the Wnt/β-catenin signaling pathway.

α-Synuclein reduces acetylserotonin O-methyltransferase mediated melatonin biosynthesis by microtubule-associated protein 1 light chain 3 beta-related degradation pathway

Previous studies have demonstrated that α-synuclein (α-SYN) is closely associated with rapid eye movement sleep behavior disorder (RBD) related to several neurodegenerative disorders. However, the exact molecular mechanisms are still rarely investigated. In the present study, we found that in the α-SYNA53T induced RBD-like behavior mouse model, the melatonin level in the plasma and pineal gland were significantly decreased. To elucidate the underlying mechanism of α-SYN-induced melatonin reduction, we investigated the effect of α-SYN in melatonin biosynthesis. Our findings showed that α-SYN reduced the level and activity of melatonin synthesis enzyme acetylserotonin O-methyltransferase (ASMT) in the pineal gland and in the cell cultures. In addition, we found that microtubule-associated protein 1 light chain 3 beta (LC3B) as an important autophagy adapter is involved in the degradation of ASMT. Immunoprecipitation assays revealed that α-SYN increases the binding between LC3B and ASMT, leading to ASMT degradation and a consequent reduction in melatonin biosynthesis. Collectively, our results demonstrate the molecular mechanisms of α-SYN in melatonin biosynthesis, indicating that melatonin is an important molecule involved in the α-SYN-associated RBD-like behaviors, which may provide a potential therapeutic target for RBD of Parkinson's disease.

Therapeutic targets and potential delivery systems of melatonin in osteoarthritis

Osteoarthritis (OA) is a highly prevalent age-related musculoskeletal disorder that typically results in chronic pain and disability. OA is a multifactorial disease, with increased oxidative stress, dysregulated inflammatory response, and impaired matrix metabolism contributing to its onset and progression. The neurohormone melatonin, primarily synthesized by the pineal gland, has emerged as a promising therapeutic agent for OA due to its potential to alleviate inflammation, oxidative stress, and chondrocyte death with minimal adverse effects. The present review provides a comprehensive summary of the current understanding regarding melatonin as a promising pharmaceutical agent for the treatment of OA, along with an exploration of various delivery systems that can be utilized for melatonin administration. These findings may provide novel therapeutic strategies and targets for inhibiting the advancement of OA.

Sex Differences in Sleep Architecture After Traumatic Brain Injury: Potential Implications on Short-Term Episodic Memory and Recovery

Sleep-wake disturbances (SWDs) are common after TBI and often extend into the chronic phase of recovery. Such disturbances in sleep can lead to deficits in executive functioning, attention, and memory consolidation, which may ultimately impact the recovery process. We examined whether SWDs post-TBI were associated with morbidity during the post-acute period. Particular attention was placed on the impact of sleep architecture on learning and memory. Because women are more likely to report SWDs, we examined sex as a biological variable. We also examined subjective quality of life, depression, and disability levels. Data were retrospectively analyzed for 57 TBI patients who underwent an overnight polysomnography. Medical records were reviewed to determine cognitive and functional status during the period of the sleep evaluation. Consideration was given to medications, owing to the fact that a high number of these are likely to have secondary influences on sleep characteristics. Women showed higher levels of disability and reported more depression and lower quality of life. A sex-dependent disruption in sleep architecture was observed, with women having lower percent time in REM sleep. An association between percent time in REM and better episodic memory scores was found. Melatonin utilization had a positive impact on REM duration. Improvements in understanding the impact of sleep-wake disturbances on post-TBI outcome will aid in defining targeted interventions for this population. Findings from this study support the hypothesis that decreases in REM sleep may contribute to chronic disability and underlie the importance of considering sex differences when addressing sleep.

Hypnotic effects of melatonin depend on the environmental lighting conditions in the rat

Acute effects of exogenous melatonin have been widely reported to promote sleep or induce drowsiness in human. However, testing of the hypnotic effects of melatonin in nocturnal rodents has yielded contradictory results. The latter may be associated with differences in concentration, lighting conditions, time of administration of melatonin, and possibly the type of analysis. In this study, electroencephalogram (EEG) and electromyogram were recorded in pigmented male Brown Norway rats under both light-dark (LD) and constant dark (DD) conditions. Melatonin was administered intraperitoneally at a moderate dose of 3 mg/kg, at either 1 h after lights on under LD condition or 1 h after the activity offset under DD condition. The dosage is known to be able to entrain nocturnal rodents in DD conditions, but does not change sleep in rodents in LD. Only the rats under DD conditions showed a significant reduction in nonrapid eye movement (NREM) sleep latency, while the NREM sleep power spectrum remained unaffected. Under LD condition, melatonin did not alter NREM and rapid eye movement (REM) sleep latency, and had only minor effects on the NREM sleep EEG. Regardless of lighting conditions, melatonin administration resulted in less, but longer episodes for all vigilance states suggesting increased vigilance state consolidation. In the discussion, we compare our results with a summary of previously published data concerning the hypnotic effects of melatonin in polysomnographic/EEG-confirmed sleep in humans and nocturnal rodents. In conclusion, the hypnotic effect of exogenous melatonin in nocturnal rodents not only depends on the time of day, and concentration, but is also influenced by the lighting conditions. Regardless of inducing sleep or not, melatonin may consolidate sleep and through that enhance sleep quality.

