Melatonin: exceeding expectations

Effect of mesenchymal stem cells and melatonin on experimentally induced peripheral nerve injury in rats

Injury of a peripheral nerve (PNI) leads to both ischemic and inflammatory alterations. Sciatic nerve injury (SNI) represents the most widely used model for PNI. Mesenchymal stem cell-based therapy (MSCs) has convenient properties on PNI by stimulating the nerve regeneration. Melatonin has cytoprotective activity. The neuroprotective characteristics of MSCs and melatonin separately or in combination remain a knowledge need. In the rats-challenged SNI, therapeutic roles of intralesional MSCs and intraperitoneal melatonin injections were evaluated by functional assessment of peripheral nerve regeneration by walking track analysis involving sciatic function index (SFI) and two electrophysiological tests, electromyography and nerve conduction velocity, as well as measurement of antioxidant markers in serum, total antioxidant capacity (TAC) and malondialdehyde, and mRNA expression of brain derived neurotrophic factor (BDNF) in nerve tissues in addition to the histopathological evaluation of nerve tissue. Both individual and combination therapy with MSCs and melatonin therapies could effectively ameliorate this SNI and promote its regeneration as evidenced by improving the SFI and two electrophysiological tests and remarkable elevation of TAC with decline in lipid peroxidation and upregulation of BDNF levels. All of these led to functional improvement of the damaged nerve tissues and good recovery of the histopathological sections of sciatic nerve tissues suggesting multifactorial synergistic approach of the concurrent usage of melatonin and MSCs in PNI. The combination regimen has the most synergistic neuro-beneficial effects in PNI that should be used as therapeutic option in patients with PNI to boost their quality of life.

Protective effect of melatonin against metabolic disorders and neuropsychiatric injuries in type 2 diabetes mellitus mice

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by hyperglycemia and progressive cognitive dysfunction, and our clinical investigation revealed that the plasma concentration of melatonin (Mlt) decreased and was closely related to cognition in T2DM patients. However, although many studies have suggested that Mlt has a certain protective effect on glucose and lipid metabolism disorders and neuropsychiatric injury, the underlying mechanism of Mlt against T2DM-related metabolic and cognitive impairments remains unclear.

PURPOSE

The aim of the present study was to investigate the therapeutic effect of Mlt on metabolic disorders and Alzheimer's disease (AD)-like neuropsychiatric injuries in T2DM mice and to explore the possible underlying molecular mechanism involved.

METHODS

A T2DM mouse model was established by a combination of a high-fat diet (HFD) and streptozotocin (STZ, 100 mg/kg, i.p.), and Mlt (5, 10 or 20 mg/kg) was intragastrically administered for six consecutive weeks. The serum levels of glycolipid metabolism indicators were measured, behavioral performance was tested, and the protein expression of key molecules involved in the regulation of synaptic plasticity, circadian rhythms, and neuroinflammation in the hippocampus was detected. Moreover, the fluorescence intensities of glial fibrillary acidic protein (GFAP), ionized calcium binding adapter molecule 1 (IBA-1), amyloid β-protein (Aβ) and phosphorylated Tau (p-Tau) in the hippocampus were also observed.

RESULTS

Treatment with Mlt not only improved T2DM-related metabolic disorders, as indicated by increased serum concentrations of fasting blood glucose (FBG), glycosylated hemoglobin (HbAlc), insulin (INS), total cholesterol (TC) and triglyceride (TG), improved glucose tolerance and liver and pancreas function but also alleviated AD-like neuropsychiatric injuries in a HFD/STZ-induced mouse model, as indicated by decreased immobility time in the tail suspension test (TST) and forced swimming test (FST), increased preference indices of novel objects or novel arms in the novel object recognition test (NOR) and Y-maze test (Y-maze), and improved platform positioning capability in the Morris water maze (MWM) test. Moreover, treatment with Mlt also improved the hyperactivation of astrocytes and microglia in the hippocampus of mice, accompanied by reduced expression of interleukin 1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor (TNF-α), Aβ, and p-Tau and increased expression of brain-derived neurotrophic factor (BDNF), Synapsin I, Synaptotagmin I, melatonin receptor 1B (MT1B), brain muscle arnt-like protein 1 (Bmal1), circadian locomotor output cycles kaput (Clock), period 2 (Per2), and cryptochrome 2 (Cry2).

CONCLUSION

Mlt alleviated T2DM-related metabolic disorders and AD-like neuropsychiatric injuries in a HFD/STZ-induced mouse model, possibly through a mechanism involving the regulation of glial activation and associated neuroinflammation and the balancing of synaptic plasticity and circadian rhythms in the hippocampus.

Melatonin reduces oxidative stress and improves follicular morphology in feline (Felis catus) vitrified ovarian tissue

Ovarian tissue vitrification is associated with multiple events that promote accumulation of ROS (reactive oxygen species) which culminate in follicular apoptosis. Thus, this study was aimed at evaluating the role of melatonin in vitrification and culture of feline (Felis catus) ovarian tissue. In phase 1, domestic cat ovaries were fragmented into equal circular pieces of 1.5 mm diameter by 1 mm thickness and divided into four groups (fresh control and 3 treatments). The treatments were exposed to vitrification solutions supplemented with melatonin at 0 M, 10-9 M, and 10-7 M, then vitrified-warmed, histologically evaluated and assayed for ROS. Consequently, phase 2 experiment was designed wherein ovarian fragments were divided into two groups. One group was exposed to vitrification solution without melatonin and the other with 10-7 M melatonin supplementation, then vitrified-warmed and cultured for ten days with fresh ovarian fragments as control prior to assessment for histology, immunohistochemistry (Ki-67, MCM-7 and caspase-3) and ROS. Concentration of ROS was lower (p = 0.0009) in 10-7 M supplemented group in addition to higher proportion of grade 1 follicles. After culture, proportions of intact and activated follicles were higher (p < 0.05) in melatonin supplemented group evidenced by higher expression of Ki-67 and MCM-7. Follicular apoptosis was lower in melatonin supplemented group. In conclusion, melatonin at 10-7 M concentration preserved follicular morphological integrity while reducing ROS concentration in vitrified-warmed feline ovarian tissue. It has also promoted the follicular viability and activation with reduced apoptosis during in vitro culture of vitrified-warmed feline ovarian tissue.

Effect of melatonin supplementation on body composition and blood pressure in adults: A systematic review and Dose-Response meta-analysis of randomized controlled trial

Background

Several randomized controlled trials (RCTs) have explored the impact of melatonin on body composition and blood pressure (BP). However, the findings from these studies remain a topic of debate. This systematic review and meta-analysis of RCTs sought to evaluate the effects of melatonin consumption on body composition (body weight (BW), body mass index (BMI), waist circumference (WC), hip circumference (HC)) and asleep/daytime BP (systolic blood pressure (SBP) and diastolic blood pressure (DBP)) in adults.

Methods

In order to identify eligible RCTs, a systematic literature search was carried out up to June 2024 in PubMed, Embase, Scopus, and Web of Science without any language restrictions. The I2 statistic was used to perform heterogeneity tests on the selected studies. After evaluating random effects models based on heterogeneity tests, the weighted mean differences (WMD) with a 95 % confidence interval (CI) were calculated using pooled data.

Results

Overall, 28 studies (n = 1,543 participants) met our inclusion criteria. A pooled analysis of studies demonstrated that melatonin consumption led to a significant reduction in HC (WMD: 1.21 cm; 95 % CI: 1.94 to -0.49; P = 0.001), and daytime DBP (WMD: 1.40 mmHg; 95 % CI: 2.46 to -0.34; P = 0.009) in comparison with the control group. However, no substantial effects were observed on BW, BMI, WC, and SBP compared to the control group. Conclusion: The current meta-analysis of RCTs shows that treatment with melatonin reduces HC and daytime DBP levels in adults. However, further well-designed RCTs with large sample sizes and long durations are necessary to determine the effect of this supplement on body composition and BP.

Melatonin synergistically potentiates the effect of methylprednisolone on reducing neuroinflammation in the experimental autoimmune encephalomyelitis mouse model of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune neurodegenerative disease of unknown etiology characterized by infiltration of encephalitogenic cells in the central nervous system (CNS) resulting in the presence of multifocal areas of demyelination leading to neurodegeneration. The infiltrated immune cells population is composed mainly of effector CD4+ and CD8+ T lymphocytes, B cells, macrophages, and dendritic cells that secrete pro-inflammatory factors that eventually damage myelin leading to axonal damage. The most common clinical form of MS is relapsing-remitting (RR), characterized by neuroinflammatory episodes followed by partial or total recovery of neurological deficits. The first-line treatment for RRMS relapses is a high dose of glucocorticoids, especially methylprednisolone, for three to five consecutive days. Several studies have reported the beneficial effects of melatonin in the context of neuroinflammation associated with MS or experimental autoimmune encephalomyelitis (EAE), the preclinical model for MS. Therefore, the objective of this study was to evaluate the effect of the combined treatment of melatonin and methylprednisolone on the neuroinflammatory response associated with the EAE development. This study shows for the first time the protective synergistic effect of co-treatment with melatonin and methylprednisolone on reducing the severity of EAE by decreasing CD4 lymphocytes, B cells, macrophages and dendritic cells in the CNS, as well as modulating the population of infiltrated T and B cells toward regulatory phenotypes to the detriment of pro-inflammatory effector functions. In addition to the potentiation of the protective role of methylprednisolone, treatment with melatonin from the clinical onset of EAE improves the natural course of the EAE and the response to a subsequent treatment with methylprednisolone in a later relapse of the disease, pointing melatonin as potential therapeutic tool in combination with methylprednisolone for the treatment of relapses in MS.

