The Impact of Melatonin in Research

Yet another in vitro evidence that natural compounds introduced by diet have anti-amyloidogenic activities and can counteract neurodegenerative disease depending on aging

A major issue in Alzheimer's disease (AD) research is to find some new therapeutic drug which decrease Amyloid-beta (Aβ) aggregation. From a therapeutic point of view the major question is whether pharmacological inhibition of inflammation pathways will be able to safely reverse or slow the course of disease. Natural compounds are capable of binding to different targets implicated in AD and exert neuroprotective effects. Aim of this study was to evaluate the in vitro inhibition of Aβ1-42 fibrillogenesis in presence of Gallic acid, Rutin, Melatonin and ProvinolsTM . We performed the analysis with Transmission and Scanning Electron Microscopy, and with X-ray microanalysis. Samples treated with Rutin, that arises from phenylalanine via the phenylpropanoid pathway, show the best effective result obtained because a significantly fibril inhibition activity is detectable compared to the other compounds. Melatonin shows a better inhibitory activity than ProvinolsTM and Gallic acid at the considered concentrations.

Regulatory role of melatonin in Notch1 signaling pathway in cerebral cortex of Aβ1-42-induced Alzheimer's disease rat model

BACKGROUND

Soluble Amyloid-beta (Aβ) oligomers are thought to play a key role in the pathogenesis of Alzheimer's disease (AD), which is the most common age-associated neurodegenerative diseases with obvious neuropathological changes and functional decline in both cortical and subcortical regions. Melatonin is ubiquitously distributed and multifunctioning indoleamine. Accumulating studies support that melatonin is potential therapeutic molecule for AD through modulating a broad variety of signaling pathways. In recent years, Notch1 signaling pathway is been known involved in dynamic changes in the cellular architecture and function of adult brain, as well as associated with the pathophysiology of AD and other neurodegenerative disorders.

METHODS AND RESULTS

In this study, we performed real-time polymerase chain reaction, immunohistochemistry and western blotting analyses using the cerebral cortical tissues of Aβ_1-42 oligomers-induced AD rats with or without melatonin treatment. Our results showed that soluble Aβ_1-42 oligomers decreased the expression of the main components of Notch1 signaling pathway, Notch1, NICD and Hes1 in the cerebral cortex, and melatonin could restore the level of Notch1, NICD and Hes1.

CONCLUSION

This observation suggests that targeting of Notch1 signaling might be a promising therapeutic approach for AD and other age-associated neurodegenerative diseases, and melatonin might serve as a potential therapeutic agent for AD and other age-associated neurodegenerative diseases.

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.

Immunolocalization of melatonin receptors in bovine ovarian follicles and in vitro effects of melatonin on growth, viability and gene expression in secondary follicles

This study aims to investigate the (1) expression of melatonin receptors types 1A/B (MTNR1A/B) in bovine ovaries and (2) the in vitro effects of melatonin on secondary follicle development, antrum formation, viability, and expression of messenger ribonucleic acid (mRNA) for superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase-1 (GPX1) and peroxiredoxin 6 (PRDX6). The expression of MTNR1A/B in bovine ovarian follicles was demonstrated by immunohistochemistry. To choose the most effective concentration of melatonin on follicular growth and viability, isolated secondary follicles were cultured individually at 38.5°C, with 5% CO₂ in air, for 18 d in TCM-199⁺ alone or supplemented with 10^-11, 10^-9, 10^-7 or 10^-5 M melatonin. Then, melatonin receptor antagonist, luzindole, was tested to further evaluate the mechanisms of actions of melatonin, that is, the follicles were cultured in control medium alone or supplemented with 10^-7 M melatonin, 10 µM luzindole and both 10^-7 M melatonin and 10 µM luzindole. Follicular growth, morphology and antrum formation were evaluated at days 6, 12 and 18. At the end of culture, viability of secondary follicles was analyzed by calcein-AM and ethidium homodimer-1, and the relative levels of mRNA for SOD, CAT, GPX1 and PRDX6 were evaluated by real time polymerase chain reaction. Immunohistochemistry results showed expression of MTNR1A/B in oocyte and granulosa cells of primordial, primary, secondary and antral follicles. Secondary follicles cultured in medium supplemented with melatonin at different concentrations had well preserved follicles after 18 d of culture. Furthermore, follicles cultured in presence of 10^-7 M melatonin presented significantly higher diameters than those cultured in other treatments. The presence of melatonin receptor antagonist, luzindole, blocked the effects of melatonin on follicular growth and viability. In addition, follicles cultured in medium containing only melatonin had significantly higher rates of antrum formation. Follicles cultured in medium containing only melatonin had higher relative levels of mRNA for CAT, SOD and PRDX-6 than those cultured with both melatonin and luzindole. Follicles cultured with luzindole only or both melatonin and luzindole had lower relative levels of mRNA for PRDX6 and GPX1 than those cultured control medium. In conclusion, melatonin promotes growth of bovine secondary follicles through its membrane-coupled receptors, while luzindole blocks the effects of melatonin on follicle growth and reduces the expression of antioxidant enzymes in cultured follicles.