Evaluating the Protective Effects of Melatonin Against Chronic Iron Administration in Male Wistar Rats: a Comparative Analysis of Affective, Cognitive, and Oxidative Stress with EDTA Chelator

Iron is the dominant metal in the brain and is distributed widely. However, it can lead to various neuropathological and neurobehavioral abnormalities as well as oxidative stress. On the other hand, melatonin, a pineal hormone, is known for its neuroprotective properties, as well as its ability to act as a natural chelator against oxidative stress. It has also been used as an antidepressant and anxiolytic. The study investigated the potential of melatonin and EDTA treatment to prevent anxiety, depressive behavior, and memory impairment in male rats induced by chronic iron administration, and its connection to oxidative stress regulation in the hippocampus and prefrontal cortex. The rats were divided into six groups and intraperitoneally injected for 8 weeks with NaCl solution (control), iron sulfate (1 mg/kg), melatonin (4 mg/kg), EDTA (4 mg/kg), 1 mg/kg of iron + 4 mg/kg of melatonin, or 1 mg/kg of iron + 4 mg/kg of EDTA. In this study, we performed a neurobehavioral assessment and biochemical determinations of oxidative stress levels in the hippocampus and prefrontal cortex of each animal. The results indicate that chronic exposure to iron sulfate induced anxiety-like depressive behavior, and cognitive impairment also increased the levels of lipid peroxidation and nitric oxide, and reduced the activity of catalase in the hippocampus and prefrontal cortex in male Wistar rats, suggesting the induction of oxidative stress. In contrast, these alterations were reversed by melatonin better than EDTA. The results of this study show that melatonin protects against the neurobehavioral changes caused by iron, which may be associated with decreasing oxidative stress in the hippocampus and prefrontal cortex.

The relationship between anesthesia and melatonin: a review

Introduction: This comprehensive review delves into the intricate and multifaceted relationship between anesthesia and melatonin, aiming to provide essential insights for perioperative clinical anesthesiologists and stimulate interest in related research. Anesthesia and surgery have the potential to disrupt melatonin secretion, leading to sleep disorders, postoperative neurocognitive dysfunction and other symptoms. In comparison to previous reviews, this review provides a comprehensive summary of the various aspects linking melatonin and anesthesia, going beyond isolated perspectives. It explores the potential benefits of administering melatonin during the perioperative period, including alleviating anxiety, reducing pain, enhancing perioperative sleep quality, as well as demonstrating immunomodulatory and anti-tumor effects, potentially offering significant advantages for cancer surgery patients. Recent Findings: Anesthesia and surgery have a significant impact on melatonin secretion, the hormone crucial for maintaining circadian rhythms. These procedures disrupt the normal secretion of melatonin, leading to various adverse effects such as sleep disturbances, pain, and postoperative neurocognitive dysfunction. However, the administration of exogenous melatonin during the perioperative period has yielded promising results. It has been observed that perioperative melatonin supplementation can effectively reduce anxiety levels, improve pain management, enhance the quality of perioperative sleep, and potentially decrease the occurrence of postoperative delirium. In recent years, studies have found that melatonin has the potential to improve immune function and exhibit anti-cancer effects, further underscoring its potential advantages for patients undergoing cancer surgery. Summary: In summary, melatonin can serve as an adjuvant drug for anesthesia during the perioperative period. Its administration has demonstrated numerous positive effects, including anti-anxiety properties, sedation, analgesia, improved postoperative sleep, and the potential to reduce the incidence of postoperative delirium. Furthermore, its immune-modulating and anti-tumor effects make it particularly valuable for cancer surgery patients. However, further studies are required to determine the optimal dosage, long-term safety, and potential adverse reactions associated with melatonin administration.

Using pharmacotherapy to address sleep disturbances in autism spectrum disorders

INTRODUCTION

Sleep disorders are the second most common medical comorbidity in autism spectrum disorder (ASD), with effects on daytime behavior and functioning, mood and anxiety, and autism core features. In children with ASD, insomnia also has a negative impact on the whole family's quality of life. Therefore, treatment of sleep disturbances should be considered as a primary goal in the management of ASD patients, and it is important to clarify the scientific evidence to inappropriate treatments.

AREAS COVERED

The authors review the current literature concerning the pharmacological treatment options for the management of sleep-related disorders in patients with ASD (aged 0-18 years) using the PubMed and Cochrane Library databases with the search terms: autism, autistic, autism spectrum disorder, ASD, drug, drug therapy, drug intervention, drug treatment, pharmacotherapy, pharmacological treatment, pharmacological therapy, pharmacological intervention, sleep, sleep disturbance, and sleep disorder.

EXPERT OPINION

Currently, clinicians tend to select medications for the treatment of sleep disorders in ASD based on the first-hand experience of psychiatrists and pediatricians as well as expert opinion. Nevertheless, at the present time, the only compound for which there is sufficient evidence is melatonin, although antihistamines, trazodone, clonidine, ramelteon, gabapentin, or suvorexant can also be considered for selection.

Effects of astaxanthin on depressive and sleep symptoms: A narrative mini-review

Major depressive disorder (MDD) is a prevalent psychiatric condition that results in persistent feelings of sadness and loss of interest, imposing a significant economic burden on health systems and society. Impaired sleep is both a symptom and a risk factor for depression. Natural astaxanthin (AST), a carotenoid primarily derived from algae and aquatic animals, possesses multiple pharmacological properties such as anti-inflammatory, anti-apoptotic, and antioxidant stress effects. Prior research suggests that AST may have antidepressant properties. This mini-review highlights the potential mechanisms by which AST can prevent depression, providing novel insights into drug research for depression treatment. Specifically, this mechanism suggests that astaxanthin may improve sleep and thus potentially aid in the treatment of depression.

Pistacia vera Extract Potentiates the Effect of Melatonin on Human Melatonin MT1 and MT2 Receptors with Functional Selectivity

Melatonin is a tryptophan derivative synthesized in plants and animals. In humans, melatonin acts on melatonin MT₁ and MT₂ receptors belonging to the G protein-coupled receptor (GPCR) family. Synthetic melatonin receptor agonists are prescribed for insomnia and depressive and circadian-related disorders. Here, we tested 25 commercial plant extracts, reported to have beneficial properties in sleep disorders and anxiety, using cellular assays (2─[¹²⁵I]iodomelatonin binding, cAMP inhibition, ERK1/2 activation and β-arrestin2 recruitment) in mock-transfected and HEK293 cells expressing MT₁ or MT₂. Various melatonin receptor-dependent and -independent effects were observed. Extract 18 (Ex18) from Pistacia vera dried fruits stood out with very potent effects in melatonin receptor expressing cells. The high content of endogenous melatonin in Ex18 (5.28 ± 0.46 mg/g extract) is consistent with this observation. Ex18 contains an additional active principle that potentiates the effect of melatonin on G_i protein-dependent pathways but not on β-arrestin2 recruitment. Further active principles potentiating exogenous melatonin were detected in several extracts. In conclusion, we identified plant extracts with various effects in GPCR-based binding and signalling assays and identified high melatonin levels and a melatonin-potentiating activity in Pistacia vera dried fruit extracts that might be of therapeutic potential.