Melatonin regulates endoplasmic reticulum stress in diverse pathophysiological contexts: A comprehensive mechanistic review

The endoplasmic reticulum (ER) is crucial for protein quality control, and disruptions in its function can lead to various diseases. ER stress triggers an adaptive response called the unfolded protein response (UPR), which can either restore cellular homeostasis or induce cell death. Melatonin, a safe and multifunctional compound, shows promise in controlling ER stress and could be a valuable therapeutic agent for managing the UPR. By regulating ER and mitochondrial functions, melatonin helps maintain cellular homeostasis via reduction of oxidative stress, inflammation, and apoptosis. Melatonin can directly or indirectly interfere with ER-associated sensors and downstream targets of the UPR, impacting cell death, autophagy, inflammation, molecular repair, among others. Crucially, this review explores the mechanistic role of melatonin on ER stress in various diseases including liver damage, neurodegeneration, reproductive disorders, pulmonary disease, cardiomyopathy, insulin resistance, renal dysfunction, and cancer. Interestingly, while it alleviates the burden of ER stress in most pathological contexts, it can paradoxically stimulate ER stress in cancer cells, highlighting its intricate involvement in cellular homeostasis. With numerous successful studies using in vivo and in vitro models, the continuation of clinical trials is imperative to fully explore melatonin's therapeutic potential in these conditions.

Melatonin as a Circadian Marker for Plasmodium Rhythms

Plasmodium, a digenetic parasite, requires a host and a vector for its life cycle completion. Most Plasmodium species display circadian rhythmicity during their intraerythrocytic cycle within the host, aiding in immune evasion. This rhythmicity, however, diminishes in in vitro cultures, highlighting the importance of host-derived signals for synchronizing the parasite's asexual cycle. Studies indicate a species-specific internal clock in Plasmodium, dependent on these host signals. Melatonin, a hormone the pineal gland produces under circadian regulation, impacts various physiological functions and is extensively reviewed as the primary circadian marker affecting parasite rhythms. Research suggests that melatonin facilitates synchronization through the PLC-IP3 signaling pathway, activating phospholipase C, which triggers intracellular calcium release and gene expression modulation. This evidence strongly supports the role of melatonin as a key circadian marker for parasite synchronization, presenting new possibilities for targeting the melatonin pathway when developing novel therapeutic approaches.

Melatonin and Vascular Function

The indolamine hormone melatonin, also known as N-acetyl-5-methoxytrypamine, is frequently associated with circadian rhythm regulation. Light can suppress melatonin secretion, and photoperiod regulates melatonin levels by promoting its production and secretion at night in response to darkness. This hormone is becoming more and more understood for its functions as an immune-modulatory, anti-inflammatory, and antioxidant hormone. Melatonin may have a major effect on several diabetes-related disturbances, such as hormonal imbalances, oxidative stress, sleep disturbances, and mood disorders, according to recent research. This has raised interest in investigating the possible therapeutic advantages of melatonin in the treatment of diabetic complications. In addition, several studies have described that melatonin has been linked to the development of diabetes, cancer, Alzheimer's disease, immune system disorders, and heart diseases. In this review, we will highlight some of the functions of melatonin regarding vascular biology.

Pyroptosis mediates osteoporosis via the inflammation immune microenvironment

Osteoporosis represents a systemic imbalance in bone metabolism, augmenting the susceptibility to fractures among patients and emerging as a notable mortality determinant in the elderly population. It has evolved into a worldwide concern impacting the physical well-being of the elderly, imposing a substantial burden on both human society and the economy. Presently, the precise pathogenesis of osteoporosis remains inadequately characterized and necessitates further exploration. The advancement of osteoporosis is typically linked to the initiation of an inflammatory response. Cells in an inflammatory environment can cause inflammatory death including pyroptosis. Pyroptosis is a recently identified form of programmed cell death with inflammatory properties, mediated by the caspase and gasdermin families. It is regarded as the most inflammatory form of cell death in contemporary medical research. Under the influence of diverse cytokines, macrophages, and other immune cells may undergo pyroptosis, releasing inflammatory factors, such as IL-1β and IL-18. Numerous lines of evidence highlight the pivotal role of pyroptosis in the pathogenesis of inflammatory diseases, including cancer, intestinal disorders, hepatic conditions, and cutaneous ailments. Osteoporosis progression is frequently associated with inflammation; hence, pyroptosis may also play a role in the pathogenesis of osteoporosis to a certain extent, making it a potential target for treatment. This paper has provided a comprehensive summary of pertinent research concerning pyroptosis and its impact on osteoporosis. The notion proposing that pyroptosis mediates osteoporosis via the inflammatory immune microenvironment is advanced, and we subsequently investigate potential targets for treating osteoporosis through the modulation of pyroptosis.

Arrestin beta-2 deficiency exacerbates periodontal inflammation by mediating activating transcription factor 6 activation and abnormal remodelling of the extracellular matrix

AIM

To investigate the specific role of arrestin beta-2 (ARRB2) in the progression of periodontitis and the underlying mechanisms.

MATERIALS AND METHODS

Single-cell RNA sequencing data were used to analyse gene expression in periodontal tissues from healthy controls and patients with periodontitis. Real-time quantitative polymerase chain reaction, Western blotting and immunohistochemical staining were performed to detect the expression of ARRB2. Furthermore, a ligature-induced periodontitis model was created. Using radiographic and histological methods, RNA sequencing and luciferase assay, the role of ARRB2 in periodontitis and the underlying mechanisms were explored. Finally, the therapeutic effect of melatonin, an inhibitor of activating transcription factor 6 (ATF6), on periodontitis in mice was assessed in both in vivo and in vitro experiments.

RESULTS

ARRB2 expression was up-regulated in inflammatory periodontal tissue. In the ligature-induced mouse model, Arrb2 knockout exacerbated alveolar bone loss (ABL) and extracellular matrix (ECM) degradation. ARRB2 exerted a negative regulatory effect on ATF6, an essential targeted gene. Melatonin ameliorated ABL and an imbalance in ECM remodelling in Arrb2-deficient periodontitis mice.

CONCLUSIONS

ARRB2 mediates ECM remodelling via inhibition of the ATF6 signalling pathway, which ultimately exerts a protective effect on periodontal tissues.

Melatonin suppresses atherosclerosis by ferroptosis inhibition via activating NRF2 pathway

Melatonin (MLT), a conserved small indole compound, exhibits anti-inflammatory and antioxidant properties, contributing to its cardioprotective effects. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is associated with atherosclerosis disease risk, and is known as an atherosclerosis risk biomarker. This study aimed to investigate the impact of MLT on Lp-PLA2 expression in the atherosclerotic process and explore the underlying mechanisms involved. In vivo, ApoE-/- mice were fed a high-fat diet, with or without MLT administration, after which the plaque area and collagen content were assessed. Macrophages were pretreated with MLT combined with ox-LDL, and the levels of ferroptosis-related proteins, NRF2 activation, mitochondrial function, and oxidative stress were measured. MLT administration significantly attenuated atherosclerotic plaque progression, as evidenced by decreased plaque area and increased collagen. Compared with those in the high-fat diet (HD) group, the levels of glutathione peroxidase 4 (GPX4) and SLC7A11 (xCT, a cystine/glutamate transporter) in atherosclerotic root macrophages were significantly increased in the MLT group. In vitro, MLT activated the nuclear factor-E2-related Factor 2 (NRF2)/SLC7A11/GPX4 signaling pathway, enhancing antioxidant capacity while reducing lipid peroxidation and suppressing Lp-PLA2 expression in macrophages. Moreover, MLT reversed ox-LDL-induced ferroptosis, through the use of ferrostatin-1 (a ferroptosis inhibitor) and/or erastin (a ferroptosis activator). Furthermore, the protective effects of MLT on Lp-PLA2 expression, antioxidant capacity, lipid peroxidation, and ferroptosis were decreased in ML385 (a specific NRF2 inhibitor)-treated macrophages and in AAV-sh-NRF2 treated ApoE-/- mice. MLT suppresses Lp-PLA2 expression and atherosclerosis processes by inhibiting macrophage ferroptosis and partially activating the NRF2 pathway.

