Melatonin promotes sleep in mice by inhibiting orexin neurons in the perifornical lateral hypothalamus

Dopamine D2 receptors in the accumbal core region mediates the effects of fentanyl on sleep-wakefulness

Fentanyl, a potent analgesic and addictive substance, significantly impacts sleep-wakefulness (S-W). Acutely, it promotes wake, whereas chronic abuse leads to severe sleep disruptions, including insomnia, which contributes to opioid use disorders (OUD), a chronic brain disease characterized by compulsive opioid use and harmful consequences. Although the critical association between sleep disruptions and fentanyl addiction is acknowledged, the precise mechanisms through which fentanyl influences sleep remain elusive. Recent studies highlight the role of the dopaminergic system of the nucleus accumbens (NAc) in S-W regulation, but its specific involvement in mediating fentanyl's effects on S-W remains unexplored. We hypothesized that dopamine D2 receptors mediate fentanyl-induced effects on S-W. To test this hypothesis, male C57BL/6J mice, instrumented with sleep recording electrodes and bilateral guide cannulas above the accumbal core region (NAcC), were utilized in this study. At dark onset, animals were bilaterally administered sulpiride (D2 receptors antagonist; 250 ng/side) in the NAcC followed by an intraperitoneal injection of fentanyl (1.2 mg/Kg). S-W was examined for the next 12 h. We found that systemic administration of fentanyl significantly increased wakefulness during the first 6 h of the dark which was followed by a significant increase in NREM and REM sleep during the second 6 h of the dark period. D2-receptor blockade significantly reduced this effect as evidenced by a significant reduction in fentanyl-induced wakefulness during first 6 h of dark period and sleep rebound during the second 6 h. Our findings suggest that D2 receptors in the NAcC plays a vital role in mediating the fentanyl-induced changes in S-W.

Melatonin's role in the timing of sleep onset is conserved in nocturnal mice

Melatonin supplementation strengthens non-restorative sleep rhythms and its temporal alignment in both humans and night-active rodents. Of note, although the sleep cycle is reversed in day-active and night-active (nocturnal) mammals, both, produce melatonin at night under the control of the circadian clock. The effects of exogenous melatonin on sleep and sleepiness are relatively clear, but its endogenous role in sleep, particularly, in timing sleep onset (SO), remains poorly understood. We show in nocturnal mice that the increases in mid-nighttime sleep episodes, and the mid-nighttime decline in activity, are coupled to nighttime melatonin signaling. Furthermore, we show that endogenous melatonin modulates SO by reducing the threshold for wake-to-sleep transitioning. Such link between melatonin and SO timing may explain phenomena such as increased sleep propensity in circadian rhythm sleep disorders and chronic insomnia in patients with severely reduced nocturnal melatonin levels. Our findings demonstrate that melatonin's role in sleep is evolutionarily conserved, effectively challenging the argument that melatonin cannot play a major role in sleep regulation in nocturnal mammals, where the main activity phase coincides with high melatonin levels.

Modulation of autophagy by melatonin and its receptors: implications in brain disorders

Autophagy plays a crucial role in maintaining neuronal homeostasis and function, and its disruption is linked to various brain diseases. Melatonin, an endogenous hormone that primarily acts through MT1 and MT2 receptors, regulates autophagy via multiple pathways. Growing evidence indicates that melatonin's ability to modulate autophagy provides therapeutic and preventive benefits in brain disorders, including neurodegenerative and affective diseases. In this review, we summarize the key mechanisms by which melatonin affects autophagy and explore its therapeutic potential in the treatment of brain disorders.

Melatonin, Melatonin Receptors and Sleep: Moving Beyond Traditional Views

Sleep, constituting approximately one-third of the human lifespan, is a crucial physiological process essential for physical and mental well-being. Normal sleep consists of an orderly progression through wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep, all of which are tightly regulated. Melatonin, often referred to as the "hormone of sleep," plays a pivotal role as a regulator of the sleep/wake cycle and exerts its effects through high-affinity G-protein coupled receptors known as MT1 and MT2. Selective modulation of these receptors presents a promising therapeutic avenue for sleep disorders. This review examines research on the multifaceted role of melatonin in sleep regulation, focusing on selective ligands targeting MT1 and MT2 receptors, as well as studies involving MT1 and MT2 knockout mice. Contrary to common beliefs, growing evidence suggests that melatonin, through MT1 and MT2 receptors, might not only influence circadian aspects of sleep but likely, also modulate the homeostatic process of sleep and sleep architecture, or could be the molecule linking the homeostatic and circadian regulation of sleep. Furthermore, the distinct brain localization of MT1 and MT2 receptors, with MT1 receptors primarily regulating REM sleep and MT2 receptors regulating NREM sleep, is discussed. Collectively, sleep regulation extends beyond the circulating levels and circadian peak of melatonin; it also critically involves the expression, molecular activation, and regulatory functions of MT1 and MT2 receptors across various brain regions and nuclei involved in the regulation of sleep. This research underscores the importance of ongoing investigation into the selective roles of MT1 and MT2 receptors in sleep. Such research efforts are expected to pave the way for the development of targeted MT1 or MT2 receptors ligands, thereby optimizing therapeutic interventions for sleep disorders.

Mechanisms underlying delirium in patients with critical illness

Delirium is an acute, global cognitive disorder syndrome, also known as acute brain syndrome, characterized by disturbance of attention and awareness and fluctuation of symptoms. Its incidence is high among critically ill patients. Once patients develop delirium, it increases the risk of unplanned extubation, prolongs hospital stay, increases the risk of nosocomial infection, post-intensive care syndrome-cognitive impairment, and even death. Therefore, it is of great importance to understand how delirium occurs and to reduce the incidence of delirium in critically ill patients. This paper reviews the potential pathophysiological mechanisms of delirium in critically ill patients, with the aim of better understanding its pathophysiological processes, guiding the formulation of effective prevention and treatment strategies, providing a basis for clinical medication.