Melatonin-related dysfunction in chronic restraint stress triggers sleep disorders in mice

Stress may trigger sleep disorders and are also risk factors for depression. The study explored the melatonin-related mechanisms of stress-associated sleep disorders on a mouse model of chronic stress by exploring the alteration in sleep architecture, melatonin, and related small molecule levels, transcription and expression of melatonin-related genes as well as proteins. Mice undergoing chronic restraint stress modeling for 28 days showed body weight loss and reduced locomotor activity. Sleep fragmentation, circadian rhythm disorders, and insomnia exhibited in CRS-treated mice formed sleep disorders. Tryptophan and 5-hydroxytryptamine levels were increased in the hypothalamus, while melatonin level was decreased. The transcription and expression of melatonin receptors were reduced, and circadian rhythm related genes were altered. Expression of downstream effectors to melatonin receptors was also affected. These results identified sleep disorders in a mice model of chronic stress. The alteration of melatonin-related pathways was shown to trigger sleep disorders.

Melatonin use in children and adolescents: A scoping review of caregiver perspectives

Despite melatonin's popularity as a pediatric sleep-aid, little has been investigated around caregivers' understanding and perception of melatonin use for their dependent. This scoping review analyzes the current literature on pediatric melatonin use, to understand how caregivers' perceptions around melatonin are shaped by their illness/medication-related beliefs, treatment experience and preferences. A literature search was conducted across Embase, Medline, PsycINFO, PubMed and Scopus, generating 184 results for screening against the inclusion criteria. Nineteen studies were retrieved, comprising of 1561 children and adolescents, aged 8.7 ± 2.3 years (range: 0-44 years), conducted primarily in the United States of America (n = 6), Canada (n = 3) and the Netherlands (n = 3). Studies were evaluated for their study design and caregiver-centered outcomes, encompassing: 1) illness/treatment-related beliefs, 2) treatment satisfaction/effectiveness, 3) treatment preference/acceptability, and 4) impact of child's sleep disturbance on caregivers' quality-of-life. Sleep disturbances necessitating melatonin use occurred alongside congenital/neurodevelopmental comorbidities in 18 studies (95%). Melatonin was commonly associated with "naturalness" and "safety". Concepts of treatment satisfaction versus effectiveness were minimally differentiated within included studies. Caregivers preferred concurrent use of melatonin and behavioral interventions for management of their dependents' sleep. Improved sleep in the dependent generally led to better quality-of-life for caregivers and their family.

Age-Related Effects of Exogenous Melatonin on Anxiety-like Behavior in C57/B6J Mice

The synthesis of melatonin (MLT) physiologically decreases during aging. Treatment with MLT has shown anxiolytic, hypnotic, and analgesic effects, but little is known about possible age-dependent differences in its efficacy. Therefore, we studied the effects of MLT (20 mg/kg, intraperitoneal) on anxiety-like behavior (open field (OFT), elevated plus maze (EPMT), three-chamber sociability, and marble-burying (MBT) tests), and the medial prefrontal cortex (mPFC)-dorsal hippocampus (dHippo) circuit in adolescent (35-40 days old) and adult (three-five months old) C57BL/6 male mice. MLT did not show any effect in adolescents in the OFT and EPMT. In adults, compared to vehicles, it decreased locomotor activity and time spent in the center of the arena in the OFT and time spent in the open arms in the EPMT. In the MBT, no MLT effects were observed in both age groups. In the three-chamber sociability test, MLT decreased sociability and social novelty in adults, while it increased sociability in adolescents. Using local field potential recordings, we found higher mPFC-dHippo synchronization in the delta and low-theta frequency ranges in adults but not in adolescents after MLT treatment. Here, we show age-dependent differences in the effects of MLT in anxiety paradigms and in the modulation of the mPFC-dHippo circuit, indicating that when investigating the pharmacology of the MLT system, age can significantly impact the study outcomes.

Parkinson's Disease: A Narrative Review on Potential Molecular Mechanisms of Sleep Disturbances, REM Behavior Disorder, and Melatonin

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. There is a wide range of sleep disturbances in patients with PD, such as insomnia and rapid eye movement (REM) sleep behavior disorder (or REM behavior disorder (RBD)). RBD is a sleep disorder in which a patient acts out his/her dreams and includes abnormal behaviors during the REM phase of sleep. On the other hand, melatonin is the principal hormone that is secreted by the pineal gland and significantly modulates the circadian clock and mood state. Furthermore, melatonin has a wide range of regulatory effects and is a safe treatment for sleep disturbances such as RBD in PD. However, the molecular mechanisms of melatonin involved in the treatment or control of RBD are unknown. In this study, we reviewed the pathophysiology of PD and sleep disturbances, including RBD. We also discussed the potential molecular mechanisms of melatonin involved in its therapeutic effect. It was concluded that disruption of crucial neurotransmitter systems that mediate sleep, including norepinephrine, serotonin, dopamine, and GABA, and important neurotransmitter systems that mediate the REM phase, including acetylcholine, serotonin, and norepinephrine, are significantly involved in the induction of sleep disturbances, including RBD in PD. It was also concluded that accumulation of α-synuclein in sleep-related brain regions can disrupt sleep processes and the circadian rhythm. We suggested that new treatment strategies for sleep disturbances in PD may focus on the modulation of α-synuclein aggregation or expression.

Sleep disturbances in autism spectrum disorder: Animal models, neural mechanisms, and therapeutics

Sleep is crucial for brain development. Sleep disturbances are prevalent in children with autism spectrum disorder (ASD). Strikingly, these sleep problems are positively correlated with the severity of ASD core symptoms such as deficits in social skills and stereotypic behavior, indicating that sleep problems and the behavioral characteristics of ASD may be related. In this review, we will discuss sleep disturbances in children with ASD and highlight mouse models to study sleep disturbances and behavioral phenotypes in ASD. In addition, we will review neuromodulators controlling sleep and wakefulness and how these neuromodulatory systems are disrupted in animal models and patients with ASD. Lastly, we will address how the therapeutic interventions for patients with ASD improve various aspects of sleep. Together, gaining mechanistic insights into the neural mechanisms underlying sleep disturbances in children with ASD will help us to develop better therapeutic interventions.