Melatonin improves salivary gland damage and hypofunction in pSS by inhibiting IL-6/STAT3 signaling through its receptor-dependent manner

OBJECTIVE

Primary Sjogren's syndrome (pSS) is an autoimmune disease of the exocrine glands with no specific or efficient treatments. Melatonin, a natural hormone, is revealed to show multiple biological functions, both receptor-dependent and independent effects, including anti-apoptotic, antioxidant, and anti-inflammatory activities. However, the potential mechanism by which melatonin protects salivary glands (SGs) of pSS from damage needs to be clarified. The purpose of current study was to explore the role and receptor-related mechanisms of melatonin in pSS-induced glandular damage.

METHODS AND RESULTS

NOD/Ltj mice were used to spontaneously mimic pSS-induced glandular hypofunction in vivo and primary human salivary gland epithelial (HSGE) cells were stimulated by interferon-γ (IFN-γ) to mimic pSS-induced inflammation in SGs cells in vitro. Melatonin-treated mice exhibited a significant reduction in SG injury of NOD/Ltj mice, which was accompanied by an increase in salivary flow rate, a decrease in inflammatory infiltration within the gland, and a suppression of oxidative stress indicators as well as cell apoptosis. Notably, both melatonin membrane receptors and nuclear receptors played an important role in the anti-apoptotic effects of melatonin on the SGs of NOD/Ltj mice. Furthermore, melatonin blocked the IL-6/STAT3 pathway through receptor-dependent manners in IFN-γ-stimulated HSGE cells. However, it was evident that the anti-oxidative and anti-apoptotic properties of melatonin on IFN-γ-stimulated HSGE cells were diminished by IL-6 treatment.

CONCLUSION

Melatonin had the potential to mitigate inflammation, oxidative stress, and apoptosis in SGs of pSS by inhibiting the IL-6/STAT3 pathway through receptor-dependent mechanisms. This intervention effectively prevented glandular damage and preserved functional integrity.

Inflammation-Responsive Cell Membrane-Camouflaged Nanoparticles against Liver Fibrosis via Regulating Endoplasmic Reticulum Stress and Oxidative Stress

Liver fibrosis represents a reversible stage of various chronic liver diseases that progresses to cirrhosis. This condition is characterized by an imbalance between tissue damage and repair, and the production of fibers in the liver exceeds their degradation. Oxidative stress (OS) resulting from tissue injury and endoplasmic reticulum stress (ERS) triggered by the overproduction of proteins are pivotal factors in liver fibrosis. Melatonin demonstrates the capability to neutralize free radicals, shielding cells from oxidative harm. It is also a specific inhibitor of the ERS receptor transcription activating factor 6 (ATF6), indicating its great potential in ameliorating liver fibrosis. However, its limited water solubility and oral bioavailability of under 15% present hurdles in achieving therapeutic blood concentrations for treating liver fibrosis. The PLGA@Melatonin is constructed by loading melatonin with poly (lactic-co-glycolic acid) (PLGA). Platelet membranes (PM) and activated hepatic stellate cell membranes (HSCM) with high expression of the platelet-derived growth factor receptor (PDGFR) are extracted to successfully construct PM@PLGA@Melatonin and HSCM@PLGA@Melatonin, which are subsequently utilized to treat mice with liver fibrosis. The results illustrated the remarkable therapeutic effects of the two nanoparticles on liver fibrosis, along with their excellent targeting and biosafety properties.

Melatonin: a ferroptosis inhibitor with potential therapeutic efficacy for the post-COVID-19 trajectory of accelerated brain aging and neurodegeneration

The unprecedented pandemic of COVID-19 swept millions of lives in a short period, yet its menace continues among its survivors in the form of post-COVID syndrome. An exponentially growing number of COVID-19 survivors suffer from cognitive impairment, with compelling evidence of a trajectory of accelerated aging and neurodegeneration. The novel and enigmatic nature of this yet-to-unfold pathology demands extensive research seeking answers for both the molecular underpinnings and potential therapeutic targets. Ferroptosis, an iron-dependent cell death, is a strongly proposed underlying mechanism in post-COVID-19 aging and neurodegeneration discourse. COVID-19 incites neuroinflammation, iron dysregulation, reactive oxygen species (ROS) accumulation, antioxidant system repression, renin-angiotensin system (RAS) disruption, and clock gene alteration. These events pave the way for ferroptosis, which shows its signature in COVID-19, premature aging, and neurodegenerative disorders. In the search for a treatment, melatonin shines as a promising ferroptosis inhibitor with its repeatedly reported safety and tolerability. According to various studies, melatonin has proven efficacy in attenuating the severity of certain COVID-19 manifestations, validating its reputation as an anti-viral compound. Melatonin has well-documented anti-aging properties and combating neurodegenerative-related pathologies. Melatonin can block the leading events of ferroptosis since it is an efficient anti-inflammatory, iron chelator, antioxidant, angiotensin II antagonist, and clock gene regulator. Therefore, we propose ferroptosis as the culprit behind the post-COVID-19 trajectory of aging and neurodegeneration and melatonin, a well-fitting ferroptosis inhibitor, as a potential treatment.

JM. Antioxidant Actions of Melatonin: A Systematic Review of Animal Studies

Melatonin is an indoleamine with crucial antioxidant properties that are used to combat inflammatory and neoplastic processes, as well as control transplants. However, the clinical applications of melatonin have not yet been fully consolidated in the literature and require in-depth analysis.

OBJECTIVES

This study reviewed the literature on the antioxidant properties of melatonin in rat models.

METHODS

We followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses and used the PubMed, LILACS, and Cochrane databases, Google Scholar, and article references, irrespective of publication time.

RESULTS

Ten articles involving 485 rats were selected, and the effects of melatonin on antioxidant markers were investigated. Melatonin increased superoxide dismutase in nine studies, glutathione peroxidase in seven studies, and catalase in five studies. In contrast, melatonin reduced glutathione in three studies and malonaldehyde in seven of eight studies.

CONCLUSION

Our findings suggest that melatonin effectively reduces oxidative stress.

A Clinical, Pharmacological, and Formulation Evaluation of Melatonin in the Treatment of Ocular Disorders-A Systematic Review

Melatonin's cytoprotective properties may have therapeutic implications in treating ocular diseases like glaucoma and age-related macular degeneration. Literature data suggest that melatonin could potentially protect ocular tissues by decreasing the production of free radicals and pro-inflammatory mediators. This study aims to summarize the screened articles on melatonin's clinical, pharmacological, and formulation evaluation in treating ocular disorders. The identification of relevant studies on the topic in focus was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines. The studies were searched in the following databases and web search engines: Pubmed, Scopus, Science Direct, Web of Science, Reaxys, Google Scholar, Google Patents, Espacenet, and Patentscope. The search time interval was 2013-2023, with the following keywords: melatonin AND ocular OR ophthalmic AND formulation OR insert AND disease. Our key conclusion was that using melatonin-loaded nano-delivery systems enabled the improved permeation of the molecule into intraocular tissues and assured controlled release profiles. Although preclinical studies have demonstrated the efficacy of developed formulations, a considerable gap has been observed in the clinical translation of the results. To overcome this failure, revising the preclinical experimental phase might be useful by selecting endpoints close to clinical ones.

Melatonin: A look at protozoal and helminths

Melatonin is a pleiotropic neurohormone found in different animal, plant, and microorganism species. It is a product resulting from tryptophan metabolism in the pineal gland and is widely known for its ability to synchronize the circadian rhythm to antitumor functions in different types of cancers. The molecular mechanisms responsible for its immunomodulatory, antioxidant and cytoprotective effects involve binding to high-affinity G protein-coupled receptors and interactions with intracellular targets that modulate signal transduction pathways. In vitro and in vivo studies have reported the therapeutic potential of melatonin in different infectious and parasitic diseases. In this review, the protective and pathophysiological roles of melatonin in fighting protozoan and helminth infections and the possible mechanisms involved against these stressors will be discussed.

Melatonin increased antioxidant capacity to ameliorate growth retardation and intestinal epithelial barrier dysfunction in diquat-challenged piglets

BACKGROUND

Diquat is a common environmental pollutant, which can cause oxidative stress in humans and animals. Diquat exposure causes growth retardation and intestinal damage. Therefore, this study was performed to investigate the effects of melatonin on diquat-challenged piglets.

RESULTS

Dietary supplementation with 2 mg kg-1 melatonin significantly increased the average daily gain and feed conversion rate in piglets. Melatonin increased antioxidant capacity, and improved intestinal epithelial barrier function of duodenum and jejunum in piglets. Moreover, melatonin was found to regulated the expression of immune and antioxidant-related genes. Melatonin also alleviated diquat-induced growth retardation and anorexia in diquat-challenged piglets. It also increased antioxidant capacity, and ameliorated diquat-induced intestinal epithelial barrier injury. Melatonin also regulated the expression of MnSOD and immuner-elated genes in intestinal.

CONCLUSION

Dietary supplementation with 2 mg kg-1 melatonin increased antioxidant capacity to ameliorate diquat-induced oxidative stress, alleviate intestinal epithelial barrier injury, and increase growth performance in weaned piglets. © 2023 Society of Chemical Industry.