Melatonin targets the paraventricular thalamus to promote non-rapid eye movement sleep in C3H/HeJ mice

Melatonin (MLT) is an important circadian signal for sleep regulation, but the neural circuitries underlying the sleep-promoting effects of MLT are poorly understood. The paraventricular thalamus (PVT) is a critical thalamic area for wakefulness control and expresses MLT receptors, raising a possibility that PVT neurons may mediate the sleep-promoting effects of MLT. Here, we found that MLT receptors were densely expressed on PVT neurons and exhibited circadian-dependent variations in C3H/HeJ mice. Application of exogenous MLT decreased the excitability of PVT neurons, resulting in hyperpolarization of membrane potential and reduction of action potential firing. MLT also inhibited the spontaneous activity of PVT neurons at both population and single-neuron levels in freely behaving mice. Furthermore, pharmacological manipulations revealed that local infusion of exogeneous MLT into the PVT promoted non-rapid eye movement (NREM) sleep and increased NREM sleep duration, whereas MLT receptor antagonists decreased NREM sleep. Moreover, we found that selectively knocking down endogenous MLT receptors in the PVT decreased NREM sleep and correspondingly increased wakefulness, with particular changes shortly after the onset of the dark or light phase. Taken together, these results demonstrate that PVT is an important target of MLT for promoting NREM sleep.

Melatonin: A potential nighttime guardian against Alzheimer's

In the context of the escalating global health challenge posed by Alzheimer's disease (AD), this comprehensive review considers the potential of melatonin in both preventive and therapeutic capacities. As a naturally occurring hormone and robust antioxidant, accumulating evidence suggests melatonin is a compelling candidate to consider in the context of AD-related pathologies. The review considers several mechanisms, including potential effects on amyloid-beta and pathologic tau burden, antioxidant defense, immune modulation, and regulation of circadian rhythms. Despite its promise, several gaps need to be addressed prior to clinical translation. These include conducting additional randomized clinical trials in patients with or at risk for AD dementia, determining optimal dosage and timing, and further determining potential side effects, particularly of long-term use. This review consolidates existing knowledge, identifies gaps, and suggests directions for future research to better understand the potential of melatonin for neuroprotection and disease mitigation within the landscape of AD.

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.

Melatonin improves synapse development by PI3K/Akt signaling in a mouse model of autism spectrum disorder

JOURNAL/nrgr/04.03/01300535-202407000-00043/figure1/v/2023-11-20T171125Z/r/image-tiff

Autism spectrum disorders are a group of neurodevelopmental disorders involving more than 1100 genes, including Ctnnd2 as a candidate gene. Ctnnd2 knockout mice, serving as an animal model of autism, have been demonstrated to exhibit decreased density of dendritic spines. The role of melatonin, as a neurohormone capable of effectively alleviating social interaction deficits and regulating the development of dendritic spines, in Ctnnd2 deletion-induced nerve injury remains unclear. In the present study, we discovered that the deletion of exon 2 of the Ctnnd2 gene was linked to social interaction deficits, spine loss, impaired inhibitory neurons, and suppressed phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signal pathway in the prefrontal cortex. Our findings demonstrated that the long-term oral administration of melatonin for 28 days effectively alleviated the aforementioned abnormalities in Ctnnd2 gene-knockout mice. Furthermore, the administration of melatonin in the prefrontal cortex was found to improve synaptic function and activate the PI3K/Akt signal pathway in this region. The pharmacological blockade of the PI3K/Akt signal pathway with a PI3K/Akt inhibitor, wortmannin, and melatonin receptor antagonists, luzindole and 4-phenyl-2-propionamidotetralin, prevented the melatonin-induced enhancement of GABAergic synaptic function. These findings suggest that melatonin treatment can ameliorate GABAergic synaptic function by activating the PI3K/Akt signal pathway, which may contribute to the improvement of dendritic spine abnormalities in autism spectrum disorders.

Digital automation of transdermal drug delivery with high spatiotemporal resolution

Transdermal drug delivery is of vital importance for medical treatments. However, user adherence to long-term repetitive drug delivery poses a grand challenge. Furthermore, the dynamic and unpredictable disease progression demands a pharmaceutical treatment that can be actively controlled in real-time to ensure medical precision and personalization. Here, we report a spatiotemporal on-demand patch (SOP) that integrates drug-loaded microneedles with biocompatible metallic membranes to enable electrically triggered active control of drug release. Precise control of drug release to targeted locations (<1 mm2), rapid drug release response to electrical triggers (<30 s), and multi-modal operation involving both drug release and electrical stimulation highlight the novelty. Solution-based fabrication ensures high customizability and scalability to tailor the SOP for various pharmaceutical needs. The wireless-powered and digital-controlled SOP demonstrates great promise in achieving full automation of drug delivery, improving user adherence while ensuring medical precision. Based on these characteristics, we utilized SOPs in sleep studies. We revealed that programmed release of exogenous melatonin from SOPs improve sleep of mice, indicating potential values for basic research and clinical treatments.

iMS-Bmal1-/- mice show evident signs of sarcopenia that are counteracted by exercise and melatonin therapies