Kynurenine aminotransferase II inhibition promotes sleep and rescues impairments induced by neurodevelopmental insult

Dysregulated sleep is commonly reported in individuals with neuropsychiatric disorders, including schizophrenia (SCZ) and bipolar disorder (BPD). Physiology and pathogenesis of these disorders points to aberrant metabolism, during neurodevelopment and adulthood, of tryptophan via the kynurenine pathway (KP). Kynurenic acid (KYNA), a neuroactive KP metabolite derived from its precursor kynurenine by kynurenine aminotransferase II (KAT II), is increased in the brains of individuals with SCZ and BPD. We hypothesize that elevated KYNA, an inhibitor of glutamatergic and cholinergic neurotransmission, contributes to sleep dysfunction. Employing the embryonic kynurenine (EKyn) paradigm to elevate fetal brain KYNA, we presently examined pharmacological inhibition of KAT II to reduce KYNA in adulthood to improve sleep quality. Pregnant Wistar rats were fed either kynurenine (100 mg/day)(EKyn) or control (ECon) diet from embryonic day (ED) 15 to ED 22. Adult male (N = 24) and female (N = 23) offspring were implanted with devices to record electroencephalogram (EEG) and electromyogram (EMG) telemetrically for sleep-wake data acquisition. Each subject was treated with either vehicle or PF-04859989 (30 mg/kg, s.c.), an irreversible KAT II inhibitor, at zeitgeber time (ZT) 0 or ZT 12. KAT II inhibitor improved sleep architecture maintaining entrainment of the light-dark cycle; ZT 0 treatment with PF-04859989 induced transient improvements in rapid eye movement (REM) and non-REM (NREM) sleep during the immediate light phase, while the impact of ZT 12 treatment was delayed until the subsequent light phase. PF-04859989 administration at ZT 0 enhanced NREM delta spectral power and reduced activity and body temperature. In conclusion, reducing de novo KYNA production alleviated sleep disturbances and increased sleep quality in EKyn, while also improving sleep outcomes in ECon offspring. Our findings place attention on KAT II inhibition as a novel mechanistic approach to treating disrupted sleep behavior with potential translational implications for patients with neurodevelopmental and neuropsychiatric disorders.

Melatonin-mediated FKBP4 downregulation protects against stress-induced neuronal mitochondria dysfunctions by blocking nuclear translocation of GR

The physiological crosstalk between glucocorticoid and melatonin maintains neuronal homeostasis in regulating circadian rhythms. However, the stress-inducing level of glucocorticoid triggers mitochondrial dysfunction including defective mitophagy by increasing the activity of glucocorticoid receptors (GRs), leading to neuronal cell death. Melatonin then suppresses glucocorticoid-induced stress-responsive neurodegeneration; however, the regulatory mechanism of melatonin, i.e., associated proteins involved in GR activity, has not been elucidated. Therefore, we investigated how melatonin regulates chaperone proteins related to GR trafficking into the nucleus to suppress glucocorticoid action. In this study, the effects of glucocorticoid on suppressing NIX-mediated mitophagy, followed by mitochondrial dysfunction, neuronal cell apoptosis, and cognitive deficits were reversed by melatonin treatment by inhibiting the nuclear translocation of GRs in both SH-SY5Y cells and mouse hippocampal tissue. Moreover, melatonin selectively suppressed the expression of FKBP prolyl isomerase 4 (FKBP4), which is a co-chaperone protein that works with dynein, to reduce the nuclear translocation of GRs among the chaperone proteins and nuclear trafficking proteins. In both cells and hippocampal tissue, melatonin upregulated melatonin receptor 1 (MT1) bound to Gαq, which triggered the phosphorylation of ERK1. The activated ERK then enhanced DNA methyltransferase 1 (DNMT1)-mediated hypermethylation of FKBP52 promoter, reducing GR-mediated mitochondrial dysfunction and cell apoptosis, the effects of which were reversed by knocking down DNMT1. Taken together, melatonin has a protective effect against glucocorticoid-induced defective mitophagy and neurodegeneration by enhancing DNMT1-mediated FKBP4 downregulation that reduced the nuclear translocation of GRs.

Photoperiod-driven concurrent changes in hypothalamic and brainstem transcription of sleep and immune genes in migratory redheaded bunting

The molecular regulation of sleep in avian migrants is still obscure. We thus investigated this in migratory redheaded buntings, where four life-history states (LHS; i.e. non-migratory, pre-migratory, migratory and refractory states) were induced. There was increased night-time activity (i.e. Zugunruhe) during the migratory state with reduced daytime activity. The recordings of the sleep-wake cycle in buntings showed increased night-time active wakefulness coupled with drastically reduced front and back sleep during migratory phase. Interestingly, we found the buntings to feed and drink even after lights-off during migration. Gene expression studies revealed increased hypothalamic expression of glucocorticoid receptor (nr3c1), and pro-inflammatory cytokines (il1b and il6) in pre-migratory and migratory states, respectively, whereas in brainstem Ca2+/calmodulin-dependent protein kinase 2 (camk2) was upregulated during the migratory state. This suggested a heightened pro-inflammatory state during migration which is a feature of chronic sleep loss, and a possible role of Ca2+ signalling in promoting wakefulness. In both the hypothalamus and brainstem, the expression of melatonin receptors (mel1a and mel1b) was increased in the pre-migratory state, and growth hormone-releasing hormone (ghrh, known to induce sleep) was reduced during the migratory state. The current results demonstrate key molecules involved in the regulation of sleep-wake cycle across LHS in migratory songbirds.