Causal associations between modifiable risk factors and isolated REM sleep behavior disorder: a mendelian randomization study

Objectives

This Mendelian randomization (MR) study identified modifiable risk factors for isolated rapid eye movement sleep behavior disorder (iRBD).

Methods

Genome-wide association study (GWAS) datasets for 29 modifiable risk factors for iRBD in discovery and replication stages were used. GWAS data for iRBD cases were obtained from the International RBD Study Group. The inverse variance weighted (IVW) method was primarily employed to explore causality, with supplementary analyses used to verify the robustness of IVW findings. Co-localization analysis further substantiated causal associations identified via MR. Genetic correlations between mental illness and iRBD were identified using trait covariance, linkage disequilibrium score regression, and co-localization analyses.

Results

Our study revealed causal associations between sun exposure-related factors and iRBD. Utilizing sun protection (odds ratio [OR] = 0.31 [0.14, 0.69], p = 0.004), ease of sunburn (OR = 0.70 [0.57, 0.87], p = 0.001), childhood sunburn occasions (OR = 0.58 [0.39, 0.87], p = 0.008), and phototoxic dermatitis (OR = 0.78 [0.66, 0.92], p = 0.003) decreased iRBD risk. Conversely, a deep skin color increased risk (OR = 1.42 [1.04, 1.93], p = 0.026). Smoking, alcohol consumption, low education levels, and mental illness were not risk factors for iRBD. Anxiety disorders and iRBD were genetically correlated.

Conclusion

Our study does not corroborate previous findings that identified smoking, alcohol use, low education, and mental illness as risk factors for iRBD. Moreover, we found that excessive sun exposure elevates iRBD risk. These findings offer new insights for screening high-risk populations and devising preventive measures.

Receptor-Mediated and Receptor-Independent Actions of Melatonin in Vertebrates

Melatonin (N-acetyl-5-methoxytryptamine) is an indolamine that is synthesized from tryptophan in the pineal glands of vertebrates through four enzymatic reactions. Melatonin is a quite unique bioactive substance, characterized by a combination of both receptor-mediated and receptor-independent actions, which promote the diverse effects of melatonin. One of the main functions of melatonin, via its membrane receptors, is to regulate the circadian or seasonal rhythm. In mammals, light information, which controls melatonin synthesis, is received in the eye, and transmitted to the pineal gland, via the suprachiasmatic nucleus, where the central clock is located. Alternatively, in many vertebrates other than mammals, the pineal gland cells, which are involved in melatonin synthesis and secretion and in the circadian clock, directly receive light. Recently, it has been reported that melatonin possesses several metabolic functions, which involve bone and glucose, in addition to regulating the circadian rhythm. Melatonin improves bone strength by inhibiting osteoclast activity. It is also known to maintain brain activity during sleep by increasing glucose uptake at night, in an insulin-independent manner. Moreover, as a non-receptor-mediated action, melatonin has antioxidant properties. Melatonin has been proven to be a potent free radical scavenger and a broad-spectrum antioxidant, even protecting organisms against radiation from space. Melatonin is a ubiquitously distributed molecule and is found in bacteria, unicellular organisms, fungi, and plants. It is hypothesized that melatonin initially functioned as an antioxidant, then, in vertebrates, it combined this role with the ability to regulate rhythm and metabolism, via its receptors.

Melatonin alleviates valproic acid-induced neural tube defects by modulating Src/PI3K/ERK signaling and oxidative stress

Neural tube defects (NTDs) represent a developmental disorder of the nervous system that can lead to significant disability in children and impose substantial social burdens. Valproic acid (VPA), a widely prescribed first-line antiepileptic drug for epilepsy and various neurological conditions, has been associated with a 4-fold increase in the risk of NTDs when used during pregnancy. Consequently, urgent efforts are required to identify innovative prevention and treatment approaches for VPA-induced NTDs. Studies have demonstrated that the disruption in the delicate balance between cell proliferation and apoptosis is a crucial factor contributing to NTDs induced by VPA. Encouragingly, our current data reveal that melatonin (MT) significantly inhibits apoptosis while promoting the restoration of neuroepithelial cell proliferation impaired by VPA. Moreover, further investigations demonstrate that MT substantially reduces the incidence of neural tube malformations resulted from VPA exposure, primarily by suppressing apoptosis through the modulation of intracellular reactive oxygen species levels. In addition, the Src/PI3K/ERK signaling pathway appears to play a pivotal role in VPA-induced NTDs, with significant inhibition observed in the affected samples. Notably, MT treatment successfully reinstates Src/PI3K/ERK signaling, thereby offering a potential underlying mechanism for the protective effects of MT against VPA-induced NTDs. In summary, our current study substantiates the considerable protective potential of MT in mitigating VPA-triggered NTDs, thereby offering valuable strategies for the clinical management of VPA-related birth defects.

Exogenous melatonin induces salt and drought stress tolerance in rice by promoting plant growth and defense system

Due to global climate change, crops are certainly confronted with a lot of abiotic and biotic stress factors during their growth that cause a serious threat to their development and overall productivity. Among different abiotic stresses, salt and drought are considered the most devastating stressors with serious impact on crop's yield stability. Here, the current study aimed to elucidate how melatonin works in regulating plant biomass, oxidative stress, antioxidant defense system, as well as the expression of genes related to salt and drought stress in rice plants. Eight groups of rice plants (3 replicates, 5 plants each) underwent varied treatments: control, melatonin, salt, drought, salt + drought, salt + melatonin, drought + melatonin, and salt + drought + melatonin. Melatonin (100 µM) was alternately applied a week before stress exposure; salt stress received 100 mM NaCl every 3 days for 3 weeks, and drought stress involved 10% PEG. Young leaves were randomly sampled from each group. The results showed that melatonin treatment markedly reduces salt and drought stress damage by promoting root, shoot length, fresh and dry weight, increasing chlorophyll contents, and inhibiting excessive production of oxidative stress markers. Salt and drought stress significantly decreased the water balance, and damaged cell membrane by reducing relative water contents and increasing electrolyte leakage. However, melatonin treated rice plants showed high relative water contents and low electrolyte leakage. Under salt and drought stress conditions, exogenous application of melatonin boosted the expression level of salt and drought stress responsive genes like OsSOS, OsNHX, OsHSF and OsDREB in rice plants. Taken together, our results reveal that melatonin treatment significantly increases salt and drought tolerance of rice plants, by increasing plant biomass, suppressing ROS accumulation, elevating antioxidants defense efficiency, and up-regulating the expression of salt and drought stress responsive genes.

Melatonin: a modulator in metabolic rewiring in T-cell malignancies

Melatonin, (N-acetyl-5-methoxytryptamine) an indoleamine exerts multifaced effects and regulates numerous cellular pathways and molecular targets associated with circadian rhythm, immune modulation, and seasonal reproduction including metabolic rewiring during T cell malignancy. T-cell malignancies encompass a group of hematological cancers characterized by the uncontrolled growth and proliferation of malignant T-cells. These cancer cells exhibit a distinct metabolic adaptation, a hallmark of cancer in general, as they rewire their metabolic pathways to meet the heightened energy requirements and biosynthesis necessary for malignancies is the Warburg effect, characterized by a shift towards glycolysis, even when oxygen is available. In addition, T-cell malignancies cause metabolic shift by inhibiting the enzyme pyruvate Dehydrogenase Kinase (PDK) which in turn results in increased acetyl CoA enzyme production and cellular glycolytic activity. Further, melatonin plays a modulatory role in the expression of essential transporters (Glut1, Glut2) responsible for nutrient uptake and metabolic rewiring, such as glucose and amino acid transporters in T-cells. This modulation significantly impacts the metabolic profile of T-cells, consequently affecting their differentiation. Furthermore, melatonin has been found to regulate the expression of critical signaling molecules involved in T-cell activations, such as CD38, and CD69. These molecules are integral to T-cell adhesion, signaling, and activation. This review aims to provide insights into the mechanism of melatonin's anticancer properties concerning metabolic rewiring during T-cell malignancy. The present review encompasses the involvement of oncogenic factors, the tumor microenvironment and metabolic alteration, hallmarks, metabolic reprogramming, and the anti-oncogenic/oncostatic impact of melatonin on various cancer cells.

Function and Regulation of the Calcium-Activated Chloride Channel Anoctamin 1 (TMEM16A)

Various human tissues express the calcium-activated chloride channel Anoctamin 1 (ANO1), also known as TMEM16A. ANO1 allows the passive chloride flux that controls different physiological functions ranging from muscle contraction, fluid and hormone secretion, gastrointestinal motility, and electrical excitability. Overexpression of ANO1 is associated with pathological conditions such as hypertension and cancer. The molecular cloning of ANO1 has led to a surge in structural, functional, and physiological studies of the channel in several tissues. ANO1 is a homodimer channel harboring two pores - one in each monomer - that work independently. Each pore is activated by voltage-dependent binding of two intracellular calcium ions to a high-affinity-binding site. In addition, the binding of phosphatidylinositol 4,5-bisphosphate to sites scattered throughout the cytosolic side of the protein aids the calcium activation process. Furthermore, many pharmacological studies have established ANO1 as a target of promising compounds that could treat several illnesses. This chapter describes our current understanding of the physiological roles of ANO1 and its regulation under physiological conditions as well as new pharmacological compounds with potential therapeutic applications.

