Melatonin in Heart Failure: A Promising Therapeutic Strategy?

The chronobiology of human heart failure: clinical implications and therapeutic opportunities

Circadian variation in cardiovascular and metabolic dynamics arises from interactions between intrinsic rhythms and extrinsic cues. By anticipating and accommodating adaptation to awakening and activity, their synthesis maintains homeostasis and maximizes efficiency, flexibility, and resilience. The dyssynchrony of cardiovascular load and energetic capacity arising from attenuation or loss of such rhythms is strongly associated with incident heart failure (HF). Once established, molecular, neurohormonal, and metabolic rhythms are frequently misaligned with each other and with extrinsic cycles, contributing to HF progression and adverse outcomes. Realignment of biological rhythms via lifestyle interventions, chronotherapy, and time-tailored autonomic modulation represents an appealing potential strategy for improving HF-related morbidity and mortality.

Unlocking the health benefits of melatonin supplementation: A promising preventative and therapeutic strategy

Melatonin (MLT) is crucial in controlling human sleep-wake patterns. While it has long been recognized for regulating circadian rhythms, its demonstrated efficacy in managing various diseases has recently gained considerable attention. This review discusses MLT's potential preventative and therapeutic effects on various diseases. Several studies have focused on examining the molecular mechanisms through which MLT brings about its protective or therapeutic effects on various diseases, including cancer, obesity, coronavirus, and cardiovascular diseases. Numerous preventative and therapeutic applications of MLT have been proposed, resulting from its ability to function as an antioxidant, anti-cancer, anti-inflammatory, and immune-regulating agent. There is a need for further research to determine MLT's long-term effects on antioxidant defense systems, its preventative and therapeutic benefits, and its molecular basis.

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

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

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.

Revealing Melatonin's Mysteries: Receptors, Signaling Pathways, and Therapeutics Applications

Melatonin (5-methoxy-acetyl tryptamine) is a sleep-inducing hormone, and the pineal gland produces it in response to the circadian clock of darkness. In the body, MT1 and MT2 receptors are mostly found, having an orthosteric pocket and ligand binding determinants. Melatonin acts by binding on melatonin receptors, intracellular proteins, and orphan nuclear receptors. It inhibits adenyl cyclase and activates phospholipase C, resulting in gene expression and an intracellular alteration environment. Melatonin signaling pathways are also associated with other intracellular signaling pathways, i. e., cAMP/PKA and MAPK/ERK pathways. Relative expression of different proteins depends on the coupling profile of G protein, accounting pharmacology of the melatonin receptor bias system, and mediates action in a Gi-dependent manner. It shows antioxidant, antitumor, antiproliferative, and neuroprotective activity. Different types of melatonin agonists have been synthesized for the treatment of sleeping disorders. Researchers have developed therapeutics that target melatonin signaling, which could benefit a wide range of medical conditions. This review focuses on melatonin receptors, pharmacology, and signaling cascades; it aims to provide basic mechanical aspects of the receptor's pharmacology, melatonin's functions in cancer and neurodegenerative diseases, and any treatments and drugs designed for these diseases. This will allow a basic comparison between the receptors in question, highlighting any parallels and differences that may exist and providing fundamental knowledge about these receptors to future researchers.

New Perspectives on the Role and Therapeutic Potential of Melatonin in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. It is essential to develop novel interventions to prevent/delay CVDs by targeting their fundamental cellular and molecular processes. Melatonin is a small indole molecule acting both as a hormone of the pineal gland and as a local regulator molecule in various tissues. It has multiple features that may contribute to its cardiovascular protection. Moreover, melatonin enters all cells and subcellular compartments and crosses morphophysiological barriers. Additionally, this indoleamine also serves as a safe exogenous therapeutic agent. Increasing evidence has demonstrated the beneficial effects of melatonin in preventing and improving cardiovascular risk factors. Exogenous administration of melatonin, as a result of its antioxidant and anti-inflammatory properties, has been reported to decrease blood pressure, protect against atherosclerosis, attenuate molecular and cellular damage resulting from cardiac ischemia/reperfusion, and improve the prognosis of myocardial infarction and heart failure. This review aims to summarize the beneficial effects of melatonin against these conditions, the possible protective mechanisms of melatonin, and its potential clinical applicability in CVDs.

Melatonin inhibits atrazine-induced mitochondrial impairment in cerebellum of mice: Modulation of cGAS-STING-NLRP3 axis-dependent cell pyroptosis

The global prevalence of Neurological disorders has increased alarmingly in response to environmental and lifestyle changes. Atrazine (ATZ) is a difficult to degrade soil and water pollutant with well-known neurotoxicity. Melatonin (MT), an antioxidant with chemoprotective properties, has a potential therapeutic effect on cerebellar damage caused by ATZ exposure. The aim of this study was to explore the effects and underlying mechanisms of MT on the cerebellar inflammatory response and pyroptosis induced by ATZ exposure. In this study, C57BL/6J mice were treated with ATZ (170 mg/kg BW/day) and MT (5 mg/kg BW/day) for 28 days. Our results revealed that MT alleviated the histopathological changes, ultrastructural damage, oxidative stress and decrease of mitochondrial membrane potential (ΔΨm) in the cerebellum induced by ATZ exposure. ATZ exposure damaged the mitochondria leading to release of mitochondrial DNA (mtDNA) to the cytoplasm, MT activated the cyclic GMP-AMP synthetase interferon gene stimulator (cGAS-STING) axis to alleviate inflammation and pyroptosis caused by ATZ exposure. In general, our study provided new evidence that the cGAS-STING-NLRP3 axis plays an important role in the treatment of ATZ-induced cerebellar injury by MT.

Therapeutic potential of melatonin in targeting molecular pathways of organ fibrosis

Fibrosis, the excessive deposition of fibrous connective tissue in an organ in response to injury, is a pathological condition affecting many individuals worldwide. Fibrosis causes the failure of tissue function and is largely irreversible as the disease progresses. Pharmacologic treatment options for organ fibrosis are limited, but studies suggest that antioxidants, particularly melatonin, can aid in preventing and controlling fibrotic damage to the organs. Melatonin, an indole nocturnally released from the pineal gland, is commonly used to regulate circadian and seasonal biological rhythms and is indicated for treating sleep disorders. While it is often effective in treating sleep disorders, melatonin's anti-inflammatory and antioxidant properties also make it a promising molecule for treating other disorders such as organ fibrosis. Melatonin ameliorates the necrotic and apoptotic changes that lead to fibrosis in various organs including the heart, liver, lung, and kidney. Moreover, melatonin reduces the infiltration of inflammatory cells during fibrosis development. This article outlines the protective effects of melatonin against fibrosis, including its safety and potential therapeutic effects. The goal of this article is to provide a summary of data accumulated to date and to encourage further experimentation with melatonin and increase its use as an anti-fibrotic agent in clinical settings.