Molecular basis of ligand selectivity for melatonin receptors

Sleep disorders in adults are related to adverse health effects such as reduced quality of life and increased mortality. About 30-40% of adults are suffering from different sleep disorders. The human melatonin receptors (MT1 and MT2) are family A G protein-coupled receptors that respond to the neurohormone melatonin MEL which regulates circadian rhythm and sleep. Many efforts have been made to develop drugs targeting melatonin receptors to treat insomnia, circadian rhythm disorders, and even cancer. However, designing subtype-selective melatonergic drugs remains challenging due to their high similarities in both sequences and structures. MEL (a function-selective compound with a bulky β-naphthyl group) behaves as an MT2-selective antagonist, whereas it is an agonist of MT1. Here, molecular dynamics simulations were used to investigate the ligand selectivity of MT receptors at the atomic level. We found that the binding conformation of MEL differs in different melatonin receptors. In MT1, the naphthalene ring of MEL forms a structure perpendicular to the membrane surface. In contrast, there is a 130° angle between the naphthalene ring of MEL and the membrane surface in MT2. Because of this conformational difference, the MEL leads to a constant water channel in MT1 which activates the receptor. However, MEL hinders the formation of continuous water channels, resulting in an inactive state of MT2. Furthermore, we found that A117^3.29 in MT2 is a crucial amino acid capable of hindering the conformational flip of the MEL molecule. These results, coupled with previous functional data, reveal that although MT1 and MT2 share highly similar orthosteric ligand-binding pockets, they also display distinctive features that could be used to design selective compounds. Our findings provide new insights into functionally selective melatonergic drug development for sleep disorders.

Current Insights into the Risks of Using Melatonin as a Treatment for Sleep Disorders in Older Adults

Exogenous melatonin is commonly used for sleep disorders in older adults, and its use is increasing over time. It appears to have modest efficacy in treating insomnia and circadian rhythm sleep-wake disorders. Melatonin is commonly perceived to be a safe alternative to other hypnotics and is available without prescription in some jurisdictions. New evidence suggests that endogenous melatonin has pleomorphic effects on multiple organ systems, many of which are poorly understood. This narrative review summarizes the current evidence regarding the safety of melatonin in older adults (defined by age over 65 years). Melatonin appears to have a favorable safety profile in this population, however there is a dearth of evidence regarding the safety of prolonged use. There are several factors which increase the risk of adverse effects of melatonin in older adults, and these should be taken into consideration when prescribing to this population.

A randomized, double-blind, placebo-controlled, cross-over pilot study to investigate the efficacy of Rest-ZZZ formula in healthy participants with occasional sleeplessness

The purpose of this study was to investigate the safety and efficacy of Rest-ZZZ, a natural sleep supplement, in healthy adults without a diagnosed sleep disorder. This randomized, double-blind, placebo-controlled, cross-over study consisted of three 7-day supplementation periods with either Rest-ZZZ, Diphenhydramine (DPH), or Placebo, with a 7-day washout. Twenty-seven participants were randomized to one of three intervention sequences and the Healthy People Sleep Quality Index (HPSQI), Quality of Life (QoL), and Profile of Mood States (POMS) questionnaires were assessed at the beginning and end of each supplementation period. Rest-ZZZ and Placebo showed improvements in sleep-related QoL (p ≤ 0.044) and total mood disturbance (TMD) (p =  ≤ 0.028). Fatigue-Inertia was reduced by all study products (p ≤ 0.031). DPH did not result in any significant improvements on sleep quality parameters. A subgroup analysis of participants ≤ 45 years found enhanced efficacy of Rest-ZZZ and improvement in sleep-related QoL vs. Placebo (p = 0.007), as well as improvements in sleep duration (p = 0.007), sleep debt (p = 0.011), and sleep-related QoL (p = 0.033). DPH supplementation resulted in significant improvement in only sleep debt (p = 0.038). Rest-ZZZ had a safe hematology and chemistry profile. Rest-ZZZ resulted in restful sleep that generated corresponding improvements in sleep-related QoL and overall mood. Rest-ZZZ is an efficacious sleep supplement with a favorable safety profile, particularly in those aged 25-45 years.

Circadian medicine for aging attenuation and sleep disorders: Prospects and challenges

Aging causes progressive deterioration of daily rhythms in behavioral and metabolic processes and disruption in the regular sleep-wake cycle. Circadian disruption is directly related to diverse age-induced health abnormalities. Rising evidence from various organisms shows that core clock gene mutations cause premature aging, reduced lifespan, and sleeping irregularities. Improving the clock functions and correcting its disruption by pharmacological interventions or time-regulated feeding patterns could be a novel avenue for effective clinical management of aging and sleep disorders. To this end, many drugs for sleep disorders and anti-aging compounds interact with the core clock machinery and alter the circadian output. Evaluation of dosing time-dependency and circadian regulation of drug metabolism for therapeutic improvement of the existing drugs is another fundamental facet of chronomedicine. Multiple studies have demonstrated dose-dependent manipulation of the circadian period and phase-shifting by pharmacologically active compounds. The chronobiology research field is gradually moving towards the development of novel therapeutic strategies based on targeting the molecular clock or dosing time-oriented medications. However, such translational research ventures would require more experimental evidence from studies on humans. This review discusses the impact of circadian rhythms on aging and sleep, emphasizing the potentiality of circadian medicine in aging attenuation and sleep disorders.

Melatonin as a Chronobiotic with Sleep-promoting Properties

The use of exogenous melatonin (exo-MEL) as a sleep-promoting drug has been under extensive debate due to the lack of consistency of its described effects. In this study, we conduct a systematic and comprehensive review of the literature on the chronobiotic, sleep-inducing, and overall sleep-promoting properties of exo-MEL. To this aim, we first describe the possible pharmacological mechanisms involved in the sleep-promoting properties and then report the corresponding effects of exo-MEL administration on clinical outcomes in: a) healthy subjects, b) circadian rhythm sleep disorders, c) primary insomnia. Timing of administration and doses of exo-MEL received particular attention in this work. The exo-MEL pharmacological effects are hereby interpreted in view of changes in the physiological properties and rhythmicity of endogenous melatonin. Finally, we discuss some translational implications for the personalized use of exo-MEL in the clinical practice.