SerpinB1 is required for Rev-erbα-mediated protection against acute lung injury induced by lipopolysaccharide-in mice

BACKGROUND AND PURPOSE

Acute lung injury (ALI) is a serious, life-threatening inflammation of the lungs that still lacks effective treatment. We previously showed that serine protease inhibitor B1 (SerpinB1) protects against ALI induced by orthotopic autologous liver transplantation. However, the role of SerpinB1 in lipopolysaccharide (LPS)-induced ALI and its regulatory mechanisms are not known.

EXPERIMENTAL APPROACH

Wild-type (WT) and SerpinB1 knockout (KO) mice were treated with intratracheal LPS stimulation to induce ALI. Some of the WT and KO mice were injected i.p. with melatonin, a rhythm-related protein Rev-erbα agonist. The circadian rhythm in WT mice was disrupted by exposing mice to 24 h of continuous dark or light conditions after intratracheal LPS. Neutrophils were isolated from alveolar lavage fluid of WT and KO mice, and from human peripheral blood. Neutrophils were treated with LPS and melatonin.

KEY RESULTS

Disruption of circadian rhythm by either 24-h dark or light conditions exacerbated LPS-induced ALI and decreased expression of Rev-erbα and SerpinB1 protein in lung, whereas melatonin treatment increased SerpinB1 expression and attenuated LPS-induced ALI in WT mice, but not in KO mice. In isolated neutrophils, Rev-erbα was co-localized with SerpinB1 and bound to its promoter to trigger SerpinB1 transcription. Furthermore, LPS stimulation increased formation of neutrophil extracellular traps, which was reversed by melatonin treatment in neutrophils from WT mice, but not from KO mice.

CONCLUSION AND IMPLICATIONS

In mice, SerpinB1 is rhythmically regulated by Rev-erbα, and its down-regulation exacerbates LPS-induced ALI by inducing formation of neutrophil extracellular traps.

Melatonin Improves Mitochondrial Dysfunction and Attenuates Neuropathic Pain by Regulating SIRT1 in Dorsal Root Ganglions

Neuropathic pain is a debilitating chronic pain condition and is refractory to the currently available treatments. Emerging evidence suggests that melatonin exerts analgesic effects in rodent models of neuropathic pain. Nevertheless, the exact underlying mechanisms of the analgesic effects of melatonin on neuropathic pain are largely unknown. Here, we observed that spinal nerve ligation (SNL) in rats L5 and L6 induced an obvious decrease in the 50% paw withdrawal threshold (PWT) and paw withdrawal latency (PWL), indicating the induction of mechanical allodynia and the hyperalgesia, and melatonin prevented the genesis and maintenance of mechanical allodynia and the hyperalgesia. Notably, the inhibitory action of melatonin on SNL-induced mechanical allodynia and heat hypersensitivity was inhibited by a SIRT1 inhibitor (EX527). Melatonin treatment increased the expression of neuronal sirtuin1 (SIRT1) in DRGs following nerve injury. Furthermore, melatonin treatment restored the injury-dependent decrease in mitochondrial membrane potential and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and reduced the injury-dependent increase in hydrogen peroxide and 8-hydroxy-2-deoxyguanosine (8-OHdG), which was inhibited by EX527. In addition, we found that EX527 impeded the inhibitory effects of melatonin on the SNL-induced increased expression of cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). In conclusion, the above data demonstrated that melatonin alleviated mechanical allodynia and hyperalgesia induced by peripheral nerve injury via SIRT1 activation. Melatonin resolved mitochondrial dysfunction-oxidative stress-dependent and neuroinflammation mechanisms that were driven by SIRT1 after nerve injury.

Neuroprotective Potential of Melatonin: Evaluating Therapeutic Efficacy in Alzheimer's and Parkinson's Diseases

Decreased melatonin levels have been linked to both Alzheimer's disease (AD) and Parkinson's disease (PD), which are the two most prevalent neurodegenerative disorders. The development of sleep disorders is widespread in patients diagnosed with AD or PD. In this regard, calcification of the pineal gland, typically seen in the third decade, has been associated with a reduction in melatonin production. Recent studies have suggested that exogenous melatonin application can be utilized to treat sleep disorders in patients with neurodegenerative diseases. Furthermore, research has shown that deficiencies in melatonin levels in patients with AD or PD begin before a diagnosis of either disease is made. These findings could encourage further research on melatonin as a potential biomarker for the diagnosis or a possible area for the early treatment of these diseases. Many clinical studies have also produced data denoting melatonin treatment as a method to reduce the detrimental neurocognitive effects of these diseases. Further research on the role of melatonin in neurodegenerative diseases could expand symptomatic and prophylactic treatment options for diseases such as AD and PD. This review investigates melatonin's physiological properties, its role in AD and PD, and current findings on its potential therapeutic benefits in AD and PD patients.

Melatonin Exerts Prominent, Differential Epidermal and Dermal Anti-Aging Properties in Aged Human Eyelid Skin Ex Vivo

Human skin aging is associated with functional deterioration on multiple levels of physiology, necessitating the development of effective skin senotherapeutics. The well-tolerated neurohormone melatonin unfolds anti-aging properties in vitro and in vivo, but it remains unclear whether these effects translate to aged human skin ex vivo. We tested this in organ-cultured, full-thickness human eyelid skin (5-6 donors; 49-77 years) by adding melatonin to the culture medium, followed by the assessment of core aging biomarkers via quantitative immunohistochemistry. Over 6 days, 200 µM melatonin significantly downregulated the intraepidermal activity of the aging-promoting mTORC1 pathway (as visualized by reduced S6 phosphorylation) and MMP-1 protein expression in the epidermis compared to vehicle-treated control skin. Conversely, the transmembrane collagen 17A1, a key stem cell niche matrix molecule that declines with aging, and mitochondrial markers (e.g., TFAM, MTCO-1, and VDAC/porin) were significantly upregulated. Interestingly, 100 µM melatonin also significantly increased the epidermal expression of VEGF-A protein, which is required and sufficient for inducing human skin rejuvenation. In aged human dermis, melatonin significantly increased fibrillin-1 protein expression and improved fibrillin structural organization, indicating an improved collagen and elastic fiber network. In contrast, other key aging biomarkers (SIRT-1, lamin-B1, p16INK4, collagen I) remained unchanged. This ex vivo study provides proof of principle that melatonin indeed exerts long-suspected but never conclusively demonstrated and surprisingly differential anti-aging effects in aged human epidermis and dermis.

Adherence to treatment and parents' perspective about effectiveness of melatonin in children with autism spectrum disorder and sleep disturbances

OBJECTIVE

Melatonin is considered an effective pharmacological treatment for the sleep disturbances that are reported in > 50% of children with autism spectrum disorder (ASD). However, real-life data about the long-term course and effectiveness of melatonin treatment in children with ASD is lacking.

METHODS

In this retrospective cohort study, we assessed the adherence to melatonin treatment and parents' perspective of its effect on sleep quality and daytime behavior in children with ASD via a parental phone survey of children in the Azrieli National Center for Autism and Neurodevelopment Research (ANCAN) database. Cox regression analysis was used to assess the effect of key demographic and clinical characteristics on treatment adherence.

RESULTS

Melatonin was recommended for ~ 8% of children in the ANCAN database. These children were characterized by more severe symptoms of autism. The median adherence time for melatonin treatment exceeded 88 months, with the most common reason for discontinuation being a lack of effectiveness (14%). Mild side-effects were reported in 14% of children, and 86%, 54%, and 45% experienced improvements in sleep onset, sleep duration and night awakenings, respectively. Notably, melatonin also improved the daytime behaviors of > 28% of the children. Adherence to treatment was independently associated with improvements in night awakenings and educational functioning (aHR = 0.142, 95%CI = 0.036-0.565; and aHR = 0.195, 95%CI = 0.047-0.806, respectively).

CONCLUSIONS

Based on parents' report, melatonin is a safe and effective treatment that improves both sleep difficulties and daily behavior of children with ASD.