Cardiometabolic Changes in Sirtuin1-Heterozygous Mice on High-Fat Diet and Melatonin Supplementation

A hypercaloric fatty diet predisposes an individual to metabolic syndrome and cardiovascular complications. Sirtuin1 (SIRT1) belongs to the class III histone deacetylase family and sustains anabolism, mitochondrial biogenesis, and fat distribution. Epididymal white adipose tissue (eWAT) is involved in inflammation, whilst interscapular brown adipose tissue (iBAT) drives metabolism in obese rodents. Melatonin, a pineal indoleamine, acting as a SIRT1 modulator, may alleviate cardiometabolic damage. In the present study, we morphologically characterized the heart, eWAT, and iBAT in male heterozygous SIRT1+/- mice (HET mice) on a high-fat diet (60%E lard) versus a standard rodent diet (8.5% E fat) and drinking melatonin (10 mg/kg) for 16 weeks. Wild-type (WT) male C57Bl6/J mice were similarly fed for comparison. Cardiomyocyte fibrosis and endoplasmic reticulum (ER) stress response worsened in HET mice on a high-fat diet vs. other groups. Lipid peroxidation, ER, and mitochondrial stress were assessed by 4 hydroxy-2-nonenal (4HNE), glucose-regulated protein78 (GRP78), CCAA/enhancer-binding protein homologous protein (CHOP), heat shock protein 60 (HSP60), and mitofusin2 immunostainings. Ultrastructural analysis indicated the prevalence of atypical inter-myofibrillar mitochondria with short, misaligned cristae in HET mice on a lard diet despite melatonin supplementation. Abnormal eWAT adipocytes, crown-like inflammatory structures, tumor necrosis factor alpha (TNFα), and iBAT whitening characterized HET mice on a hypercaloric fatty diet and were maintained after melatonin supply. All these data suggest that melatonin's mechanism of action is strictly linked to full SIRT1 expression, which is required for the exhibition of effective antioxidant and anti-inflammatory properties.

Melatonin as a therapeutic agent for alleviating endothelial dysfunction in cardiovascular diseases: Emphasis on oxidative stress

The vascular endothelium is vital in maintaining cardiovascular health by regulating vascular permeability and tone, preventing thrombosis, and controlling vascular inflammation. However, when oxidative stress triggers endothelial dysfunction, it can lead to chronic cardiovascular diseases (CVDs). This happens due to oxidative stress-induced mitochondrial dysfunction, inflammatory responses, and reduced levels of nitric oxide. These factors cause damage to endothelial cells, leading to the acceleration of CVD progression. Melatonin, a natural antioxidant, has been shown to inhibit oxidative stress and stabilize endothelial function, providing cardiovascular protection. The clinical application of melatonin in the prevention and treatment of CVDs has received widespread attention. In this review, based on bibliometric studies, we first discussed the relationship between oxidative stress-induced endothelial dysfunction and CVDs, then summarized the role of melatonin in the treatment of atherosclerosis, hypertension, myocardial ischemia-reperfusion injury, and other CVDs. Finally, the potential clinical use of melatonin in the treatment of these diseases is discussed.

Examination of correlations between vitamin D and melatonin levels with sleep among women aged 18-49 years

OBJECTIVES

Although clinical research is still going on to determine any relationship between vitamin D and sleep regulation, only few studies have identified the role of vitamin D metabolism in sleep disorders. The current study aims to examine the incidence of vitamin D deficiency/insufficiency in the sample group and its effects on sleep quality and melatonin level.

METHODS

A cross-sectional study was designed. A total of 79 women aged 18-49 years who applied to the research and training hospital between 1 October and 30 November 2021 participated in the study. Data were collected using a socio-demographic questionnaire prepared by the authors and the Pittsburgh Sleep Quality Index (PSQI). Blood samples were taken from the participants, also, 25-OH-vitamin D3 and melatonin levels in serum samples were measured by ELISA.

RESULTS

The participants (n = 79) were aged 29.61 ± 11.14 years. The mean total PSQI scores of the participants were calculated as 5.77 ± 2.70. We determined that 64.6% of the participants had vitamin D deficiency, 21.5% had vitamin D insufficiency, and 13.9% of the participants were vitamin D sufficient. The mean melatonin level was found to be 24.77 ± 27.77 ng/L. We determined that an increase in the melatonin levels decreases the risk of vitamin D deficiency. Besides, our findings showed a good positive correlation between serum melatonin and 25 OH vitamin D3 levels (r = 0.544, p < 0.001).

CONCLUSION

Our results indicate that the correction of vitamin D insufficiency can positively affect melatonin levels, therefore, it may positively contribute to the treatment of sleep disorders related to melatonin deficiency.

The Therapeutic Strategies Targeting Mitochondrial Metabolism in Cardiovascular Disease

Cardiovascular disease (CVD) is a group of systemic disorders threatening human health with complex pathogenesis, among which mitochondrial energy metabolism reprogramming has a critical role. Mitochondria are cell organelles that fuel the energy essential for biochemical reactions and maintain normal physiological functions of the body. Mitochondrial metabolic disorders are extensively involved in the progression of CVD, especially for energy-demanding organs such as the heart. Therefore, elucidating the role of mitochondrial metabolism in the progression of CVD is of great significance to further understand the pathogenesis of CVD and explore preventive and therapeutic methods. In this review, we discuss the major factors of mitochondrial metabolism and their potential roles in the prevention and treatment of CVD. The current application of mitochondria-targeted therapeutic agents in the treatment of CVD and advances in mitochondria-targeted gene therapy technologies are also overviewed.

Melatonin Attenuates Extracellular Matrix Accumulation and Cardiac Injury Manifested by Copper

Copper-induced cardiac injury is not widely reported in spite of its ability to cause oxidative damage and tissue injury. Structural and morphological changes in the cardiac tissue are triggered via oxidative stress and inflammatory responses following copper exposure. The varied and unavoidable exposure of copper through contaminated food and water warrants a safe and effective agent against its harmful effects. Since the heart is highly sensitive to changes in the redox balance, the present study was undertaken to examine the protective effects of melatonin against copper-induced cardiac injury. Sprague Dawley (SD) rats were exposed to 100 ppm of elemental copper via drinking water for 4 months. The cardiac tissue was evaluated for various biochemical, histological, and protein expression studies. Animals exposed to copper exhibited induced oxidative stress and cardiac injury compared to normal control. To this end, we found that melatonin treatment ameliorated copper-induced alterations in tissue oxidative variables like ROS, nitrate, MDA, and GSH. In addition, histological examinations unravelled decreased cardiac muscle dilation, atrophy, and cardiomyopathy in melatonin-treated rats. Furthermore, melatonin-treated rats were associated with reduced tissue copper levels, collagen deposition, α-SMA, and increased HO-1 expression as compared to rats exposed exclusively to copper. Moreover, the levels of NF-κB and cardiac markers such as CK-MB, cTnI, and cTnT were found to be decreased in the melatonin-treated animals. Altogether, melatonin-triggered increase in antioxidant capacity resulting in reduced aggregation of ECM components demonstrates the therapeutic potential of melatonin in the treatment of cardiac injury and tissue fibrosis.