Melatonin as a Harmonizing Factor of Circadian Rhythms, Neuronal Cell Cycle and Neurogenesis: Additional Arguments for Its Therapeutic Use in Alzheimer's Disease

The synthesis and release of melatonin in the brain harmonize various physiological functions. The apparent decline in melatonin levels with advanced aging is an aperture to the neurodegenerative processes. It has been indicated that down regulation of melatonin leads to alterations of circadian rhythm components, which further causes a desynchronization of several genes and results in an increased susceptibility to develop neurodegenerative diseases. Additionally, as circadian rhythms and memory are intertwined, such rhythmic disturbances influence memory formation and recall. Besides, cell cycle events exhibit a remarkable oscillatory system, which is downstream of the circadian phenomena. The linkage between the molecular machinery of the cell cycle and complex fundamental regulatory proteins emphasizes the conjectural regulatory role of cell cycle components in neurodegenerative disorders such as Alzheimer's disease. Among the mechanisms intervening long before the signs of the disease appear, the disturbances of the circadian cycle, as well as the alteration of the machinery of the cell cycle and impaired neurogenesis, must hold our interest. Therefore, in the present review, we propose to discuss the underlying mechanisms of action of melatonin in regulating the circadian rhythm, cell cycle components and adult neurogenesis in the context of AD pathogenesis with the view that it might further assist to identify new therapeutic targets.

Novel Therapeutics for Treating Sleep Disorders: New Perspectives on Maydis stigma

Sleep is a restorative period that plays a crucial role in the physiological functioning of the body, including that of the immune system, memory processing, and cognition. Sleep disturbances can be caused by various physical, mental, and social problems. Recently, there has been growing interest in sleep. Maydis stigma (MS, corn silk) is a female maize flower that is traditionally used as a medicinal plant to treat many diseases, including hypertension, edema, and diabetes. It is also used as a functional food in tea and other supplements. β-Sitosterol (BS) is a phytosterol and a natural micronutrient in higher plants, and it has a similar structure to cholesterol. It is a major component of MS and has anti-inflammatory, antidepressive, and sedative effects. However, the potential effects of MS on sleep regulation remain unclear. Here, we investigated the effects of MS on sleep in mice. The effects of MS on sleep induction were determined using pentobarbital-induced sleep and caffeine-induced sleep disruption mouse models. MS extracts decreased sleep latency and increased sleep duration in both the pentobarbital-induced sleep induction and caffeine-induced sleep disruption models compared to the positive control, valerian root extract. The butanol fraction of MS extracts decreased sleep latency time and increased sleep duration. In addition, β-sitosterol enhances sleep latency and sleep duration. Both MS extract and β-sitosterol increased alpha activity in the EEG analysis. We measured the mRNA expression of melatonin receptors 1 and 2 (MT1/2) using qRT-PCR. The mRNA expression of melatonin receptors 1 and 2 was increased by MS extract and β-sitosterol treatment in rat primary cultured neurons and the brain. In addition, MS extract increased the expression of clock genes including per1/2, cry1/2, and Bmal1 in the brain. MS extract and β-sitosterol increased the phosphorylation of ERK1/2 and αCaMKII. Our results demonstrate for the first time that MS has a sleep-promoting effect via melatonin receptor expression, which may provide new scientific evidence for its use as a potential therapeutic agent for the treatment and prevention of sleep disturbance.

Sex-Dependent Effects of Piromelatine Treatment on Sleep-Wake Cycle and Sleep Structure of Prenatally Stressed Rats

Prenatal stress (PNS) impairs the circadian rhythm of the sleep/wake cycle. The melatonin (MT) analogue Piromelatine (Pir) was designed for the treatment of insomnia. The present study aimed to explore effects of Pir on circadian rhythmicity, motor activity, and sleep structure in male and female rats with a history of prenatal stress (PNS). In addition, we elucidated the role of MT receptors and brain-derived neurotrophic factor (BDNF) to ascertain the underlying mechanism of the drug. Pregnant rats were exposed to different stressors from day seven until birth. Piromelatine (20 mg/kg/day/14 days) was administered to young adult offspring. Home-cage locomotion, electroencephalographic (EEG) and electromyographic (EMG) recordings were conducted for 24 h. Offspring treated with vehicle showed sex-and phase-dependent disturbed circadian rhythm of motor activity and sleep/wake cycle accompanied by elevated rapid eye movement (REM) pattern and theta power and diminished non-rapid eye movement (NREM) sleep and delta power. While Pir corrected the PNS-induced impaired sleep patterns, the MT receptor antagonist luzindol suppressed its effects in male and female offspring. In addition, Pir increased the BDNF expression in the hippocampus in male and female offspring with PNS. Our findings suggest that the beneficial effect of Pir on PNS-induced impairment of sleep/wake cycle circadian rhythm and sleep structure is exerted via activation of MT receptors and enhanced BDNF expression in the hippocampus in male and female offspring.

The Role of Tryptophan Metabolites in Neuropsychiatric Disorders

In recent decades, neuropsychiatric disorders such as major depressive disorder, schizophrenia, bipolar, etc., have become a global health concern, causing various detrimental influences on patients. Tryptophan is an important amino acid that plays an indisputable role in several physiological processes, including neuronal function and immunity. Tryptophan’s metabolism process in the human body occurs using different pathways, including the kynurenine and serotonin pathways. Furthermore, other biologically active components, such as serotonin, melatonin, and niacin, are by-products of Tryptophan pathways. Current evidence suggests that a functional imbalance in the synthesis of Tryptophan metabolites causes the appearance of pathophysiologic mechanisms that leads to various neuropsychiatric diseases. This review summarizes the pharmacological influences of tryptophan and its metabolites on the development of neuropsychiatric disorders. In addition, tryptophan and its metabolites quantification following the neurotransmitters precursor are highlighted. Eventually, the efficiency of various biomarkers such as inflammatory, protein, electrophysiological, genetic, and proteomic biomarkers in the diagnosis/treatment of neuropsychiatric disorders was discussed to understand the biomarker application in the detection/treatment of various diseases.