Response to Treatment with Melatonin and Clonazepam versus Placebo in Patients with Burning Mouth Syndrome

Objective: to evaluate the efficacy of melatonin and clonazepam versus placebo in patients with burning mouth syndrome (BMS). Methods: a prospective double-blind study was carried out in patients with BMS and randomized to three groups: melatonin (1 mg once a day), clonazepam (0.5 mg/twice a day), or a placebo once a day, for 8 weeks. The clinical changes were evaluated, including xerostomia, the Oral Health Impact Profile 14 (OHIP-14) score, Pittsburg Sleep Quality Index, and the Hospital Anxiety and Depression Scale (HADS). Oxygen saturation and heart rate were recorded, with an analysis of salivary biomarkers in the forms of oxytocin, ferritin, adenosine deaminase (ADA), total proteins, and alpha-amylase. Results: a total of 64 patients were analyzed. A significant decrease in burning sensation was recorded with melatonin (7.8 ± 1.54 pre-treatment, 5.78 ± 2.54 post-treatment; p < 0.001) and clonazepam (8.75 ± 1.2 pre-treatment, 5.5 ± 3.6 post-treatment (p < 0.01). With regard to quality of life (OHIP-14), significant improvements were observed before and after the administration of melatonin (p < 0.001) and clonazepam (p = 0.001). On the other hand, with regard to the changes in salivary biomarkers following treatment, negative correlations were found between oxytocin and drainage (r = −0.410; p = 0.009) and between the HADS-D score and ferritin (r = −0.312; p = 0.05). While salivary amylase showed positive correlation with heart rate (r = 0.346; p = 0.029) and oxygen saturation (r = 0.419; p = 0.007). Conclusions: melatonin and clonazepam were shown to be effective at reducing the burning sensation and improving quality of life. Both drugs were found to be safe, with no major adverse effects in patients with BMS. Melatonin may be regarded as an alternative treatment for patients with BMS, though further studies are needed to confirm its effectiveness.

Role of mast cells in skin regeneration after thermal burn treated with melatonin-enriched dermal film

The development of novel local therapies for thermal burns (TB) and their pathogenetic rationale are a pressing challenge. Melatonin (MT) is an endogenous factor of hemostasis regulation with pleiotropic potential. The aim of this study was to assess some parameters of tissue regeneration, the functional state of mast cells and the levels of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) in the experimentally induced TB treated with the original MT-enriched dermal film (DF). A second-degree burn (3.5% of the total body surface area) was modelled by exposing a patch of skin to hot water. Applications of 12 cm2 DF enriched with 5 mg/g MT were performed every day for 5 days. The following parameters were calculated: the wound area, the rate of wound epithelization, the number of MC in the wound, the intensity of degranulation, and the levels of MMP-9 and VEGF expression. Over the course of treatment, the absolute wound area shrank by 35%, its epithelization rate increased, the number of MC rose, their functional state changed, and the expression of ММР-9 and VEGF increased. A negative correlation was established between the wound area and the expression of ММР-9 and VEGF, as well as between the wound area and the degranulation coefficient. Applications of MT-enriched DF resulted in the reduction of the wound area, higher epithelization rate, an increase in the total MC count and degranulation intensity on days 5 and 10; it also led to a reduction in the total MC count and a loss in degranulation intensity on day 20 (166.87 (154.95; 178.78) un/mm2 vs. 464.84 (452.92; 476.76) un/mm2) in the group of intact animals), an increase in MMP-9 expression on day 5 (14.20 (11.30; 18.10) vs. 3.30 (2.20; 4.40) in the intact group), an increase in VEGF expression on days 5 and 10 (33.00 (30.20; 34.90) vs 25.40 (22.20; 29.30) in the intact group), and a reduction in MMP-9 expression on days 10 and 20 after thermal injury.