Redox Biology of Melatonin: Discriminating Between Circadian and Noncircadian Functions

Melatonin has not only to be seen as a regulator of circadian clocks. In addition to its chronobiotic functions, it displays other actions, especially in cell protection. This includes antioxidant, anti-inflammatory, and mitochondria-protecting effects. Although protection is also modulated by the circadian system, the respective actions of melatonin can be distinguished and differ with regard to dose requirements in therapeutic settings. It is the aim of this article to outline these differences in terms of function, signaling, and dosage. Focus has been placed on both the nexus and the dissecting properties between circadian and noncircadian mechanisms. This has to consider details beyond the classic view of melatonin's role, such as widespread synthesis in extrapineal tissues, formation in mitochondria, effects on the mitochondrial permeability transition pore, and secondary signaling, for example, via upregulation of sirtuins and by regulating noncoding RNAs, especially microRNAs. The relevance of these findings, the differences and connections between circadian and noncircadian functions of melatonin shed light on the regulation of inflammation, including macrophage/microglia polarization, damage-associated molecular patterns, avoidance of cytokine storms, and mitochondrial functions, with numerous consequences to antioxidative protection, that is, aspects of high actuality with regard to deadly viral and bacterial diseases. Antioxid. Redox Signal. 37, 704-725.

Is Melatonin the "Next Vitamin D"?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements

Melatonin has become a popular dietary supplement, most known as a chronobiotic, and for establishing healthy sleep. Research over the last decade into cancer, Alzheimer's disease, multiple sclerosis, fertility, PCOS, and many other conditions, combined with the COVID-19 pandemic, has led to greater awareness of melatonin because of its ability to act as a potent antioxidant, immune-active agent, and mitochondrial regulator. There are distinct similarities between melatonin and vitamin D in the depth and breadth of their impact on health. Both act as hormones, affect multiple systems through their immune-modulating, anti-inflammatory functions, are found in the skin, and are responsive to sunlight and darkness. In fact, there may be similarities between the widespread concern about vitamin D deficiency as a "sunlight deficiency" and reduced melatonin secretion as a result of "darkness deficiency" from overexposure to artificial blue light. The trend toward greater use of melatonin supplements has resulted in concern about its safety, especially higher doses, long-term use, and application in certain populations (e.g., children). This review aims to evaluate the recent data on melatonin's mechanisms, its clinical uses beyond sleep, safety concerns, and a thorough summary of therapeutic considerations concerning dietary supplementation, including the different formats available (animal, synthetic, and phytomelatonin), dosing, timing, contraindications, and nutrient combinations.

Protective Effects and Mechanisms of Melatonin on Stress Myocardial Injury in Rats

ABSTRACT

Prolonged and intense stress can exceed the body's normal self-regulation and limited compensatory and repair capacity, resulting in pathological damage to the body. In this study, we established a rat stress myocardial injury (SMI) model to explore the protective effect of melatonin (MLT) on SMI and its possible mechanisms of action. Adult female Sprague Dawley (SD) rats were randomly divided into 5 groups: blank control group (NC), SMI group, MLT low-dose group, MLT medium-dose group, and MLT high-dose group, and 10 rats in each group were used to establish a SMI model by the water immersion restraint method. We observed the changes in body weight and tail vein glucose of each group. Serum levels of corticosterone (Cort), creatine kinase isoenzyme (CK-MB), and Troponin Ⅰ (Tn-Ⅰ) and activity of lactic acid dehydrogenase were measured by ELISA. Transcriptome sequencing was used to find differentially expressed genes in the control and model groups, and the results were verified by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR). HE staining was used to visualize the pathological changes in the heart tissue of each group, and Western blot was used to study the differences in protein expression in the cardiomyocytes of each group to further corroborate the results. The body weight growth rate of rats in the SMI group was significantly lower than that of the NC group ( P < 0.01), and the body weight growth rate of rats in the MLT high-dose group was significantly higher than that of the SMI group ( P < 0.05) with no significant difference compared with the NC group rats. The mean blood glucose of rats in the SMI group was significantly higher compared with the NC group ( P < 0.001), while the mean blood glucose of rats in the MLT administration groups was dose-dependently reduced compared with the SMI group. By RNA-seq and bioinformatics tools such as KEGG and Gene ontology, we found that the circadian clock-related genes Ciart , Arnt1 , Per1 , and Dbp were significantly downregulated in the SMI group during water immersion stress, and differentially expressed genes were enriched in the p38MAPK signaling pathway and p53 signaling pathway. Moreover, genes related to inflammation and apoptosis were differentially expressed. ELISA results showed that Cort, CK-MB, and Tn-Ⅰ levels were significantly higher in the SMI group compared with the NC group ( P < 0.01) and melatonin reduced the levels of Cort, CK-MB, and Tn-Ⅰ and decreased lactic acid dehydrogenase activity in rat serum. HE staining results showed that melatonin could attenuate stress-generated myocardial injury. Western blot showed that melatonin reduced the expression of p38MAPK, p53, Bax, and caspase-3 and increased the expression of Bcl-2 protein in rat heart. Melatonin can inhibit myocardial injury caused by water immersion, and its mechanism of action may be related to the regulation of the expression of circadian clock genes such as Ciart , Arnt1 , Per1 , and Dbp ; the inhibition of the expression of proapoptotic proteins such as p38MAPK, p53, Bax, and caspase-3; and the increase of the expression of Bcl-2 antiapoptotic protein.

Evidence for the Benefits of Melatonin in Cardiovascular Disease

The pineal gland is a neuroendocrine gland which produces melatonin, a neuroendocrine hormone with critical physiological roles in the circadian rhythm and sleep-wake cycle. Melatonin has been shown to possess anti-oxidant activity and neuroprotective properties. Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.