Design and Validation of the First Family of Photo-Activatable Ligands for Melatonin Receptors

Melatonin is a neurohormone released in a circadian manner with peak levels at night. Melatonin mediates its effects mainly through G protein-coupled MT₁ and MT₂ receptors. Drugs acting on melatonin receptors are indicated for circadian rhythm- and sleep-related disorders. Tools to study the activation of these receptors with high temporal resolution are lacking. Here, we synthesized a family of light-activatable caged compounds by attaching o-nitrobenzyl (o-NB) or coumarin photocleavable groups to melatonin indolic nitrogen. All caged compounds showed the expected decrease in binding affinity for MT₁ and MT₂. The o-NB derivative MCS-0382 showed the best uncaging and biological properties, with 250-fold increase in affinity and potency upon illumination. Generation of melatonin from MCS-0382 was further demonstrated by its ability to modulate the excitation of SCN neurons in rat brain slices. MCS-0382 is available to study melatonin effects in a temporally controlled manner in cellular and physiological settings.

Night shift hormone: How does melatonin affect depression?

Melatonin is the main hormone secreted by the pineal gland that modulates the circadian rhythm and mood. Previous studies have shown the therapeutic effects of melatonin, or its important analogue, agomelatine, on depression. In this review study, we aimed to discuss the potential mechanisms of melatonin involved in the treatment of depression. It was noted that disrupted circadian rhythm can lead to depressive state, and melatonin via regulating circadian rhythm shows a therapeutic effect. It was also noted that melatonin induces antidepressant effects via promoting antioxidant system and neurogenesis, and suppressing oxidative stress, neuroinflammation, and apoptosis. The interaction effect between melatonin or agomelatine and serotonergic signaling has a significant effect on depression. It was noted that the psychotropic effects of agomelatine are induced by the synergistic interaction between melatonin and 5-HT_2C receptors. Agomelatine also interacts with glutamatergic signaling in brain regions involved in regulating mood and circadian rhythm. Interestingly, it was concluded that melatonin exerts both pro- and anti-inflammatory effects, depending on the grade of inflammation. It was suggested that synergistic interaction between melatonin and 5-HT_2C receptors may be able to induce therapeutic effects on other psychiatric disorders. Furthermore, dualistic role of melatonin in regulating inflammation is an important point that can be examined at different levels of inflammation in animal models of depression.

Shumian Capsule Improves the Sleep Disorder and Mental Symptoms Through Melatonin Receptors in Sleep-Deprived Mice

Healthy sleep is vital to maintaining the body's homeostasis. With the development of modern society, sleep disorder has gradually become one of the most epidemic health problems worldwide. Shumian capsule (SMC), a kind of traditional Chinese medicine (TCM) commonly used for insomnia, exhibits antidepressant and sedative effects in clinical practice. However, the underlying mechanisms have not been fully clarified. With the aid of a network pharmacology approach and function enrichment analysis, we identified the involvement of melatonin receptors in the antidepressant and sedative effects of SMC. In sleep-deprived mice, SMC treatment significantly alleviated insomnia and relevant mental alterations by improving both sleep latency and sleep duration. However, ramelteon, a selective melatonin receptor agonist that has been approved for the treatment of insomnia, only improved sleep latency. Additionally, SMC exhibited comparable effects on mental alterations with ramelteon as determined by an open-field test (OFT) and forced swimming test (FST). Mechanistically, we revealed that the melatonin receptor MT1 and MT2 signaling pathways involved the therapeutic effects of SMC. In addition to the single effect of traditional melatonin receptor agonists on treating sleep onset insomnia, SMC had therapeutic potential for various sleep disorders, such as sleep onset insomnia and sleep maintenance insomnia. Convergingly, our findings provide theoretical support for the clinical application of SMC.

Multiplexed Visualization Method to Explore Complete Targeting Regulatory Relationships Among Circadian Genes for Insomnia Treatment

Understanding the complete map of melatonin synthesis, the information transfer network among circadian genes in pineal gland, promises to resolve outstanding issues in endocrine systems and improve the clinical diagnosis and treatment level of insomnia, immune disease and hysterical depression. Currently, some landmark studies have revealed some genes that regulate circadian rhythm associated with melatonin synthesis. However, these studies don't give a complete map of melatonin synthesis, as transfer information among circadian genes in pineal gland is lost. New biotechnology, integrates dynamic sequential omics and multiplexed imaging method, has been used to visualize the complete process of melatonin synthesis. It is found that there are two extremely significant information transfer processes involved in melatonin synthesis. In the first stage, as the light intensity decreased, melatonin synthesis mechanism has started, which is embodied in circadian genes, Rel, Polr2A, Mafk, and Srbf1 become active. In the second stage, circadian genes Hif1a, Bach1, Clock, E2f6, and Per2 are regulated simultaneously by four genes, Rel, Polr2A, Mafk, and Srbf1 and contribute genetic information to Aanat. The expeditious growth in this technique offer reference for an overall understanding of gene-to-gene regulatory relationship among circadian genes in pineal gland. In the study, dynamic sequential omics and the analysis process well provide the current state and future perspectives to better diagnose and cure diseases associated with melatonin synthesis disorder.

Radiosynthesis and In Vivo Evaluation of Four Positron Emission Tomography Tracer Candidates for Imaging of Melatonin Receptors

Melatonin is a neurohormone that modulates several physiological functions in mammals through the activation of melatonin receptor type 1 and 2 (MT₁ and MT₂). The melatonergic system is an emerging therapeutic target for new pharmacological interventions in the treatment of sleep and mood disorders; thus, imaging tools to further investigate its role in the brain are highly sought-after. We aimed to develop selective radiotracers for in vivo imaging of both MT₁ and MT₂ by positron emission tomography (PET). We identified four previously reported MT ligands with picomolar affinities to the target based on different scaffolds which were also amenable for radiolabeling with either carbon-11 or fluorine-18. [¹¹C]UCM765, [¹¹C]UCM1014, [¹⁸F]3-fluoroagomelatine ([¹⁸F]3FAGM), and [¹⁸F]fluoroacetamidoagomelatine ([¹⁸F]FAAGM) have been synthesized in high radiochemical purity and evaluated in wild-type rats. All four tracers showed moderate to high brain permeability in rats with maximum standardized uptake values (SUV_max of 2.53, 1.75, 3.25, and 4.47, respectively) achieved 1-2 min after tracer administration, followed by a rapid washout from the brain. Several melatonin ligands failed to block the binding of any of the PET tracer candidates, while in some cases, homologous blocking surprisingly resulted in increased brain retention. Two ¹⁸F-labeled agomelatine derivatives were brought forward to PET scans in non-human primates and autoradiography on human brain tissues. No specific binding has been detected in blocking studies. To further investigate pharmacokinetic properties of the putative tracers, microsomal stability, plasma protein binding, log D, and membrane bidirectional permeability assays have been conducted. Based on the results, we conclude that the fast first pass metabolism by the enzymes in liver microsomes is the likely reason of the failure of our PET tracer candidates. Nevertheless, we showed that PET imaging can serve as a valuable tool to investigate the brain permeability of new therapeutic compounds targeting the melatonergic system.