Research Hot Spots and Trends on Melatonin From 2000 to 2019

Research on melatonin remains one of the major hot spots in the field of disease treatment, but relevant data are numerous. The purpose of this study was to quantitatively and qualitatively analyze the progress of melatonin research through the method of bibliometrics and to predict hot spots and trends in melatonin research. This study retrieved all the studies on melatonin from 2000 to 2019 in the Web of Science and PubMed and analysed the publishing trends in the literature on a bibliometric online analysis platform and CiteSpace software. The research results were also visually analysed to summarize melatonin research hot spots through gCLUTO and pubMR. The study retrieved a total of 20,351 publications, of which the number of US publications ranked first, accounting for 21.46%, with the greatest impact (centrality = 0.31). The University of Texas Health Science Center at San Antonio and Harvard University had the highest average number of citations at 43.19 and 33.96, respectively. Journal of Pineal Research had the highest average number of citations in 2,993 journals. Professor Reiter made the largest contribution to this area. We further analysed 100 highly cited articles for clinical applications and ongoing related clinical drug trials based on the first hot spot. We systematically analysed melatonin for nearly 20 years while predicting the main research trends in the future, which may provide new directions and ideas for melatonin research. The structure and normal physiological functions of melatonin have been intensively studied in the past few years. And clinical application research and target of melatonin treatment for different diseases and target-based drug design will certainly become the focus of melatonin research.

Melatonin-induced suppression of DNA methylation promotes odontogenic differentiation in human dental pulp cells

Differentiation potency of human dental pulp cells (hDPCs) is essential for dentin regeneration. DNA methylation is one of the major epigenetic mechanisms and is suggested to involve in differentiation of hDPCs, the machinery of which includes DNA methyltransferase enzymes (DNMTs) and methyl-CpG-binding domain proteins (MBDs). Our previous study has found that melatonin (MT) promoted hDPC differentiation, but its mechanism remains elusive. We aimed to investigate the role of DNA methylation in the promotion of MT to differentiation of hDPCs in vitro. hDPCs were cultured in basal growth medium (CO) or odontogenic medium (OM) exposed to MT at different concentrations (0, 10-12, 10-10, 10-8, 10-6, 10-4 M). The cell growth was analyzed using Cell Counting Kit-8 assay, and mineralized tissue formation was measured using Alizarin red staining. The expression of the 10 genes (DNMT1, DNMT3A, DNMT3B, MBD1-6, MeCP2) was determined using real-time qPCR and western blotting. The abundance of MeCP2 in the nuclei was evaluated using immunofluorescence analysis. Global methylation level was tested using ELISA. We found that mineralized tissue formation significantly increased in OM with MT at 10-4 M, while the levels of MeCP2 and global DNA methylation level declined. The expression of MBD1, MBD3, and MBD4 significantly increased in OM alone, and the expession of DNMT1 and MBD2 was decreased. These results indicate that MT promotes odontogenic differentiation of hDPCs in vitro by regulating the levels of DNMT1, MeCP2, and global DNA methylation, suggesting that MT-induced DNA methylation machinery may play an important role in tooth regeneration.

Local antioxidant effect of original dermal film with melatonin in thermal injury

Oxidative stress (OS) escalation associated with thermal trauma (TT) and pleiotropic effects of melatonin (MT) suggest a study of protective properties of the latter when applied as part of a novel dermal film (DF) to skin burns. This work aimed to assess the content of OS markers in the skin subjected to experimental TT and treated with DF with MT. Third A degree TT (area of 3.5%) were modeled by immersing a patch of skin in boiling water. Twelve cm2 of DF with 5 mg/g of MT were applied daily for 5 days. The parameters calculated were wound's area and epithelializatiohon rate. The products monitored in the burn wound were lipid peroxidation (LPO) products in heptane and isopropanol phases of the lipid extract and protein oxidative modification (POM) products, the modification being spontaneous and metal-dependent. With TT in the wound, the content of secondary and end LPO products in heptane and isopropanol phases increased on the 5th and 10th days; the total content of POM products grew on the 5th day (primary products, neutral) and on the 10th day (primary and secondary products, neutral). Application of DF to a TT wound reduced the burn area, increased the epithelialization rate (by the 10th day, the median went from 1.90% to 6.57%; p < 0.05), reduced the content of secondary and end LPO products in isopropanol phase (by the 10th day, the median went from 0.007 to 0.004 u.o.i; p < 0.05), reduced the total content of OMP products, namely that of primary neutral products — on the 5th day, of primary and secondary neutral products — on the 10th day. With TT present in the context of MT application, the burn area showed presence of secondary LPO products in heptane and isopropanol phases, LPO end products in isopropanol phase, POM products in the wound (basic and neutral primary/secondary POM products).

Worldwide melatonin research: a bibliometric analysis of the published literature between 2015 and 2019

This study presents a bibliometric analysis of the publications on melatonin research from the Scopus database during the period 2015-2019. Based on the keywords used, which are related to melatonin in the article title, the study retrieved 4411 documents for further analysis using various tools. We used Microsoft Excel to conduct the frequency analysis, VOSviewer for data visualization, and Harzing's Publish or Perish for citation metrics and analysis. This study reports the results using standard bibliometric indicators such as the growth of publications, authorship patterns, collaboration, and prolific authors, country contribution, most active institutions, preferred journals, and top-cited articles. Based on our findings, there is a continuous growth of publications on melatonin research for 5 years since 2015. China was the largest contributor to melatonin research, followed by the United States. The Journal of Pineal Research published the most number of publications related to melatonin research. Our findings suggest that the role of melatonin in plant and food sciences, as well as in cancer, may in later years take over the clusters that earlier dominated melatonin research.