Melatonin inhibits angiotensin II-induced atrial fibrillation through preventing degradation of Ang II Type I Receptor-Associated Protein (ATRAP)

Angiotensin II (Ang II) induced Atrial fibrillation (AF) often accompanied with reduced ATRAP which is a negative modulator of Ang II type 1 receptor (AT1R). Melatonin can protect against AF, but the underlying molecular mechanism remains poorly understood. In this study, Ang II was used to induce AF, and AF inducibility and duration were documented telemetrically. Ang II-infused mice had a higher AF incidence, which was associated with atrial fibrosis, inflammation, and oxidative stress. Melatonin partially inhibited these effects, and enforced expression of siRNA-ATRAP in atria counteracted the beneficial role of melatonin. Specifically, melatonin inhibited expression of Ang II-induced proteasome and immunoproteasome subunits β2, β2i, β5, and β5i as well as their corresponding trypsin-like and chymotrypsin-like activities and blocked ATRAP degradation. In turn, this inhibited AT1R-mediated NF-κB signaling, transforming growth factor (TGF)-β1/Smad signaling in the atria, and thereby affected atrial remodeling and AF. Melatonin receptor inhibition by the chemical inhibitor luzindole partially inhibited the inhibitory effects of melatonin on proteasome activity and also Ang II-induced pathological changes in the atria. Overall, our study demonstrates that melatonin protects against Ang II-induced AF by inhibiting proteasome activity and stabilizing ATRAP expression, and these effects are partially dependent on melatonin receptor activation.

Protective effects of melatonin in cisplatin-induced cardiac toxicity: possible role of BDNF-TNF-α signaling pathway

Purpose:

The present study explored the role of melatonin in cisplatin-induced cardiac injury along with the possible role of brain-derived neurotrophic factor (BDNF) in melatonin-mediated effects.

Methods:

Wistar rats were administered cisplatin (10 mg/kg), and cardiac injury was assessed by measuring the levels of cardiac troponin (cTnT) and lactate dehydrogenase (LDH-1).The extent of apoptosis was measured by measuring caspase-3 (pro-apoptotic) and Bcl-2 (anti-apoptotic) in hearts. The levels of BDNF, tumour necrosis factor α (TNF-α) and reduced glutathione were measured in heart. Melatonin (5 and 10 mg/kg) was administered for 15 days, and the role of BDNF was identified by co-administering BDNF inhibitor, ANA-12 (0.25 and 0.5 mg/kg).

Results:

Melatonin attenuated cTnT and LDH-1 levels along with reduction in caspase-3 and increase in Bcl-2. It also increased cisplatin-induced decrease in BDNF, increase in TNF-α and decrease in reduced glutathione levels. Moreover, ANA-12 abolished the cardioprotective effects, anti-inflammatory and antioxidant effects of melatonin suggesting the role of BDNF in melatonin-mediated effects in cisplatin-induced cardiac injury.

Conclusions:

Melatonin is useful in cisplatin-induced cardiac injury, which may be due to an increase in BDNF, decrease in inflammation and increase in antioxidant activities.

Melatonin supplementation improves N-terminal pro-B-type natriuretic peptide levels and quality of life in patients with heart failure with reduced ejection fraction: Results from MeHR trial, a randomized clinical trial

BACKGROUND

Melatonin, the major secretion of the pineal gland, has beneficial effects on the cardiovascular system and might advantage heart failure with reduced ejection fraction (HFrEF) by attenuating the effects of the renin-angiotensin-aldosterone and sympathetic system on the heart besides its antioxidant and anti-inflammatory effects.

HYPOTHESIS

We hypothesized that oral melatonin might improve echocardiographic parameters, serum biomarkers, and a composite clinical outcome (including quality of life, hospitalization, and mortality) in patients with HFrEF.

METHODS

A placebo-controlled double-blinded randomized clinical trial was conducted on patients with stable HFrEF. The intervention was 10 mg melatonin or placebo tablets administered every night for 24 weeks. Echocardiography and measurements of N-terminal pro-B-type natriuretic peptide (NT-Pro BNP), high-sensitivity C-reactive protein, lipid profile, and psychological parameters were done at baseline and after 24 weeks.

RESULTS

Overall, 92 patients were recruited, and 85 completed the study (melatonin: 42, placebo: 43). Serum NT-Pro BNP decreased significantly in the melatonin compared with the placebo group (estimated marginal means for difference [95% confidence interval]: 111.0 [6.2-215.7], p = .044). Moreover, the melatonin group had a significantly better clinical outcome (0.93 [0.18-1.69], p = .017), quality of life (5.8 [0.9-12.5], p = .037), and New York Heart Association class (odds ratio: 12.9 [1.6-102.4]; p = .015) at the end of the trial. Other studied outcomes were not significantly different between groups.

CONCLUSIONS

Oral melatonin decreased NT-Pro BNP and improved the quality of life in patients with HFrEF. Thus it might be a beneficial supplement in HFrEF.

Short-term melatonin supplementation decreases oxidative stress but does not affect left ventricular structure and function in myxomatous mitral valve degenerative dogs

Background

Cardiac wall stress and high oxidative stress are often found in cases of myxomatous mitral valve degenerative (MMVD) disease and can lead to myocardial injuries and cardiac dysfunction. Melatonin, an antioxidant, has been shown to exert cardioprotection in laboratory animal models. However, its effect on metabolic parameters and left ventricular (LV) adaptation in MMVD dogs has rarely been investigated. This clinical trial hypothesized that a melatonin supplement for 4 weeks would improve metabolic parameters, LV structure (diameters and wall thickness), and LV function in MMVD dogs. Blood profiles, echocardiograms, and oxidative stress levels were obtained from 18 dogs with MMVD stage B2 and C at baseline and after prescribed Melatonin (2 mg/kg) for 4 weeks. Eleven dogs with MMVD stage B2 and C, which received a placebo, were evaluated as a control group.

Results

In this clinical trial, the baseline plasma malondialdehyde (MDA) was no different between the treatment and placebo groups. The post-treatment plasma MDA levels (4.50 ± 0.63 mg/mL) in the treatment group was significantly decreased after 4 weeks of melatonin supplementation compared to pre-treatment levels (7.51 ± 1.11 mg/mL) (P = 0.038). However, blood profiles and LV structure and function investigated using echocardiography were found not to different between pre-and post-treatment in each group. No adverse effects were observed following melatonin supplementation.

Conclusions

This clinical trial demonstrated that a melatonin supplement for 4 weeks can attenuate oxidative stress levels in MMVD dogs, especially in MMVD stage C, but does not result in LV structural changes or LV function in MMVD dogs of either stage B2 or stage C.