Sarcopenia is an age-related disease characterized by a reduction in muscle mass, strength, and function and, therefore, a deterioration in skeletal muscle health and frailty. Although the cause of sarcopenia is still unknown and, thus, there is no treatment, increasing evidence suggests that chronodisruption, particularly alterations in Bmal1 clock gene, can lead to those deficits culminating in sarcopenia. To gain insight into the cause and mechanism of sarcopenia and the protective effect of a therapeutic intervention with exercise and/or melatonin, the gastrocnemius muscles of male and female skeletal muscle-specific and inducible Bmal1 knockout mice (iMS-Bmal1-/- ) were examined by phenotypic tests and light and electron microscopy. Our results revealed a disruption of the normal activity/rest rhythm, a drop in skeletal muscle function and mass, and increased frailty in male and female iMS-Bmal1-/- animals compared to controls. A reduction in muscle fiber size and increased collagenous tissue were also detected, accompanied by reduced mitochondrial oxidative capacity and a compensatory shift towards a more oxidative fiber type. Electron microscopy further supports mitochondrial impairment in mutant mice. Melatonin and exercise ameliorated the damage caused by loss of Bmal1 in mutant mice, except for mitochondrial damage, which was worsened by the latter. Thus, iMS-Bmal1-/- mice let us to identify Bmal1 deficiency as the responsible for the appearance of sarcopenia in the gastrocnemius muscle. Moreover, the results support the exercise and melatonin as therapeutic tools to counteract sarcopenia, by a mechanism that does not require the presence of Bmal1.

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.

Current Considerations in the Diagnosis and Treatment of Circadian Rhythm Sleep-Wake Disorders in Children

Circadian Rhythm Sleep-Wake Disorders (CRSWDs) are important sleep disorders whose unifying feature is a mismatch between the preferred or required times for sleep and wakefulness and the endogenous circadian drives for these. Their etiology, presentation, and treatment can be different in pediatric patients as compared to adults. Evaluation of these disorders must be performed while viewed through the lens of a patient's comorbid conditions. Newer methods of assessment promise to provide greater diagnostic clarity and critical insights into how circadian physiology affects overall health and disease states. Effective clinical management of CRSWDs is multimodal, requiring an integrated approach across disciplines. Therapeutic success depends upon appropriately timed nonpharmacologic and pharmacologic interventions. A better understanding of the genetic predispositions for and causes of CRSWDs has led to novel clinical opportunities for diagnosis and improved therapeutics.

Sleep dysfunction mediates the relationship between hypothalamic-insula connectivity and anxiety-depression symptom severity bidirectionally in young adults

BACKGROUND

The hypothalamus plays a crucial role in regulating sleep-wake cycle and motivated behavior. Sleep disturbance is associated with impairment in cognitive and affective functions. However, how hypothalamic dysfunction may contribute to inter-related sleep, cognitive, and emotional deficits remain unclear.

METHODS

We curated the Human Connectome Project dataset and investigated how hypothalamic resting state functional connectivities (rsFC) were associated with sleep dysfunction, as evaluated by the Pittsburgh Sleep Quality Index (PSQI), cognitive performance, and subjective mood states in 687 young adults (342 women). Imaging data were processed with published routines and evaluated with a corrected threshold. We examined the inter-relationship amongst hypothalamic rsFC, PSQI score, and clinical measures with mediation analyses.

RESULTS

In whole-brain regressions with age and drinking severity as covariates, men showed higher hypothalamic rsFC with the right insula in correlation with PSQI score. No clusters were identified in women at the same threshold. Both hypothalamic-insula rsFC and PSQI score were significantly correlated with anxiety and depression scores in men. Further, mediation analyses showed that PSQI score mediated the relationship between hypothalamic-insula rsFC and anxiety/depression symptom severity bidirectionally in men.

CONCLUSIONS

Sleep dysfunction is associated with negative emotions and hypothalamic rsFC with the right insula, a core structure of the interoceptive circuits. Notably, anxiety-depression symptom severity and altered hypothalamic-insula rsFC are related bidirectionally by poor sleep quality. These findings are specific to men, suggesting potential sex differences in the neural circuits regulating sleep and emotional states that need to be further investigated.

Melatonin protects human nucleus pulposus cells from pyroptosis by regulating Nrf2 via melatonin membrane receptors

Aims

This study was performed to explore the effect of melatonin on pyroptosis in nucleus pulposus cells (NPCs) and the underlying mechanism of that effect.

Methods

This experiment included three patients diagnosed with lumbar disc herniation who failed conservative treatment. Nucleus pulposus tissue was isolated from these patients when they underwent surgical intervention, and primary NPCs were isolated and cultured. Western blotting, reverse transcription polymerase chain reaction, fluorescence staining, and other methods were used to detect changes in related signalling pathways and the ability of cells to resist pyroptosis.

Results

Western blot analysis confirmed the expression of cleaved CASP-1 and melatonin receptor (MT-1A-R) in NPCs. The cultured NPCs were identified by detecting the expression of CD24, collagen type II, and aggrecan. After treatment with hydrogen peroxide, the pyroptosis-related proteins NLR family pyrin domain containing 3 (NLRP3), cleaved CASP-1, N-terminal fragment of gasdermin D (GSDMD-N), interleukin (IL)-18, and IL-1β in NPCs were upregulated, and the number of propidium iodide (PI)-positive cells was also increased, which was able to be alleviated by pretreatment with melatonin. The protective effect of melatonin on pyroptosis was blunted by both the melatonin receptor antagonist luzindole and the nuclear factor erythroid 2–related factor 2 (Nrf2) inhibitor ML385. In addition, the expression of the transcription factor Nrf2 was up- or downregulated when the melatonin receptor was activated or blocked by melatonin or luzindole, respectively.

Conclusion

Melatonin protects NPCs against reactive oxygen species-induced pyroptosis by upregulating the transcription factor Nrf2 via melatonin receptors.