Non-Excitatory Amino Acids, Melatonin, and Free Radicals: Examining the Role in Stroke and Aging

The aim of this review is to explore the relationship between melatonin, free radicals, and non-excitatory amino acids, and their role in stroke and aging. Melatonin has garnered significant attention in recent years due to its diverse physiological functions and potential therapeutic benefits by reducing oxidative stress, inflammation, and apoptosis. Melatonin has been found to mitigate ischemic brain damage caused by stroke. By scavenging free radicals and reducing oxidative damage, melatonin may help slow down the aging process and protect against age-related cognitive decline. Additionally, non-excitatory amino acids have been shown to possess neuroprotective properties, including antioxidant and anti-inflammatory in stroke and aging-related conditions. They can attenuate oxidative stress, modulate calcium homeostasis, and inhibit apoptosis, thereby safeguarding neurons against damage induced by stroke and aging processes. The intracellular accumulation of certain non-excitatory amino acids could promote harmful effects during hypoxia-ischemia episodes and thus, the blockade of the amino acid transporters involved in the process could be an alternative therapeutic strategy to reduce ischemic damage. On the other hand, the accumulation of free radicals, specifically mitochondrial reactive oxygen and nitrogen species, accelerates cellular senescence and contributes to age-related decline. Recent research suggests a complex interplay between melatonin, free radicals, and non-excitatory amino acids in stroke and aging. The neuroprotective actions of melatonin and non-excitatory amino acids converge on multiple pathways, including the regulation of calcium homeostasis, modulation of apoptosis, and reduction of inflammation. These mechanisms collectively contribute to the preservation of neuronal integrity and functions, making them promising targets for therapeutic interventions in stroke and age-related disorders.

Melanogenesis Is Directly Affected by Metabolites of Melatonin in Human Melanoma Cells

Melatonin (N-acetyl-5-methoxytryptamine, MEL), its kynurenic (N1-acetyl-N2-formyl-5-methoxykynurenine, AFMK) and indolic derivatives (6-hydroxymelatonin, 6(OH)MEL and 5-methoxytryptamine, 5-MT) are endogenously produced in human epidermis. Melatonin, produced by the pineal gland, brain and peripheral organs, displays a diversity of physiological functions including anti-inflammatory, immunomodulatory, and anti-tumor capacities. Herein, we assessed their regulatory effect on melanogenesis using amelanotic (A375, Sk-Mel-28) and highly pigmented (MNT-1, melanotic) human melanoma cell lines. We discovered that subjected compounds decrease the downstream pathway of melanin synthesis by causing a significant drop of cyclic adenosine monophosphate (cAMP) level, the microphthalmia-associated transcription factor (MITF) and resultant collapse of tyrosinase (TYR) activity, and melanin content comparatively to N-phenylthiourea (PTU, a positive control). We observed a reduction in pigment in melanosomes visualized by the transmission electron microscopy. Finally, we assessed the role of G-protein-coupled seven-transmembrane-domain receptors. Obtained results revealed that nonselective MT1 and MT2 receptor antagonist (luzindole) or selective MT2 receptor antagonist (4-P-PDOT) did not affect dysregulation of the melanin pathway indicating a receptor-independent mechanism. Our findings, together with the current state of the art, provide a convenient experimental model to study the complex relationship between metabolites of melatonin and the control of pigmentation serving as a future and rationale strategy for targeted therapies of melanoma-affected patients.

Angiogenesis, coagulation, and fibrinolytic markers in acute promyelocytic leukemia (NB4): An evaluation of melatonin effects

Melatonin is a powerful biological agent that has been shown to inhibit angiogenesis and also exerts anti-inflammatory effects. It is well known that new blood vessel formation (angiogenesis) has become an urgent issue in leukemia as well as solid tumors. Acute promyelocytic leukemia (APL) is a form of liquid cancer that manifests increased angiogenesis in the bone marrow of patients. Despite high-rate curable treatment with all-trans-retinoic acid (ATRA) and recently arsenic-trioxide (ATO), early death because of hemorrhage, coagulopathy, and Disseminated intravascular coagulation (DIC) remains still a concerning issue in these patients. It is, therefore, urgent to seek treatment strategies with antiangiogenic capabilities that also diminish coagulopathy and hyperfibrinolysis in APL patients. In this study, a coculture system with human umbilical vein endothelial cells (HUVECs) and NB4 APL cells was used to investigate the direct effect of melatonin on angiogenesis and its possible action on tissue factor (TF) and tissue-type plasminogen activator-1 (TPA-1) expression. Our experiments revealed that HUVEC-induced angiogenesis by cocultured NB4 cells was suppressed when melatonin alone or in combination with ATRA was added to the incubation medium. Melatonin at concentrations of 1 mM inhibited tube formation of HUVECs and also decreased interleukin-6 secretion and VEGF mRNA expression in HUVEC and NB4 cells. Taken together, the results of this study demonstrate that melatonin inhibits accelerated angiogenesis of HUVECs and ameliorates the coagulation and fibrinolysis indices stimulated by coculturing with NB4 cells.

Molecular Insights into Antioxidant Efficiency of Melanin: A Sustainable Antioxidant for Natural Rubber Formulations

N-(1,3-Dimethyl butyl)-N'-phenyl-p-phenylenediamine (6-PPD) is a worldwide antioxidant commonly added to delay the thermo-oxidative degradation of tire rubbers. Unfortunately, 6PPD and its transformation product 6PPD-quinone are toxic to aquatic organisms (e.g., coho salmon). Herein, we explore the free radical scavenging activity and protective mechanism of melanin (MLN) on natural rubber's (NR's) oxidative resistance using molecular dynamics (MD) and quantum mechanical (QM) calculations. The relationship between the molecular structure and the chemical nature of the antioxidant molecules via transition state calculations is explored to unravel the reaction mechanisms of antioxidants interacting with peroxy radicals (ROO·) of NR with the estimation of reaction barriers. Following this, the radical scavenging activity of antioxidants was quantified via a hydrogen atom transfer mechanism and bond dissociation energy calculations. Parallel MD simulations were considered to study the interfacial interactions of antioxidant molecules with polymer chains and fillers with a quantifiable structure-property correlation. Given these results, the nanocomposite (NR-MLN-SiO2) with natural antioxidant melanin manifested outstanding antioxidant properties by preferentially bagging the ROO· radicals, thus improving NR's thermal-oxidative aging relative to 6-PPD. The MD results revealed that the intermolecular interactions at the NR/antioxidant interface benefited the antioxidant MLN to bind tightly to the NR in NR-MLN-SiO2 composite, thus exhibiting improved dispersion, O2 barrier properties, and thermo-oxidative stability, which could extend the service life of NR products (e.g., tires). In addition, as a sustainable antioxidant, MLN could replace toxic antioxidants like 6-PPD. More importantly, the QM/MD simulations provided a fundamental understanding of the mechanistic pathways of antioxidant molecules in NR composites, which are conducive to designing high-performance and sustainable green elastomers.

A new treatment approach: Melatonin and ascorbic acid synergy shields against sepsis-induced heart and kidney damage in male rats

AIM

To investigate the combined therapeutic potential of melatonin and ascorbic acid in mitigating sepsis-induced heart and kidney injury in male rats and assess the combination therapy's effects on inflammation, cellular damage, oxidative stress, and vascular function-related markers.

MATERIALS AND METHODS

Cecal ligation and puncture (CLP) induced sepsis in male rats, which were divided into five groups: Sham, CLP, MEL (melatonin), ASA (ascorbic acid), and MEL+ASA (melatonin and ascorbic acid). Rats were treated, and heart and kidney tissues were collected for biochemical and histopathological analyses. Inflammatory markers (presepsin, procalcitonin, NF-κB, IL-1β, IL-6, TNF-α), cellular damage marker (8-OHDG), oxidative status, nitric oxide (NO), vascular endothelial growth factor (VEGF), and sirtuin 1 (SIRT1) levels were assessed.

KEY FINDINGS

Melatonin and ascorbic acid treatment reduced inflammatory and cellular damage markers compared to the CLP group. Combined treatment improved NO, VEGF levels, and increased SIRT1 expression, suggesting a synergistic effect in mitigating sepsis-induced inflammation, cellular damage, and oxidative stress. Histopathological analyses supported these findings, revealing reduced heart and kidney injury in the MEL+ASA group.

SIGNIFICANCE

Our study highlights potential benefits of combining melatonin and ascorbic acid as a therapeutic strategy for alleviating sepsis-induced heart and kidney injury. The synergistic effects of these agents may provide stronger protection against inflammation, oxidative stress, and tissue damage, opening new avenues for future research and clinical applications in sepsis management.

Melatonin secretion patterns are associated with cognitive vulnerability and brain structure in bipolar depression

Circadian rhythm disruption is a core symptom of bipolar disorder (BD), also reflected in altered patterns of melatonin release. Reductions of grey matter (GM) volumes are well documented in BD. We hypothesized that levels and timing of melatonin secretion in bipolar depression could be associated with depressive psychopathology and brain GM integrity. The onset of melatonin secretion under dim light conditions (DLMO) and the amount of time between DLMO and midsleep (i.e. phase angle difference; PAD) were used as circadian rhythm markers. To study the time course of melatonin secretion, an exponential curve fitting the melatonin values was calculated, and the slope coefficients (SLP) were obtained for each participant. Significant differences were found between HC and BD in PAD measures and melatonin profiles. Correlations between PAD and depressive psychopathology were identified. Melatonin secretion patterns were found to be associated with GM volumes in the Striatum and Supramarginal Gyrus in BD. Our findings emphasized the role of melatonin secretion role as a biological marker of circadian synchronization in bipolar depression and provided a novel insight for a link between melatonin release and brain structure.