The Effects of Melatonin on the Oxidative Stress and Duration of Atrial Fibrillation after Coronary Artery Bypass Graft Surgery: A Randomized Controlled Trial

BACKGROUND

Atrial Fibrillation (AF) is a common complication following Coronary artery bypass graft (CABG) Surgery, which may be due to oxidative stress, necrosis and inflammation during CABG and can lead to increases the length of hospital stay and the risk of morbidity and mortality. Melatonin is a hormone with anti-oxidant and anti-inflammatory properties in the cardiovascular system. This study assessed the efficacy of sublingual consumption of melatonin in reducing necrosis and inflammation, in patients undergoing CABG with respect to C-reactive protein (hs-CRP), Creatine Kinase-Muscle-Brain subunits (CK-MB) and cardiac Troponin T (cTnT) levels.

METHODS

One hundred and two patients were enrolled and twenty-six patients were excluded during the study process and finally seventy-six patients undergoing CABG surgery randomly assigned to melatonin group (n = 38, 12 mg sublingual melatonin the evening before and 1 hour before surgery, or the control group which did not receive Melatonin, n = 38). Three patients in the melatonin group and three patients in the control group were excluded from the study because of discontinued intervention and lost to follow up. The samples were collected before and 24 hours after surgery. hs-CRP, CK-MB, and cTnT levels were measured in all patients with the Elisa method.

RESULTS

There was no significant difference in influencing variables among the groups at the baseline. The incidence of AF following CABG surgery was not statistically significant between the two groups, (p-value = 0.71). However, the duration of AF (p-value = 0.01), the levels of hs-CRP (p-value = 0.001) and CK-MB (p-value = 0.004) measured, 24 hours after surgery were significantly lower in the melatonin group. cTnT levels measured 24 hours post-CABG did not show any significant difference in both groups (p-value = 0.52).

CONCLUSION

Our findings suggest that the administration of melatonin may help modulate oxidative stress, based on the reduction of the levels of hs-CRP, CK-MB, and the duration of AF following CABG surgery.

Melatonin and prolonged physical activity attenuated the detrimental effects of diabetic condition on murine cardiac tissue

In this study, the combined effects of four-week swimming training and melatonin were examined on the oxidative response, inflammation, apoptosis, and angiogenesis capacity of cardiac tissue in the mouse model of diabetes. The mice were randomly allocated into five groups (n = 10 per group) as follows: Control; Diabetic group; Diabetic + Melatonin group; Diabetic + Exercise group; and Diabetic + Exercise + Melatonin group. 50 mg/kg streptozotocin was intraperitoneally administrated. In melatonin-treated groups, melatonin was injected intraperitoneally at 3 mg/kg body weight for four weeks and twice weekly. Swimming exercises were performed for four weeks. We measured cardiac superoxide dismutase, glutathione peroxidase enzymes, malondialdehyde, and total antioxidant capacity. The expression of tumor necrosis factor-α, Caspase‑3, Sirtuin1, and Connexin-43 was measured using real-time PCR analysis. The vascular density was analyzed by immunohistochemistry using CD31 and α-smooth muscle actin antibodies. The combination of melatonin and exercise elevated cardiac superoxide dismutase, glutathione peroxidase coincided with the reduction of malondialdehyde and increase of total antioxidant capacity as compared to the diabetic mice (p < 0.05). In Diabetic + Exercise + Melatonin mice, tumor necrosis factor-α, Caspase‑3 was significantly down-regulated compared to the Diabetic group (p < 0.05). Melatonin and exercise suppressed the expression of Connexin-43 and Sirtuin1 in diabetic mice in comparison with the control mice (p < 0.05). H & E staining showed necrosis and focal hyperemia reduction in the Diabetic + Exercise + Melatonin group compared to the Diabetic group. Data showed a decrease of CD31+ and α-smooth muscle actin+ vessels in the Diabetic group as compared to the normal samples (p < 0.05). The number of CD31+ vessels, but not α-smooth muscle actin+ type, increased in the Diabetic + Exercise + Melatonin group compared to the Diabetic mice. These data demonstrated that exercise along with melatonin administration could diminish the detrimental effects of diabetes on cardiac tissue via using different mechanisms.

Melatonin to Rescue the Aged Heart: Antiarrhythmic and Antioxidant Benefits

Aging comes with gradual loss of functions that increase the vulnerability to disease, senescence, and death. The mechanisms underlying these processes are linked to a prolonged imbalance between damage and repair. Damaging mechanisms include oxidative stress, mitochondrial dysfunction, chronodisruption, inflammation, and telomere attrition, as well as genetic and epigenetic alterations. Several endogenous tissue repairing mechanisms also decrease. These alterations associated with aging affect the entire organism. The most devastating manifestations involve the cardiovascular system and may lead to lethal cardiac arrhythmias. Together with structural remodeling, electrophysiological and intercellular communication alterations during aging predispose to arrhythmic events. Despite the knowledge on repairing mechanisms in the cardiovascular system, effective antiaging strategies able to reduce the risk of arrhythmias are still missing. Melatonin is a promising therapeutic candidate due to its pleiotropic actions. This indoleamine regulates chronobiology and endocrine physiology. Of relevance, melatonin is an antiaging, antioxidant, antiapoptotic, antiarrhythmic, immunomodulatory, and antiproliferative molecule. This review focuses on the protective effects of melatonin on age-induced cardiac functional and structural alterations, potentially becoming a new fountain of youth for the heart.

Melatonin and healthy aging

Preservation of a robust circadian rhythmicity (particulsarly of the sleep/wake cycle), a proper nutrition and adequate physical exercise are key elements for healthy aging. Aging comes along with circadian alteration, e.g. a disrupted sleep and inflammation, that leads to metabolic disorders. In turn, sleep cycle disturbances cause numerous pathophysiological changes that accelerates the aging process. In the central nervous system, sleep disruption impairs several functions, among them, the clearance of waste molecules. The decrease of plasma melatonin, a molecule of unusual phylogenetic conservation present in all known aerobic organisms, plays a particular role as far as the endocrine sequels of aging. Every day, the late afternoon/nocturnal increase of melatonin synchronizes both the central circadian pacemaker located in the hypothalamic suprachiasmatic nuclei as well as myriads of peripheral cellular circadian clocks. This is called the "chronobiotic effect" of melatonin, the methoxyindole being the prototype of the endogenous family of chronobiotic agents. In addition, melatonin exerts a significant cytoprotective action by buffering free radicals and reversing inflammation via down regulation of proinflammatory cytokines, suppression of low degree inflammation and prevention of insulin resistance. Because of these properties melatonin has been advocated to be a potential therapeutic tool in COVID 19 pandemic. Melatonin administration to aged animals counteracts a significant number of senescence-related changes. In humans, melatonin is effective both as a chronobiotic and a cytoprotective agent to maintain a healthy aging. Circulating melatonin levels are consistently reduced in the metabolic syndrome, ischemic and non-ischemic cardiovascular diseases and neurodegenerative disorders like the Alzheimer's and Parkinson's diseases. The potential therapeutic value of melatonin has been suggested by a limited number of clinical trials generally employing melatonin in the 2-10mg/day range. However, from animal studies the cytoprotective effects of melatonin need higher doses to become apparent (i.e. in the 100mg/day range). Hence, controlled studies employing melatonin doses in this range are urgently needed.