Cite this article: Bone Joint Res 2023;12(3):202–211.

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.

Selective activation of the hypothalamic orexinergic but not melanin-concentrating hormone neurons following pilocarpine-induced seizures in rats

Introduction

Sleep disorders are common comorbidities in patients with temporal lobe epilepsy (TLE), but the underlying mechanisms remain poorly understood. Since the lateral hypothalamic (LH) and the perifornical orexinergic (ORX) and melanin-concentrating hormone (MCH) neurons are known to play opposing roles in the regulation of sleep and arousal, dysregulation of ORX and MCH neurons might contribute to the disturbance of sleep-wakefulness following epileptic seizures.

Methods

To test this hypothesis, rats were treated with lithium chloride and pilocarpine to induce status epilepticus (SE). Electroencephalogram (EEG) and electromyograph (EMG) were recorded for analysis of sleep-wake states before and 24 h after SE. Double-labeling immunohistochemistry of c-Fos and ORX or MCH was performed on brain sections from the epileptic and control rats. In addition, anterograde and retrograde tracers in combination with c-Fos immunohistochemistry were used to analyze the possible activation of the amygdala to ORX neural pathways following seizures.

Results

It was found that epileptic rats displayed prolonged wake phase and decreased non-rapid eye movement (NREM) and rapid eye movement (REM) phase compared to the control rats. Prominent neuronal activation was observed in the amygdala and the hypothalamus following seizures. Interestingly, in the LH and the perifornical nucleus, ORX but not MCH neurons were significantly activated (c-Fos+). Neural tracing showed that seizure-activated (c-Fos+) ORX neurons were closely contacted by axon terminals originating from neurons in the medial amygdala.

Discussion

These findings suggest that the spread of epileptic activity from amygdala to the hypothalamus causes selective activation of the wake-promoting ORX neurons but not sleep-promoting MCH neurons, which might contribute to the disturbance of sleep-wakefulness in TLE.

Ischemic Stroke Disrupts Sleep Homeostasis in Middle-Aged Mice

Sleep disturbances, including insomnia and excessive daytime sleepiness, are highly prevalent in patients with ischemic stroke (IS), which severely impacts recovery and rehabilitation efforts. However, how IS induces sleep disturbances is unclear. Three experiments were performed on middle-aged C57BL/6J mice, instrumented with sleep recording electrodes and/or subjected to 1 h of middle cerebral artery (MCAO; Stroke group) or sham (Sham group) occlusion to induce IS. After 48 h of reperfusion (a) experiment 1 verified sensorimotor deficit (using Garcia scale) and infarction (using TTC staining) in this mouse model; (b) experiment 2 examined the effects of IS on the quality (sleep latency and NREM delta power) and quantity (duration) of sleep; and (c) experiment 3 determined the effects of IS on sleep homeostasis using sleep deprivation (SD) and recovery sleep (RS) paradigm. Stroke mice display (a) a significant correlation between sensorimotor deficit and cerebral infarction; (b) insomnia-like symptoms (increased sleep latency, reduced NREM duration and delta power) during the light (inactive) period and daytime sleepiness-like symptoms during the dark (active) period mimicking sleep in IS patients; and (c) impairments in the markers of sleep pressure (during SD) and sleep dissipation (during RS). Our results suggest that IS disrupts sleep homeostasis to cause sleep disturbances.

Effects of melatonin on intestinal function and bacterial compositions in sucking piglets

Melatonin has been reported to affect intestinal function by targeting microbiome, morphological structure, barrier integrity and nutrient absorptive system. While the effect of melatonin on intestinal development in newborn infants is obscure, thus, this study firstly attempted to investigate the hypothesis that melatonin treatment improves intestinal development in sucking piglets. 14 healthy newborn piglets received 10 ml melatonin solution (1 mg/ml) or drinking water (n = 7) for 21 days. The results showed that oral administration of melatonin increased liver relative weight (p < 0.05) but failed to affect growth performance in sucking piglets (p > 0.05). Immunostaining jejunal samples from melatonin group showed high expressions of nnos and claudin1, indicating that melatonin improved intestinal neural development and barrier integrity. Also, melatonin promoted intestinal absorptive function evidenced by the increased serum proline concentration in melatonin-treated piglets compared with the control (p < 0.05). Gut microbiota compositions were tested by 16S rDNA sequencing and the results showed that melatonin increased the relative abundance of Actinobacteria compared with the control (p < 0.05) at the phylum level. However, Selenomonadales was markedly reduced compared with the control at the order level (p < 0.05). Gut and faecal volatile fatty acids were tested to evaluate the microbiota metabolism, but no difference was noticed in volatile fatty acid concentrations (p > 0.05). Melatonin improved intestinal development by affecting neural development, barrier integrity, nutrient absorption and microbiota in sucking piglets.