Melatonin enhances the developmental potential of immature oocytes from older reproductive-aged women by improving mitochondrial function

Aims

To evaluate whether melatonin (MT) supplementation during in vitro maturation (IVM) of human oocytes can reverse the age-related decline in oocyte quality.

Main methods

We enrolled 172 patients aged ≥35 years (older reproductive-aged women) and 83 patients aged <35 years (young women) who underwent in vitro fertilization between 2019 and 2022. We conducted IVM with and without 10 μM MT in immature oocytes of different ages. Oocyte fertilization and embryo development were observed using a stereomicroscope. We assessed the immunofluorescence intensity of mitochondrial function, measured the copy number of mitochondrial DNA (mtDNA), and examined the spindle and chromosome composition in in vitro mature stage II (IVM-MII) oocytes using immunofluorescence and second-generation sequencing.

Key findings

MT supplementation significantly improved the redox level in the IVM medium and IVM-MII oocytes in older reproductive-aged women. It also significantly increased the proportion of circular mtDNA and the adenosine triphosphate content in IVM-MII oocytes. In addition, the IVM-MII oocytes obtained with MT supplementation showed a significant improvement in the normal composition of the spindle and chromosomes. Thus, the aged immature oocytes also showed significantly improved maturation and blastocyst formation rates owing to the role of MT.

Significance

Supplementation with 10 μM MT in the IVM medium reverses the age-related decline in oocyte quality. Our findings provide a viable solution for enhancing fertility in older reproductive-aged women.

Effects of the neonatal intensive care environment on circadian health and development of preterm infants

The circadian system in mammals ensures adaptation to the light-dark cycle on Earth and imposes 24-h rhythmicity on metabolic, physiological and behavioral processes. The central circadian pacemaker is located in the brain and is entrained by environmental signals called Zeitgebers. From here, neural, humoral and systemic signals drive rhythms in peripheral clocks in nearly every mammalian tissue. During pregnancy, disruption of the complex interplay between the mother's rhythmic signals and the fetal developing circadian system can lead to long-term health consequences in the offspring. When an infant is born very preterm, it loses the temporal signals received from the mother prematurely and becomes totally dependent on 24/7 care in the Neonatal Intensive Care Unit (NICU), where day/night rhythmicity is usually blurred. In this literature review, we provide an overview of the fetal and neonatal development of the circadian system, and short-term consequences of disruption of this process as occurs in the NICU environment. Moreover, we provide a theoretical and molecular framework of how this disruption could lead to later-life disease. Finally, we discuss studies that aim to improve health outcomes after preterm birth by studying the effects of enhancing rhythmicity in light and noise exposure.

Melatonin as a Therapy for Preterm Brain Injury: What Is the Evidence?

Despite significant improvements in survival following preterm birth in recent years, the neurodevelopmental burden of prematurity, with its long-term cognitive and behavioral consequences, remains a significant challenge in neonatology. Neuroprotective treatment options to improve neurodevelopmental outcomes in preterm infants are therefore urgently needed. Alleviating inflammatory and oxidative stress (OS), melatonin might modify important triggers of preterm brain injury, a complex combination of destructive and developmental abnormalities termed encephalopathy of prematurity (EoP). Preliminary data also suggests that melatonin has a direct neurotrophic impact, emphasizing its therapeutic potential with a favorable safety profile in the preterm setting. The current review outlines the most important pathomechanisms underlying preterm brain injury and correlates them with melatonin's neuroprotective potential, while underlining significant pharmacokinetic/pharmacodynamic uncertainties that need to be addressed in future studies.

The role of Neurochemicals, Stress Hormones and Immune System in the Positive Feedback Loops between Diabetes, Obesity and Depression

Type 2 diabetes mellitus (T2DM) and depression are significant public health and socioeconomic issues. They commonly co-occur, with T2DM occurring in 11.3% of the US population, while depression has a prevalence of about 9%, with higher rates among youths. Approximately 31% of patients with T2DM suffer from depressive symptoms, with 11.4% having major depressive disorders, which is twice as high as the prevalence of depression in patients without T2DM. Additionally, over 80% of people with T2DM are overweight or obese. This review describes how T2DM and depression can enhance one another, using the same molecular pathways, by synergistically altering the brain's structure and function and reducing the reward obtained from eating. In this article, we reviewed the evidence that eating, especially high-caloric foods, stimulates the limbic system, initiating Reward Deficiency Syndrome. Analogous to other addictive behaviors, neurochemical changes in those with depression and/or T2DM are thought to cause individuals to increase their food intake to obtain the same reward leading to binge eating, weight gain and obesity. Treating the symptoms of T2DM, such as lowering HbA1c, without addressing the underlying pathways has little chance of eliminating the disease. Targeting the immune system, stress circuit, melatonin, and other alterations may be more effective.

Time Spent Outdoors and Associations with Sleep, Optimism, Happiness and Health before and during the COVID-19 Pandemic in Austria

Social restriction measures (SRM) implemented during the COVID-19 pandemic led to a reduction in time spent outdoors (TSO). The aim of this study was to describe TSO and evaluate its association with sleep outcomes, optimism, happiness and health-status before and during SRM. Two online surveys were conducted in 2017 (N = 1004) and 2020, during SRM (N = 1010), in samples representative of the age, sex and region of the Austrian population. Information on the duration of TSO, sleep, optimism, happiness and health-status was collected. Multivariable-adjusted logistic regression models were used to study the association of TSO with chronic insomnia, short sleep, late chronotype, optimism, happiness and self-rated health-status. The mean TSO was 3.6 h (SD: 2.18) in 2017 and 2.6 h (SD: 1.87) during times of SRM. Men and participants who were older, married or in a partnership and lived in a rural area reported longer TSO. Participants who spent less time outdoors were more likely to report short sleep or a late chronotype in both surveys and, in 2020, also chronic insomnia. Less TSO was associated with lower happiness and optimism levels and poor health-status. Our findings suggest that TSO may be a protective factor for sleep, mood and health, particularly during stressful and uncertain times.

Therapeutic Potential of Melatonin Counteracting Chemotherapy-Induced Toxicity in Breast Cancer Patients: A Systematic Review

The purpose of this systematic review is to provide an overview of the existing knowledge on the therapeutic potential of melatonin to counteract the undesirable effects of chemotherapy in breast cancer patients. To this aim, we summarized and critically reviewed preclinical- and clinical-related evidence according to the PRISMA guidelines. Additionally, we developed an extrapolation of melatonin doses in animal studies to the human equivalent doses (HEDs) for randomized clinical trials (RCTs) with breast cancer patients. For the revision, 341 primary records were screened, which were reduced to 8 selected RCTs that met the inclusion criteria. We assembled the evidence drawn from these studies by analyzing the remaining gaps and treatment efficacy and suggested future translational research and clinical trials. Overall, the selected RCTs allow us to conclude that melatonin combined with standard chemotherapy lines would derive, at least, a better quality of life for breast cancer patients. Moreover, regular doses of 20 mg/day seemed to increase partial response and 1-year survival rates. Accordingly, this systematic review leads us to draw attention to the need for more RCTs to provide a comprehensive view of the promising actions of melatonin in breast cancer and, given the safety profile of this molecule, adequate translational doses should be established in further RCTs.

Chronic obstructive pulmonary disease and emerging ER stress-related therapeutic targets

COPD pathogenesis is frequently associated with endoplasmic reticulum stress (ER stress) progression. Targeting the major unfolded protein response (UPR) branches in the ER stress pathway may provide pharmacotherapeutic selection strategies for treating COPD and enable relief from its symptoms. In this study, we aimed to systematically review the potential role of the ER stress inhibitors of major UPR branches (IRE1, PERK, and ATF6) in COPD-related studies and determine the current stage of knowledge in this field. The systematic review was carried out adhering to the PRISMA checklist based on published studies obtained from specific keyword searches of three databases, namely PubMed, ScienceDirect and Springer Database. The search was limited to the year 2000-2022 which includes all in vitro studies, in vivo studies and clinical trials related to the application of ER stress inhibitors toward COPD-induced models and disease. The risk of bias was evaluated using the QUIN, SYRCLE, revised Cochrane risk of bias tool for randomized trials (RoB 2.0) and NIH tool respectively. A total of 7828 articles were screened from three databases and a final total of 37 studies were included in the review. The ER stress and UPR pathways are potentially useful to prevent COPD progression and attenuate the exacerbation of COPD and related symptoms. Interestingly, the off-target effects from inhibition of the UPR pathway may be desirable or undesirable depending on context and therapeutic applications. Targeting the UPR pathway could have complex consequences as the production of ER molecules involved in folding may be impaired which could continuously provoke misfolding of proteins. Although several emerging compounds were noted to be potentially useful for targeted therapy against COPD, clinical studies have yet to be thoroughly explored.