Potential Role of Melatonin as an Adjuvant for Atherosclerotic Carotid Arterial Stenosis

Carotid artery stenosis (CAS) is an atherosclerotic disease characterized by a narrowing of the artery lumen and a high risk of ischemic stroke. Risk factors of atherosclerosis, including smoking, hypertension, hyperglycemia, hyperlipidemia, aging, and disrupted circadian rhythm, may potentiate atherosclerosis in the carotid artery and further reduce the arterial lumen. Ischemic stroke due to severe CAS and cerebral ischemic/reperfusion (I/R) injury after the revascularization of CAS also adversely affect clinical outcomes. Melatonin is a pluripotent agent with potent anti-inflammatory, anti-oxidative, and neuroprotective properties. Although there is a shortage of direct clinical evidence demonstrating the benefits of melatonin in CAS patients, previous studies have shown that melatonin may be beneficial for patients with CAS in terms of reducing endothelial damage, stabilizing arterial plaque, mitigating the harm from CAS-related ischemic stroke and cerebral I/R injury, and alleviating the adverse effects of the related risk factors. Additional pre-clinical and clinical are required to confirm this speculation.

Melatonin mitigates the adverse effect of hypoxia during myocardial differentiation in mouse embryonic stem cells

Background

Hypoxia causes oxidative stress and affects cardiovascular function and the programming of cardiovascular disease. Melatonin promotes antioxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione peroxidase, and catalase.

Objectives

This study aims to investigate the correlation between melatonin and hypoxia induction in cardiomyocytes differentiation.

Methods

Mouse embryonic stem cells (mESCs) were induced to myocardial differentiation. To demonstrate the influence of melatonin under hypoxia, mESC was pretreated with melatonin and then cultured in hypoxic condition. The cardiac beating ratio of the mESC-derived cardiomyocytes, mRNA and protein expression levels were investigated.

Results

Under hypoxic condition, the mRNA expression of cardiac-lineage markers (Brachyury, Tbx20, and cTn1) and melatonin receptor (Mtnr1a) was reduced. The mRNA expression of cTn1 and the beating ratio of mESCs increased when melatonin was treated simultaneously with hypoxia, compared to when only exposed to hypoxia. Hypoxia-inducible factor (HIF)-1α protein decreased with melatonin treatment under hypoxia, and Mtnr1a mRNA expression increased. When the cells were exposed to hypoxia with melatonin treatment, the protein expressions of phospho-extracellular signal-related kinase (p-ERK) and Bcl-2-associated X proteins (Bax) decreased, however, the levels of phospho-protein kinase B (p-Akt), phosphatidylinositol 3-kinase (PI3K), B-cell lymphoma 2 (Bcl-2) proteins, and antioxidant enzymes including Cu/Zn-SOD, Mn-SOD, and catalase were increased. Competitive melatonin receptor antagonist luzindole blocked the melatonin-induced effects.

Conclusions

This study demonstrates that hypoxia inhibits cardiomyocytes differentiation and melatonin partially mitigates the adverse effect of hypoxia in myocardial differentiation by regulating apoptosis and oxidative stress through the p-AKT and PI3K pathway.

Effects of melatonin on cadmium accumulation and haematological parameters in cadmium intoxicated Prussian carp (Carassius gibelio B.)

The present study was performed to determine the effect of melatonin on cadmium accumulation and haematological parameters changes in females of Prussian carp (Carassius gibelio B.). The fish were exposed to a sublethal concentration of cadmium (0.4 and 4.0 mg/L) without or with melatonin implant (containing 18 mg melatonin hormone) for 1, 4, 7, 10 and 13 weeks. After the 7th week, Cd-exposed fish were divided into two groups. The first group of fish were subjected to depuration in clear water, while the second group remained exposed to the same concentrations of cadmium. After the 10th and 13th weeks of exposure the kidney, spleen, heart and blood were taken in order to determine the cadmium concentration and to analyse haematological parameters. The results of this study showed an increase in the concentration of cadmium in the tissues and blood in fish exposed to the highest dose (4.0 mg/L) of cadmium in water with a dependence on the exposure duration. Additionally, it was shown that melatonin administration reduced the cadmium concentration in the tissues and blood, and melatonin had a protective effect against cadmium accumulation. Moreover, the results showed a significant increase in blood parameters (RBC, Ht and Hb) in fish treated with the highest dose of cadmium. However, implantation of melatonin in cadmium-treated fish resulted in marked improvements in haematological parameters. Thus, melatonin can be a good implementation to alleviate, at least partially, the toxicity of cadmium.

Effect of melatonin on heart failure: design for a double-blinded randomized clinical trial

AIMS

Current studies indicate that melatonin can counteract renin-angiotensin-aldosterone system and sympathetic over activity in heart failure (HF) and might have a protective and repairing effect on cardiovascular injuries, skeletal muscle weakness, and metabolic abnormalities, which are common pathological processes in patients with HF. The MeHR trial (Melatonin for Heart Failure with Reduced Ejection Fraction) aims to evaluate the effect of oral melatonin on myocardial, skeletal muscle, and metabolic dysfunctions in HF, which leads to lower quality of life and increased morbidity and mortality in these patients.

METHODS AND RESULTS

This is a double-blind randomized clinical trial with two parallel arms of 1:1 allocation, which recruits 90 outpatients with HF with reduced ejection fraction. Participants receive 10 mg tablets of melatonin or placebo for 24 weeks. The primary outcomes are changes in echocardiographic indexes of HF and serum levels of N terminal pro brain natriuretic peptide. Secondary outcome is a composite clinical endpoint score including all-cause mortality, hospitalization for HF, and change in the quality of life during the study. Other outcomes are the evaluation of melatonin attributable adverse effects, flow-mediated vasodilation, skeletal muscle mass, exercise capacity, and serum markers of inflammation, oxidative stress, and metabolism. Statistical analysis will include simple unadjusted analyses for the detection of differences between groups and changes in outcomes and also a generalized linear mixed model to explore potential associations between outcomes and participant characteristics.