Neuromodulatory and Protective Effects Induced by the Association of Herbal Extracts from Valeriana officinalis, Ziziphus jujuba, and Humulus lupulus with Melatonin: An Innovative Formulation for Counteracting Sleep Disorders

Background: The use of herbal extracts could represent an advantageous approach for treating sleeping disorders, especially in mild-to-moderate conditions, before the onset of a specific therapy with first-line drugs. Specifically, the focus was posed about the use of extracts from Valeriana officinalis, Ziziphus jujuba, and Humulus lupulus. Multiple studies demonstrated the efficacy of these medicinal plants to positively manage insomnia symptoms. Additionally, their efficacy in the treatment of sleeping disorders could also be improved by their pharmacological association. In the present study, extracts from Valeriana officinalis, Ziziphus jujuba, Humulus lupulus, melatonin, and their pharmacological association, Vagonotte® MEL, were studied for potential application in the treatment of insomnia. Methods: The extracts and melatonin were tested on hypothalamic neurons and tissue for evaluating biocompatibility and protective and neuromodulatory effects. The neuromodulatory effects were evaluated as orexin A gene expression and serotonin steady state level, in the hypothalamus. Results: The extracts and melatonin, although with evident differences, were effective as antioxidant and anti-inflammatory agents; additionally, they were also able to reduce the hypothalamic gene expression of orexin A and the steady state level of serotonin, playing master roles in wakefulness. It is noteworthy that the formulation displayed all the effects of the single ingredients, without any sign of toxicity and pharmacological interference in the hypothalamus. Conclusions: Concluding, the present study explored the biological effects of melatonin and herbal extracts with phytotherapy interest in V. officinalis, Z. jujuba, and H. lupulus. The study demonstrated their intrinsic scavenging/reducing activity, together with protective and neuromodulatory effects in the hypothalamus, with a significant reduction of both orexin A gene expression and serotonin steady state level. Additionally, the study also considered their pharmacological association, which displayed an overall pharmacological spectrum mirroring, including all the effects of the single ingredients, without showing any sign of toxicity in the brain and interference between the extracts and melatonin.

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.

Melatonin inhibits Gram-negative pathogens by targeting citrate synthase

Bacterial infections caused by Gram-negative pathogens represent a growing burden for public health worldwide. Despite the urgent need for new antibiotics that effectively fight against pathogenic bacteria, very few compounds are currently under development or approved in the clinical setting. Repurposing compounds for other uses offers a productive strategy for the development of new antibiotics. Here we report that the multifaceted melatonin effectively improves survival rates of mice and decreases bacterial loads in the lung during infection. Mechanistically, melatonin specifically inhibits the activity of citrate synthase of Gram-negative pathogens through directly binding to the R300, D363, and H265 sites, particularly for the notorious Pasteurella multocida. These findings highlight that usage of melatonin is a feasible and alternative therapy to tackle the increasing threat of Gram-negative pathogen infections via disrupting metabolic flux of bacteria.

Mechanisms of Melatonin in Obesity: A Review

Obesity and its complications have become a prominent global public health problem that severely threatens human health. Melatonin, originally known as an effective antioxidant, is an endogenous hormone found throughout the body that serves various physiological functions. In recent decades, increasing attention has been paid to its unique function in regulating energy metabolism, especially in glucose and lipid metabolism. Accumulating evidence has established the relationship between melatonin and obesity; nevertheless, not all preclinical and clinical evidence indicates the anti-obesity effect of melatonin, which makes it remain to conclude the clinical effect of melatonin in the fight against obesity. In this review, we have summarized the current knowledge of melatonin in regulating obesity-related symptoms, with emphasis on its underlying mechanisms. The role of melatonin in regulating the lipid profile, adipose tissue, oxidative stress, and inflammation, as well as the interactions of melatonin with the circadian rhythm, gut microbiota, sleep disorder, as well as the α7nAChR, the opioidergic system, and exosomes, make melatonin a promising agent to open new avenues in the intervention of obesity.

Combination of Melatonin and Zoledronic Acid Suppressed the Giant Cell Tumor of Bone in vitro and in vivo

Melatonin (Mlt) confers potential antitumor effects in various types of cancer. However, to the best of our knowledge, the role of Mlt in the giant cell tumor of bone (GCTB) remains unknown. Moreover, further research is required to assess whether Mlt can enhance the therapeutic effect of zoledronic acid (Zol), a commonly used anti-GCTB drug. In this research, we investigated the effects of Mlt, Zol, and the combination of these two drugs on GCTB cells’ characteristics, including cell proliferation, apoptosis, osteogenic differentiation, migration, and invasion. The cell counting kit-8 (CCK-8) assay, colony formation assay, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay (TUNEL), alkaline phosphatase (ALP) staining, alizarin red staining (ARS), scratch wound healing assay, and transwell experiment were performed, respectively. Our results showed that Mlt could effectively inhibit the proliferation, migration, and invasion of GCTB cells, as well as promote the apoptosis and osteogenic differentiation of tumor cells. Of note, a stronger antitumor effect was observed when Mlt was combined with Zol treatment. This therapeutic effect might be achieved by inhibiting the activation of both the Hippo and NF-κB pathways. In conclusion, our study suggests that Mlt can be a new treatment for GCTB, which could further enhance the antitumor effect of Zol.

Perioperative Sleep Disorder: A Review

Patients in the perioperative period usually present with different types and degrees of sleep disorders, which can severely affect their post-operative outcomes. Multiple risk factors may lead to the occurrence of perioperative sleep disorders, including personal factors, psychological factors, surgery factors, and environmental factors. In this review, we summarize the potential risk factors for perioperative sleep disorders during hospitalization. And it also provides an overview of perioperative outcomes and potential therapeutic prevention of perioperative sleep disorders. However, the further search is necessary to investigate the effectiveness and safety of preventions in the clinical practice and push forward the therapies.