Sleep Quality: A Narrative Review on Nutrition, Stimulants, and Physical Activity as Important Factors

Sleep is a cyclically occurring, transient, and functional state that is controlled primarily by neurobiological processes. Sleep disorders and insomnia are increasingly being diagnosed at all ages. These are risk factors for depression, mental disorders, coronary heart disease, metabolic syndrome, and/or high blood pressure. A number of factors can negatively affect sleep quality, including the use of stimulants, stress, anxiety, and the use of electronic devices before sleep. A growing body of evidence suggests that nutrition, physical activity, and sleep hygiene can significantly affect the quality of sleep. The aim of this review was to discuss the factors that can affect sleep quality, such as nutrition, stimulants, and physical activity.

The rationale for treating uveal melanoma with adjuvant melatonin: a review of the literature

Background

Uveal melanoma is a rare form of cancer with high mortality. The incidence of metastases is attributed to early seeding of micrometastases from the eye to distant organs, primarily the liver. Once these seeded clusters of dormant tumor cells grow into larger radiologically detectable macrometastases, median patient survival is about 1 year. Melatonin is an important hormone for synchronizing circadian rhythms. It is also involved in other aspects of human physiology and may offer therapeutic benefits for a variety of diseases including cancer.

Methods

Articles involving the physiological effects of melatonin, pharmacokinetics, and previous use in cancer studies were acquired using a comprehensive literature search in the Medline (PubMed) and Web of Science databases. In total, 147 publications were selected and included in the review.

Results

Melatonin has been observed to suppress the growth of cancer cells, inhibit metastatic spread, enhance immune system functions, and act as an anti-inflammatory in both in vitro and in vivo models. Melatonin may also enhance the efficacy of cancer treatments such as immuno- and chemotherapy. Numerous studies have shown promising results for oral melatonin supplementation in patients with other forms of cancer including cutaneous malignant melanoma. Cell line and animal studies support a hypothesis in which similar benefits may exist for uveal melanoma.

Conclusions

Given its low cost, good safety profile, and limited side effects, there may be potential for the use of melatonin as an adjuvant oncostatic treatment. Future avenues of research could include clinical trials to evaluate the effect of melatonin in prevention of macrometastases of uveal melanoma.

Melatonin as an antioxidant agent in disease prevention: A biochemical focus

Abstract:

In the recent years, free radicals and oxidative stress have been found to be associated with aging, cancer, atherosclerosis, neurodegenerative disorders, diabetes, and inflammatory diseases. Confirming the role of oxidants in numerous pathological situations including cancer, developing antioxidants as therapeutic platforms is needed. It has been well established that melatonin and its derived metabolites function as endogenous free-radical scavengers and broad spectrum antioxidants. To achieve this function, melatonin can directly detoxify reactive oxygen and reactive nitrogen species and indirectly overexpress antioxidant enzymes while suppressing the activity of pro-oxidant enzymes. Many investigations have also confirmed the role of melatonin and its derivatives in different physiological processes and therapeutic functions such as controlling the circadian rhythm and immune functions. This review aimed to focus on melatonin as a beneficial agent for the stimulation of antioxidant enzymes and inhibition of lipid peroxidation and to evaluate its contribution to protection against oxidative damages. In addition, the clinical application of melatonin in several diseases is discussed. Finally, the safety and efficacy of melatonin in clinical backgrounds is also reviewed.

Structural basis of the ligand binding and signaling mechanism of melatonin receptors

Melatonin receptors (MT₁ and MT₂ in humans) are family A G protein-coupled receptors that respond to the neurohormone melatonin to regulate circadian rhythm and sleep. Numerous efforts have been made to develop drugs targeting melatonin receptors for the treatment of insomnia, circadian rhythm disorder, and cancer. However, designing subtype-selective melatonergic drugs remains challenging. Here, we report the cryo-EM structures of the MT₁-G_i signaling complex with 2-iodomelatonin and ramelteon and the MT₂-G_i signaling complex with ramelteon. These structures, together with the reported functional data, reveal that although MT₁ and MT₂ possess highly similar orthosteric ligand-binding pockets, they also display distinctive features that could be targeted to design subtype-selective drugs. The unique structural motifs in MT₁ and MT₂ mediate structural rearrangements with a particularly wide opening on the cytoplasmic side. G_i is engaged in the receptor core shared by MT₁ and MT₂ and presents a conformation deviating from those in other G_i complexes. Together, our results provide new clues for designing melatonergic drugs and further insights into understanding the G protein coupling mechanism.

New uses of Melatonin as a Drug, a Review

Melatonin is a simple compound with a proper chemical name N-acetyl-5-methoxy tryptamine and known as a hormone controlling circadian rhythm. Humans produce melatonin at night which is the reason for sleeping in the night and awakening over the day. Melatonin interacts with melatonin receptors MT1 and MT2 but it was also revealed that melatonin is a strong antioxidant and it also has a role in regulation of cell cycle. Currently, melatonin is used as a drug for some types of sleep disorder but the recent research points to the fact that melatonin can also serve for the other purposes including prophylaxis or therapy of lifestyle diseases, cancer, neurodegenerative disorders and exposure to chemicals. This review summarizes basic facts and direction of the current research on melatonin. The actual literature was scrutinized for the purpose of this review.