CONCLUSIONS

The results of this comprehensive study might elucidate the safety of oral melatonin in patients with HF and provide some evidence on its effectiveness as an adjunctive therapy to enhance the well-being of these patients.

Ionizing Radiation as a Source of Oxidative Stress-The Protective Role of Melatonin and Vitamin D

Ionizing radiation (IR) has found widespread application in modern medicine, including medical imaging and radiotherapy. As a result, both patients and healthcare professionals are exposed to various IR doses. To minimize the negative side effects of radiation associated with oxidative imbalance, antioxidant therapy has been considered. In this review, studies on the effects of melatonin and vitamin D on radiation-induced oxidative stress are discussed. According to the research data, both substances meet the conditions for use as agents that protect humans against IR-induced tissue damage. Numerous studies have confirmed that melatonin, a hydro- and lipophilic hormone with strong antioxidant properties, can potentially be used as a radioprotectant in humans. Less is known about the radioprotective effects of vitamin D, but the results to date have been promising. Deficiencies in melatonin and vitamin D are common in modern societies and may contribute to the severity of adverse side effects of medical IR exposure. Hence, supporting supplementation with both substances seems to be of first importance. Interestingly, both melatonin and vitamin D have been found to selectively radiosensitise cancer cells, which makes them promising adjuvants in radiotherapy. More research is needed in this area, especially in humans.

Infusion of Melatonin Into the Paraventricular Nucleus Ameliorates Myocardial Ischemia-Reperfusion Injury by Regulating Oxidative Stress and Inflammatory Cytokines

Melatonin, the receptors for which are abundant in the hypothalamic paraventricular nucleus (PVN), can protect the heart from myocardial ischemia–reperfusion (MI/R) injury. The aim of this study was to determine whether the infusion of melatonin into the PVN protects the heart from MI/R injury by suppressing oxidative stress or regulating the balance between proinflammatory cytokines and anti-inflammatory cytokines in MI/R rats. Male Sprague–Dawley rats were treated with a bilateral PVN infusion of melatonin. MI/R operation was performed 1 week after infusion. At the end of the third week after the infusion, all the rats were euthanized. This was followed by immunohistochemistry and immunofluorescence studies of the rats. MI/R rats showed larger infarct size, increased left ventricular (LV) end-diastolic volume, and decreased LV ejection fraction and LV fractional shortening. Moreover, MI/R rats had a higher level of norepinephrine in the plasma, heart, and PVN; higher PVN levels of reactive oxygen species, NOX2, NOX4, IL-1β, and NF-κB activity; and lower PVN levels of copper/zinc superoxide dismutase (Cu/Zn-SOD) and IL-10 compared with the sham group. Melatonin infusion in PVN reduced LV end-diastolic volume, norepinephrine, reactive oxygen species, NOX2, NOX4, IL-1β, and NF-κB activity, and increased LV ejection fraction, LV fractional shortening, Cu/Zn-SOD, and IL-10. Overall, these results suggest that the infusion of melatonin ameliorates sympathetic nerve activity and MI/R injury by attenuating oxidative stress and inflammatory cytokines in the PVN of MI/R rats.

To beer or not to beer: A meta-analysis of the effects of beer consumption on cardiovascular health

A moderate alcohol consumption is demonstrated to exert a protective action in terms of cardiovascular risk. Although this property seems not to be beverage-specific, the various composition of alcoholic compounds could mediate peculiar effects in vivo. The aim of this study was to evaluate potential beer-mediated effects on the cardiovascular health in humans, using a meta-analytic approach (trial registration number: CRD42018118387). The literature search, comprising all English articles published until November, 30th 2019 in EMBASE, PubMed and Cochrane database included all controlled clinical trials evaluating the cardiovascular effects of beer assumption compared to alcohol-free beer, water, abstinence or placebo. Both sexes and all beer preparations were considered eligible. Outcome parameters were those entering in the cardiovascular risk charts and those related to endothelial dysfunction. Twenty-six trials were included in the analysis. Total cholesterol was significantly higher in beer drinkers compared to controls (14 studies, 3.52 mg/dL, 1.71–5.32 mg/dL). Similar increased levels were observed in high-density lipoprotein (HDL) cholesterol (18 studies, 3.63 mg/dL, 2.00–5.26 mg/dL) and in apolipoprotein A1 (5 studies, 0.16 mg/dL, 0.11–0.21 mg/dL), while no differences were detected in low density lipoprotein (LDL) cholesterol (12 studies, -2.85 mg/dL, -5.96–0.26 mg/dL) and triglycerides (14 studies, 0.40 mg/dL, -5.00–5.80 mg/dL) levels. Flow mediated dilation (FMD) resulted significantly higher in beer-consumers compared to controls (4 studies, 0.65%, 0.07–1.23%), while blood pressure and other biochemical markers of inflammation did not differ. In conclusion, the specific beer effect on human cardiovascular health was meta-analysed for the first time, highlighting an improvement of the vascular elasticity, detected by the increase of FMD (after acute intake), and of the lipid profile with a significant increase of HDL and apolipoprotein A1 serum levels. Although the long-term effects of beer consumption are not still understood, a beneficial effect of beer on endothelial function should be supposed.

Cardioprotective effects of melatonin: Focusing on its roles against diabetic cardiomyopathy

Melatonin is a pineal-produced indole known for its anti-aging, antiapoptotic and antioxidant properties. In past decades, the protective potentials of melatonin for cardiovascular diseases, such as atherosclerosis and myocardial infarction, have been widely revealed, triggering more investigations focused on other cardioprotective effects of melatonin. Recently, the roles of melatonin in diabetic cardiomyopathy (DCM) have attracted increased attention. In this regard, researchers found that melatonin attenuated cardiac fibrosis and hypertrophy, thus interrupting the development of DCM. Retinoid-related orphan receptor α is a key melatonin receptor that contributed to the cardioprotective effect of melatonin in hearts with DCM. For the downstream mechanisms, the inhibition of mammalian STE20-like kinase 1 plays a pivotal role, which exerts antiapoptotic and proautophagic effects, thus enhancing cardiac tolerance in high-glucose conditions. In addition, other signalling mechanisms, such as sirtuin-1/peroxisome proliferator-activated receptor gamma-coactivator alpha and endoplasmic reticulum-related signalling, are also involved in the protective effects of melatonin on cardiomyocytes under diabetic conditions. This review will focus on the protective signalling mechanisms regulated by melatonin and provide a better understanding of the therapeutic applications of melatonin signalling in DCM.

Melatonin ameliorates periodontitis-related inflammatory stress at cardiac left ventricular tissues in rats

BACKGROUND

The aim of this experimental rat study was to investigate the potential inflammatory effects of periodontitis on cardiac left ventricular tissue and the therapeutic activity of melatonin on these effects.