Gene duplication and loss of AANAT in mammals driven by rhythmic adaptations

Arylalkylamine N-acetyltransferase (AANAT) plays a crucial role in synchronizing internal biological functions to circadian and circannual changes. Generally speaking, only one copy of AANAT gene has been found in mammals, however, three independent duplications of this gene were detected in several cetartiodactyl lineages (i.e., Suidae, Hippopotamidae, and Pecora), which originated in the middle Eocene, a geological period characterized with the increased climate seasonality. Lineage-specific expansions of AANAT and the associated functional enhancement in these lineages strongly suggest an improvement in regulating photoperiodic response to adapt to seasonal climate changes. In contrast, independent inactivating mutations or deletions of the AANAT locus were identified in the four pineal-deficient clades (cetaceans, sirenians, xenarthrans, and pangolins). Loss of AANAT function in cetaceans and sirenians could disrupt the sleep-promoting effects of pineal melatonin, which might contribute to increasing wakefulness, adapting these clades to underwater sleep. The absence of AANAT and pineal glands in xenarthrans and pangolins may be associated with their body temperature maintenance. The present work demonstrates a far more complex and intriguing evolutionary pattern and functional diversity of mammalian AANAT genes than previously thought and provides further evidence for understanding AANAT evolution as driven by rhythmic adaptations in mammals.

Melatonin ameliorates the sleep disorder induced by surgery under sevoflurane anaesthesia in aged mice

Post-operative sleep disorders induce adverse effects on patients, especially the elderly, which may be associated with surgery and inhalational anaesthetics. Melatonin is a neuroendocrine regulator of the sleep-wake cycle. In this study, we analysed the alterations of post-operative sleep in aged melatonin-deficient (C57BL/6J) mice, and investigated if exogenous melatonin could facilitate entrainment of circadian rhythm after laparotomy under sevoflurane anaesthesia. The results showed that laparotomy under sevoflurane anaesthesia had a greater influence on post-operative sleep than sevoflurane alone. Laparotomy under anaesthesia led to circadian rhythm shifting forward, altered EEG power density and delta power of NREM sleep, and lengthened REM and NREM sleep latencies. In the light phase, the number of waking episodes tended to decline, and wake episode duration elevated. However, these indicators presented the opposite tendency during the dark phase. Melatonin showed significant efficacy for ameliorating the sleep disorder and restoring physiological sleep, and most of the beneficial effect of melatonin was antagonized by luzindole, a melatonin receptor antagonist.

The darkness and the light: diurnal rodent models for seasonal affective disorder

The development of animal models is a critical step for exploring the underlying pathophysiological mechanisms of major affective disorders and for evaluating potential therapeutic approaches. Although most neuropsychiatric research is performed on nocturnal rodents, differences in how diurnal and nocturnal animals respond to changing photoperiods, combined with a possible link between circadian rhythm disruption and affective disorders, has led to a call for the development of diurnal animal models. The need for diurnal models is most clear for seasonal affective disorder (SAD), a widespread recurrent depressive disorder that is linked to exposure to short photoperiods. Here, we briefly review what is known regarding the etiology of SAD and then examine progress in developing appropriate diurnal rodent models. Although circadian disruption is often invoked as a key contributor to SAD, a mechanistic understanding of how misalignment between endogenous circadian physiology and daily environmental rhythms affects mood is lacking. Diurnal rodents show promise as models of SAD, as changes in affective-like behaviors are induced in response to short photoperiods or dim-light conditions, and symptoms can be ameliorated by brief exposure to intervals of bright light coincident with activity onset. One exciting avenue of research involves the orexinergic system, which regulates functions that are disturbed in SAD, including sleep cycles, the reward system, feeding behavior, monoaminergic neurotransmission and hippocampal neurogenesis. However, although diurnal models make intuitive sense for the study of SAD and are more likely to mimic circadian disruption, their utility is currently hampered by a lack of genomic resources needed for the molecular interrogation of potential mechanisms.

Meta-analysis of light and circadian timekeeping in rodents

We conducted a meta-analysis of papers published over the past half-century (1964-2017) that quantified the phase-shifting effects of timed light exposure on rodent locomotor rhythms. Descriptive statistics were tabulated in order to explore the extent to which these studies were generalizable across species, sex, age, circadian timing, and light sources. Attempts at understanding photic resetting were primarily targeted at younger male animals, with particular emphases placed on characterizing the pacemaker systems of C57BL/6 mice and Syrian hamsters during the parts of their subjective night most sensitive to delivery of white-fluorescent light. With subsequent analyses restricted to these rodent models, we then assessed the relationship between luminous exposure (via broadspectrum emission) and phase-shifting through a series of linear regressions. Monotonically increasing illuminance-response functions were noted at most circadian times surveyed. In the aggregate, our results show that previous research conducted on light's regulation of circadian timekeeping has been skewed in design with respect to several important biological variables. This bias might limit translation of phototherapy-relevant data to women and older individuals.

Non‐24‐hour sleep‐wake disorder successfully treated with the combination of ramelteon and suvorexant in a case of autism spectrum disorder

Introduction

Non‐24‐hour sleep‐wake disorder (N24SWD) is often observed in the visually impaired and those who isolate indoors. Melatonin receptor agonists may be used for treatment, but there is currently no evidence that they are effective in patients without visual impairment.

Case

We report a case of a 23‐year‐old woman who withdrew from her social life owing to autism spectrum disorder and experienced an unusual sleep rhythm. She presented with N24SWD. The N24SWD cycle averaged 25.6 days but was extended to 42 days using ramelteon. However, this was not enough. We prescribed the addition of suvorexant and the sleep cycle returned to normal.

Conclusion

N24SWD is a disease that seriously impairs social life and productivity. We propose a possible treatment strategy for N24SWD using ramelteon and suvorexant.

We present a case in which the combination therapy of ramelteon and suvorexant was effective for a patient with autism spectrum disorder with non‐24‐hour sleep‐wake disorder (N24SWD) owing to social withdrawal. Here, we discussed the pharmacological mechanism of the combination of ramelteon and suvorexant as a possible therapeutic strategy for patients with N24SWD.