Melatonin as mitochondria-targeted drug

Oxidative damage is associated to numerous diseases as well as aging development. Mitochondria found in most eukaryotic organisms to create the energy of the cell, generate free radicals during its action and they are chief targets of the oxidants. Mitochondrial activities outspread outside the borders of the cell and effect human physiology by modulating interactions among cells and tissues. Therefore, it has been implicated in several human disorders and conditions. Melatonin (MLT) is an endogenously created indole derivative that modifies several tasks, involving mitochondria-associated activities. These possessions make MLT a powerful defender against a selection of free radical-linked disorders. MLT lessens mitochondrial anomalies causing from extreme oxidative stress and may improve mitochondrial physiology. It is a potent and inducible antioxidant for mitochondria. MLT is produced in mitochondria of conceivably of all cells and it also appears to be a mitochondria directed antioxidant which has related defensive properties as the synthesized antioxidant molecules. This chapter summarizes the suggestion that MLT is produced in mitochondria as well as disorders of mitochondrial MLT production that may associate to a number of mitochondria-linked diseases. MLT as a mitochondria-targeted drug is also discussed.

Winery By-Products as Sources of Bioactive Tryptophan, Serotonin, and Melatonin: Contributions to the Antioxidant Power

The amino acid tryptophan and its derived molecules serotonin and melatonin are involved in a wide range of physiological functions that contribute significantly to human health, namely antioxidant, immune-active, and neurological properties. Grapes and wine are a source of these compounds, but their presence in wine by-products remains underexplored. Therefore, the aim of this work was the identification and quantification of tryptophan, serotonin, and melatonin in winery by-products (grape stems, grape pomace, and wine lees) by ultra-high performance liquid chromatography coupled to electrospray ionization and mass spectrometer with triple-quadrupole technology (UHPLC-ESI-QqQ-MS/MS), as well as the evaluation of the extracts obtained (by applying specific extraction conditions for each of them) for their antioxidant and reducing capacity (by three different and complementary methods: FRAP, ABTS^•+, and ORAC). Furthermore, correlation analyses were developed to establish the contribution of the different analytes to the total antioxidant activity. The main results obtained pointed out grape stems as the by-product with the highest tryptophan content (96.28 mg/kg dw) and antioxidant capacity (142.86, 166.72, and 363.24 mmol TE/kg dw, FRAP, ABTS^•+, and ORAC, respectively), while serotonin and melatonin were the predominant derivatives in grape pomace (0.086 and 0.902 µg/kg dw, respectively). The antioxidant capacity of the standards was also analysed at the concentrations found in the matrices studied. A significant correlation was found between the concentration of the pure tryptophan standard and the antioxidant capacity (ABTS^•+, r² = 0.891 at p < 0.001 (***); FRAP, r² = 0.885 at p < 0.01 (**); and ORAC, r² = 0.854 at p < 0.01 (**)). According to these results, winery by-products can be highlighted as valuable materials to be used as novel ingredients containing tryptophan, serotonin, and melatonin, while tryptophan was identified as the most relevant contributor (out of phenolic compounds) to the antioxidant capacity exhibited by wine by-products.

Traumatic Brain Injury, Sleep, and Melatonin-Intrinsic Changes with Therapeutic Potential

Traumatic brain injury (TBI) is one of the most prevalent causes of morbidity in the United States and is associated with numerous chronic sequelae long after the point of injury. One of the most common long-term complaints in patients with TBI is sleep dysfunction. It is reported that alterations in melatonin follow TBI and may be linked with various sleep and circadian disorders directly (via cellular signaling) or indirectly (via free radicals and inflammatory signaling). Work over the past two decades has contributed to our understanding of the role of melatonin as a sleep regulator and neuroprotective anti-inflammatory agent. Although there is increasing interest in the treatment of insomnia following TBI, a lack of standardization and rigor in melatonin research has left behind a trail of non-generalizable data and ambiguous treatment recommendations. This narrative review describes the underlying biochemical properties of melatonin as they are relevant to TBI. We also discuss potential benefits and a path forward regarding the therapeutic management of TBI with melatonin treatment, including its role as a neuroprotectant, a somnogen, and a modulator of the circadian rhythm.

Nitric oxide and hormesis

This present paper provides an assessment of the occurrence of nitric oxide (NO)-induced hormetic-biphasic dose/concentration relationships in biomedical research. A substantial reporting of such NO-induced hormetic effects was identified with particular focus on wound healing, tumor promotion, and sperm biology, including mechanistic assessment and potential for translational applications. Numerous other NO-induced hormetic effects have been reported, but require more development prior to translational applications. The extensive documentation of NO-induced biphasic responses, across numerous organs (e.g., bone, cardiovascular, immune, intestine, and neuronal) and cell types, suggests that NO-induced biological activities are substantially mediated via hormetic processes. These observations are particularly important because broad areas of NO biology are constrained by the quantitative features of the hormetic response. This determines the amplitude and width of the low dose stimulation, affecting numerous biomedical implications, study design features (e.g., number of doses, dose spacing, sample sizes, statistical power), and the potential success of clinical trials.

The effect of melatonin on sheep endometrial epithelial cell apoptosis through the receptor and non-receptor pathways

Melatonin potentially regulates the female animal reproductive function, but its regulatory mechanism in the apoptosis of sheep endometrial epithelial cells (SEECs) remains to be elucidated. In the present study, immunofluorescence staining, western blotting, and quantitative real-time polymerase chain reaction were performed to detect the distribution of melatonin receptors (MT1 and MT2) in the uterus of sheep and the effect of melatonin via the receptor and non-receptor pathways on the apoptosis of SEECs in vitro. The results showed that melatonin inhibits the apoptosis of SEECs to varying degrees to regulate the expression of estrogen receptors (ERs) and progesterone receptors (PGR) via its interaction with MT1 and MT2. In addition, the ER antagonist partially relieved the inhibitory effect of melatonin on the apoptosis of SEECs, while the PGR antagonist did not. Thus, melatonin mediates endometrial epithelial apoptosis through the MT receptors and also by regulating estrogen function. This study provides evidence of the regulatory mechanism of melatonin on the physiological function of the sheep uterus.

Melatonin and Health: Insights of Melatonin Action, Biological Functions, and Associated Disorders

Melatonin is ubiquitous molecule with wide distribution in nature and is produced by many living organisms. In human beings, pineal gland is the major site for melatonin production and to lesser extent by retina, lymphocytes, bone marrow, gastrointestinal tract, and thymus. Melatonin as a neurohormone is released into circulation wherein it penetrates all tissues of the body. Melatonin synthesis and secretion is supressed by light and enhanced by dark. Melatonin mostly exerts its effect through different pathways with melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2) being the predominant type of receptor that are mainly expressed by many mammalian organs. Melatonin helps to regulate sleep patterns and circadian rhythms. In addition, melatonin acts as an antioxidant and scavenges excessive free radicals generated in the body by anti-excitatory and anti-inflammatory properties. A multiple array of other functions are displayed by melatonin that include oncostatic, hypnotic, immune regulation, reproduction, puberty timing, mood disorders, and transplantation. Deficiencies in the production or synthesis of melatonin have been found to be associated with onset of many disorders like breast cancer and neurodegenerative disorders. Melatonin could be used as potential analgesic drug in diseases associated with pain and it has quite promising role there. In the past century, a growing interest has been developed regarding the wide use of melatonin in treating various diseases like inflammatory, gastrointestinal, cancer, mood disorders, and others. Several melatonin agonists have been synthesized and are widely used in disease treatment. In this review, an effort has been made to describe the biochemistry of melatonin along with its therapeutic potential in various diseases of humans.

Melatonin as Modulator for Sulfur and Nitrogen Mustard-Induced Inflammation, Oxidative Stress and DNA Damage: Molecular Therapeutics

Sulfur and nitrogen mustards, bis(2-chloroethyl)sulfide and tertiary bis(2-chloroethyl) amines, respectively, are vesicant warfare agents with alkylating activity. Moreover, oxidative/nitrosative stress, inflammatory response induction, metalloproteinases activation, DNA damage or calcium disruption are some of the toxicological mechanisms of sulfur and nitrogen mustard-induced injury that affects the cell integrity and function. In this review, we not only propose melatonin as a therapeutic option in order to counteract and modulate several pathways involved in physiopathological mechanisms activated after exposure to mustards, but also for the first time, we predict whether metabolites of melatonin, cyclic-3-hydroxymelatonin, N1-acetyl-N2-formyl-5-methoxykynuramine, and N1-acetyl-5-methoxykynuramine could be capable of exerting a scavenger action and neutralize the toxic damage induced by these blister agents. NLRP3 inflammasome is activated in response to a wide variety of infectious stimuli or cellular stressors, however, although the precise mechanisms leading to activation are not known, mustards are postulated as activators. In this regard, melatonin, through its anti-inflammatory action and NLRP3 inflammasome modulation could exert a protective effect in the pathophysiology and management of sulfur and nitrogen mustard-induced injury. The ability of melatonin to attenuate sulfur and nitrogen mustard-induced toxicity and its high safety profile make melatonin a suitable molecule to be a part of medical countermeasures against blister agents poisoning in the near future.