METHODS

Twenty-four male Sprague-Dawley rats were randomly divided into three groups: control, experimental periodontitis (Ep), and Ep-melatonin (Ep-Mel). Experimental periodontitis was induced by placing and maintaining 3.0 silk ligatures at a peri marginal position on the left and right mandibular first molars for 5 weeks. Afterward, following the removal of ligatures, melatonin (10 mg/body weight) to Ep-Mel group, and vehicle (saline) to Ep and control groups were administered intraperitoneally for 14 days. On the first day of the eighth week, mandibular and cardiac left ventricular tissue samples were obtained following the euthanasia of the rats in all groups. Alveolar bone loss measurements were made on histological and microcomputed tomographic slices. Cardiac tissue levels of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), matrix metalloproteinase-9 (MMP-9), and cardiac Troponin-T (cTnT) were evaluated by appropriate biochemical methods.

RESULTS

Measurements made on the histological and microcomputed tomographic slices showed that melatonin significantly limits the ligature-induced periodontal tissue destruction (P <0.01). In addition, melatonin was detected to cause a significant decrease of MDA, MMP-9, and cTnT levels which were found to be significantly higher on rats with Ep (P <0.05) while having no significant effect on antioxidant levels (GSH, SOD, and CAT) (P >0.05).

CONCLUSION

Melatonin might be regarded as an important supportive therapeutic agent to reduce the early degenerative changes and possible hypertrophic remodeling at cardiac left ventricular tissues provoked by periodontitis-related bacteria and/or periodontal inflammation.

Melatonin fine-tunes intracellular calcium signals and eliminates myocardial damage through the IP3R/MCU pathways in cardiorenal syndrome type 3

Cardiorenal syndrome type-3 (CRS-3) is characterized by acute cardiac injury induced by acute kidney injury. Here, we investigated the causes of CRS-3 by analyzing cardiac function after renal ischemia-reperfusion injury (IRI) using echocardiography and evaluation of pro-inflammatory markers, calcium balance, mitochondrial function, and cardiomyocyte death. Our results show that renal IRI reduces cardiac diastolic function associated with cardiomyocyte death and inflammatory responses. Renal IRI also disrupts cardiomyocyte energy metabolism, induces calcium overload, and impairs mitochondrial function, as evidenced by reduced mitochondrial membrane potential and increased mitochondrial fission. Further, renal IRI induces phosphorylation of inositol 1,4,5-trisphosphate receptor (IP3R) and expression of mitochondrial calcium uniporter (MCU), resulting in cytoplasmic calcium overload and mitochondrial calcium accumulation. Pretreatment with melatonin attenuates renal IRI-mediated cardiac damage by maintaining myocardial diastolic function and reducing cardiomyocyte death. Melatonin also inhibits IP3R phosphorylation and MCU expression, thereby alleviating cytoplasmic and mitochondrial calcium overload. Blockade of IP3R has similar cardioprotective effects, whereas MCU activation abrogates the melatonin-mediated cardioprotection. These results show that the negative effects of renal IRI on myocardial viability and cardiac function are caused by induced IP3R phosphorylation, MCU upregulation, and calcium overload. Melatonin protects cardiac function against CRS-3 by suppressing IP3R-MCU signaling.

New Insights Into the Evolutionary History of Melatonin Receptors in Vertebrates, With Particular Focus on Teleosts

In order to improve our understanding of melatonin signaling, we have reviewed and revised the evolutionary history of melatonin receptor genes (mtnr) in vertebrates. All gnathostome mtnr genes have a conserved gene organization with two exons, except for mtnr1b paralogs of some teleosts that show intron gains. Phylogeny and synteny analyses demonstrate the presence of four mtnr subtypes, MTNR1A, MTNR1B, MTNR1C, MTNR1D that arose from duplication of an ancestral mtnr during the vertebrate tetraploidizations (1R and 2R). In tetrapods, mtnr1d was lost, independently, in mammals, in archosaurs and in caecilian amphibians. All four mtnr subtypes were found in two non-teleost actinopterygian species, the spotted gar and the reedfish. As a result of teleost tetraploidization (3R), up to seven functional mtnr genes could be identified in teleosts. Conservation of the mtnr 3R-duplicated paralogs differs among the teleost lineages. Synteny analysis showed that the mtnr1d was conserved as a singleton in all teleosts resulting from an early loss after tetraploidization of one of the teleost 3R and salmonid 4R paralogs. Several teleosts including the eels and the piranha have conserved both 3R-paralogs of mtnr1a, mtnr1b, and mtnr1c. Loss of one of the 3R-paralogs depends on the lineage: mtnr1ca was lost in euteleosts whereas mtnr1cb was lost in osteoglossomorphs and several ostariophysians including the zebrafish. We investigated the tissue distribution of mtnr expression in a large range of tissues in medaka. The medaka has conserved the four vertebrate paralogs, and these are expressed in brain and retina, and, differentially, in peripheral tissues. Photoperiod affects mtnr expression levels in a gene-specific and tissue-specific manner. This study provides new insights into the repertoire diversification and functional evolution of the mtnr gene family in vertebrates.

Advances in Characterizing Recently-Identified Molecular Actions of Melatonin: Clinical Implications

Melatonin, N-acetyl-5-methoxy-tryptamine, was discovered to be a product of serotonin metabolism in the mammalian pineal gland where its synthesis is under control of the light:dark cycle. Besides its regulatory pathway involving ganglion cells in the retina, the neural connections between the eyes and the pineal gland include the master circadian clock, the suprachiasmatic nuclei, and the central and peripheral nervous systems. Since pineal melatonin is released into the blood and into the cerebrospinal fluid, it has access to every cell in an organism and it mediates system-wide effects. Subsequently, melatonin was found in several extrapineal organs and, more recently, perhaps in every cell of every organ. In contrast to the pinealocytes, non-pineal cells do not discharge melatonin into the blood; rather it is used locally in an intracrine, autocrine, or paracrine manner. Melatonin levels in non-pineal cells do not exhibit a circadian rhythm and do not depend on circulating melatonin concentrations although when animals are treated with exogenous melatonin it is taken up by presumably all cells. Mitochondria are the presumed site of melatonin synthesis in all cells; the enzymatic machinery for melatonin synthesis has been identified in mitochondria. The association of melatonin with mitochondria, because of its ability to inhibit oxidative stress, is very fortuitous since these organelles are a major site of damaging reactive oxygen species generation. In this review, some of the actions of non-pineal-derived melatonin are discussed in terms of cellular and subcellular physiology.