Melatonin recovers sleep phase delayed by MK-801 through the melatonin MT2 receptor- Ca2+ -CaMKII-CREB pathway in the ventrolateral preoptic nucleus

Melatonin (MLT) is widely used to treat sleep disorders although the underlying mechanism is still elusive. In mice, using wheel-running detection, we found that exogenous MLT could completely recover the period length prolonged by N-methyl-D-aspartate receptor (NMDAR) impairment due to the injection of the NMDAR antagonist MK-801, a preclinical model of psychosis. The analysis of the possible underlying mechanisms indicated that MLT could regulate the homeostatic state in the ventrolateral preoptic nucleus (VLPO) instead of the circadian process in the suprachiasmatic nucleus (SCN). In addition, our data showed that MK-801 decreased Ca²⁺ -related CaMKII expression and CREB phosphorylation levels in the VLPO, and MLT could rescue these intracellular impairments but not NMDAR expression levels. Accordingly, Gcamp6 AAV virus was injected in-vivo to further monitor intracellular Ca²⁺ levels in the VLPO, and MLT demonstrated a unique ability to increase Ca²⁺ fluorescence compared with MK-801-injected mice. Additionally, using the selective melatonin MT₂ receptor antagonist 4-phenyl-2-propionamidotetralin (4P-PDOT), we discovered that the pharmacological effects of MLT upon NMDAR impairments were mediated by melatonin MT₂ receptors. Using electroencephalography/electromyography (EEG/EMG) recordings, we observed that the latency to the first nonrapid eye movement (NREM) sleep episode was delayed by MK-801, and MLT was able to recover this delay. In conclusion, exogenous MLT by acting upon melatonin MT₂ receptors rescues sleep phase delayed by NMDAR impairment via increasing intracellular Ca²⁺ signaling in the VLPO, suggesting a regulatory role of the neurohormone on the homeostatic system.

KLF4 Exerts Sedative Effects in Pentobarbital-Treated Mice

KLF4 is a zinc-finger transcription factor that plays an essential role in many biological processes, including neuroinflammation, neuron regeneration, cell proliferation, and apoptosis. Through effects on these processes, KLF4 has likely roles in Alzheimer's disease, Parkinson's disease, and traumatic brain injury. However, little is known about the role of KLF4 in more immediate behavioral processes that similarly depend upon broad changes in brain excitability, such as the sleep process. Here, behavioral approaches, western blot, and immunohistochemical experiments were used to explore the role of KLF4 on sedation and the potential mechanisms of those effects. The results showed that overexpression of KLF4 prolonged loss of righting reflex (LORR) duration in pentobarbital-treated mice and increased c-Fos expression in the lateral hypothalamus (LH) and the ventrolateral preoptic nucleus (VLPO), while it decreased c-Fos expression in the tuberomammillary nucleus (TMN). Moreover, overexpression of KLF4 reduced the expression of p53 in the hypothalamus and increased the expression of STAT3 in the hypothalamus. Therefore, these results suggest that KLF4 exerts sedative effects through the regulation of p53 and STAT3 expression, and it indicates a role of KLF4 ligands in the treatment of sleep disorders.

Utilizing Melatonin to Alleviate Side Effects of Chemotherapy: A Potentially Good Partner for Treating Cancer with Ageing

Persistent senescence seems to exert detrimental effects fostering ageing and age-related disorders, such as cancer. Chemotherapy is one of the most valuable treatments for cancer, but its clinical application is limited due to adverse side effects. Melatonin is a potent antioxidant and antiageing molecule, is nontoxic, and enhances the efficacy and reduces the side effects of chemotherapy. In this review, we first summarize the mitochondrial protective role of melatonin in the context of chemotherapeutic drug-induced toxicity. Thereafter, we tabulate the protective actions of melatonin against ageing and the harmful roles induced by chemotherapy and chemotherapeutic agents, including anthracyclines, alkylating agents, platinum, antimetabolites, mitotic inhibitors, and molecular-targeted agents. Finally, we discuss several novel directions for future research in this area. The information compiled in this review will provide a comprehensive reference for the protective activities of melatonin in the context of chemotherapy drug-induced toxicity and will contribute to the design of future studies and increase the potential of melatonin as a therapeutic agent.

Multiple Sclerosis: Melatonin, Orexin, and Ceramide Interact with Platelet Activation Coagulation Factors and Gut-Microbiome-Derived Butyrate in the Circadian Dysregulation of Mitochondria in Glia and Immune Cells

Recent data highlight the important roles of the gut microbiome, gut permeability, and alterations in mitochondria functioning in the pathophysiology of multiple sclerosis (MS). This article reviews such data, indicating two important aspects of alterations in the gut in the modulation of mitochondria: (1) Gut permeability increases toll-like receptor (TLR) activators, viz circulating lipopolysaccharide (LPS), and exosomal high-mobility group box (HMGB)1. LPS and HMGB1 increase inducible nitric oxide synthase and superoxide, leading to peroxynitrite-driven acidic sphingomyelinase and ceramide. Ceramide is a major driver of MS pathophysiology via its impacts on glia mitochondria functioning; (2) Gut dysbiosis lowers production of the short-chain fatty acid, butyrate. Butyrate is a significant positive regulator of mitochondrial function, as well as suppressing the levels and effects of ceramide. Ceramide acts to suppress the circadian optimizers of mitochondria functioning, viz daytime orexin and night-time melatonin. Orexin, melatonin, and butyrate increase mitochondria oxidative phosphorylation partly via the disinhibition of the pyruvate dehydrogenase complex, leading to an increase in acetyl-coenzyme A (CoA). Acetyl-CoA is a necessary co-substrate for activation of the mitochondria melatonergic pathway, allowing melatonin to optimize mitochondrial function. Data would indicate that gut-driven alterations in ceramide and mitochondrial function, particularly in glia and immune cells, underpin MS pathophysiology. Aryl hydrocarbon receptor (AhR) activators, such as stress-induced kynurenine and air pollutants, may interact with the mitochondrial melatonergic pathway via AhR-induced cytochrome P450 (CYP)1b1, which backward converts melatonin to N-acetylserotonin (NAS). The loss of mitochnodria melatonin coupled with increased NAS has implications for altered mitochondrial function in many cell types that are relevant to MS pathophysiology. NAS is increased in secondary progressive MS, indicating a role for changes in the mitochondria melatonergic pathway in the progression of MS symptomatology. This provides a framework for the integration of diverse bodies of data on MS pathophysiology, with a number of readily applicable treatment interventions, including the utilization of sodium butyrate.

Sleep well. Untangling the role of melatonin MT1 and MT2 receptors in sleep

The pharmacological potential of targeting selectively melatonin MT1 or MT2 receptors has not yet been exploited in medicine. Research using selective MT1/MT2 receptor ligands and MT1/MT2 receptor knockout mice has indicated that the activation of MT2 receptors selectively increases non-rapid eye movement (NREM) sleep whereas MT1 receptors seem mostly implicated in the regulation of REM sleep. Moreover, MT1 knockout mice show an increase in NREM sleep, while MT2 knockout a decrease, suggesting an opposite role of these two receptors. A recent paper in mice by Sharma et al (J Pineal Res, 2018, e12498) found that MT1 but not MT2 receptors are expressed on orexin neurons in the perifornical lateral hypothalamus (PFH). Moreover, after injecting melatonin or luzindole into the mouse PFH, the authors suggest that melatonin promotes NREM sleep because activates PFH MT1 receptors, which in turn inhibit orexin neurons that are important in promoting arousal and maintaining wakefulness. In this commentary, we have critically commented on some of these findings on the bases of previous literature. In addition, we highlighted the fact that no conclusions could be drawn on the melatonin receptor subtype mediating the effects of melatonin on sleep because the authors used the non-selective MT1/MT2 receptors antagonist luzindole. More solid research should further characterize the pharmacological function of these two melatonin receptors in sleep.

Is circadian rhythmicity a prerequisite to coma recovery? Circadian recovery concomitant to cognitive improvement in two comatose patients

Circadian rhythmicity (CR) is involved in the regulation of all integrated functions, from sleep-wake cycle regulation to metabolic function, mood and cognition. However, the interdependence of CR, cognition and consciousness has been poorly addressed. To clarify the state of CR in coma and to determine the chronological relationship between its recovery and consciousness after brain lesions, we conducted a longitudinal observational study investigating how the state of CR was chronologically related with the recovery of behavioural wakefulness, cognition and/or awareness. Among 16 acute comatose patients, we recruited two 37-year-old patients with a persistent disorder of consciousness, presenting diencephalic lesions caused by severe traumatic brain injuries. Two biological urinary markers of CR were explored every 2 hours during 24 hours (6-sulfatoxymelatonin, free cortisol) with a dedicated methodology to extract the endogenous component of rhythmicity (environmental light recording, near-constant-routine protocol, control of beta-blockers). They presented an initial absence of rhythmic secretions and a recovered CR 7-8 months later. This recovery was not associated with the restoration of behavioural wakefulness, but with an improvement of cognition and awareness (up to the minimally conscious state). MRI showed a lesion pattern compatible with the interruption of either the main hypothalamic-sympathetic pathway or the accessory habenular pathway. These results suggest that CR may be a prerequisite for coma recovery with a potential but still unproven favourable effect on brain function of the resorted circadian melatonin secretion and/or the functional recovery of the suprachiasmatic nucleus (SCN). Assessing circadian functions by urinary melatonin should be further explored as a biomarker of cognition reappearance and investigated to prognosticate functional recovery.

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

The pathophysiological function of the G-protein coupled melatonin MT1 and MT2 receptors has not yet been well-clarified. Recent advancements using selective MT1/ MT2 receptor ligands and MT1/MT2 receptor knockout mice have suggested that the activation of the MT1 receptors are mainly implicated in the regulation of rapid eye movement (REM) sleep, whereas the MT2 receptors selectively increase non-REM (NREM) sleep. Studies in mutant mice show that MT1 knockout mice have an increase in NREM sleep and a decrease in REM sleep, while MT2 knockout mice a decrease in NREM sleep. The localization of MT1 receptors is also distinct from MT2 receptors; for example, MT2 receptors are located in the reticular thalamus (NREM area), while the MT1 receptors in the Locus Coeruleus and lateral hypothalamus (REM areas). Altogether, these findings suggest that these two receptors not only have a very specialized function in sleep, but that they may also modulate opposing effects. These data also suggest that mixed MT1-MT2 receptors ligands are not clinically recommended given their opposite roles in physiological functions, confirmed by the modest effects of melatonin or MT1/MT2 non-selective agonists when used in both preclinical and clinical studies as hypnotic drugs. In sum, MT1 and MT2 receptors have specific roles in the modulation of sleep, and consequently, selective ligands with agonist, antagonist, or partial agonist properties could have therapeutic potential for sleep; while the MT2 agonists or partial agonists might be indicated for NREM-related sleep and/or anxiety disorders, the MT1 agonists or partial agonists might be so for REM-related sleep disorders. Furthermore, MT1 but not MT2 receptors seem involved in the regulation of the circadian rhythm. Future research will help further develop MT1 and/or MT2 receptors as targets for neuropsychopharmacology drug development.