Mechanochemical preparation of molecular and ionic co-crystals of the hormone melatonin

Molecular and ionic co-crystals of melatonin with piperazine, DABCO and CaCl₂ were obtained via kneading with ethanol: the solubility of melatonin in H₂O increases by an order of magnitude when combined with CaCl₂.

Effects of N-acetyl cysteine and melatonin on early reperfusion injury in patients undergoing coronary artery bypass grafting: A randomized, open-labeled, placebo-controlled trial

OBJECTIVES

This study assessed the efficacy of oral consumption of N-acetyl cysteine (NAC) and melatonin (ML) in reducing early reperfusion injury and acute oxidative stress in patients undergoing coronary artery bypass grafting (CABG) with respect to the measurements of cardiac troponin I, lactate, malondealdehyde (MDA), and tumor necrosis factor-α (TNF-α) levels in the blood.

METHODS

This study was a randomized, open-label, placebo-controlled trial. Eighty eight patients, aged between 39 to 76 years and eligible for CABG, were recruited and randomly assigned into 3 intervention groups through a simple randomization method and underwent CABG surgery. Blood samples were withdrawn from arterial line, before the induction of anesthesia (before the start of surgery), after incision (before aortic cross-clamping), during global ischemia (during aortic cross-clamping), after aortic cross-clamping (on set of reperfusion), 15 minutes after reperfusion, and after recovery at the intense care unit. The blood samples were analyzed for troponin I, lactate, MDA and TNF-α levels.

RESULTS

There was no significant difference in influencing variables among the groups at the baseline. Overall mean troponin I, lactate, and TNF- α levels were significantly different between the intervention groups (all P < .001) at the recovery phase. Post-hoc pairwise comparisons showed that the differences of mean serum levels between ML and control groups were statistically significant for MDA, TNF- α, lactate, and troponin I (P < .001, P = .001, and P = .001, respectively). The differences between NAC and control groups and between ML and NAC groups were only significant for mean lactate level (P < .001).

CONCLUSION

The current study revealed that ML and NAC are potent antioxidants with similar efficacy in terms of reducing CABG related cardiac injury and oxidative stress with the dosage employed for the intervention.

Effect of melatonin on bovine theca cells in vitro

Melatonin affects granulosa cell function in several species but its function in theca cells is less clear, particularly in monotocous animals. Thus, the objectives of this study were to determine the effects of melatonin on theca cell steroidogenesis, gene expression and cell proliferation in a monotocous species, namely cattle. Ovaries were collected from a local bovine abattoir, from which theca cells were isolated from large (8–22 mm) follicles and treated with various hormones in serum-free medium for 24 h or 48 h. Melatonin caused a dose-dependent inhibition (P < 0.05) of LH+insulin-like growth factor 1 (IGF1)-induced androstenedione and progesterone production. Also, melatonin inhibited (P < 0.05) LH+IGF1-induced expression of steroidogenic acute regulatory protein (StAR) mRNA (via real-time polymerase chain reaction) in theca cells, but it had no effect (P > 0.10) on cytochrome P450 11A1 (CYP11A1) and cytochrome P450 17A1 (CYP17A1) mRNA abundance. In LH+IGF1-treated theca cells, melatonin decreased caspase 3 (CASP3) mRNA to levels similar to those observed in LH-treated theca cells. In contrast, melatonin increased (P < 0.05) the number of bovine theca cells in both LH- and LH+IGF1-treated cultures. In conclusion, melatonin may act as an endocrine regulator of ovarian function in cattle by stimulating theca cell proliferation and inhibiting differentiation via inhibition of hormone-induced steroidogenesis.

Suppression of Osteoclastogenesis by Melatonin: A Melatonin Receptor-Independent Action

In vertebrates, melatonin is primarily secreted from the pineal gland but it affects various biological processes including the sleep-wake cycle, vasomotor control, immune system and bone homeostasis. Melatonin has been known to promote osteoblast differentiation and bone maturation, but a direct role of melatonin on osteoclast differentiation is still elusive. The present study investigated the effect of melatonin on the differentiation of macrophages to osteoclasts. The presence of melatonin significantly reduced receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis and the siRNA-mediated knockdown of the melatonin receptor failed to overcome the anti-osteoclastogenic effect of melatonin. Although melatonin treatment did not affect the phosphorylation of extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK), it markedly inhibited the activation of NF-κB and subsequent induction of nuclear factor of activated T cell cytoplasmic 1(NFATc1). Thus, our results suggest that melatonin could suppress osteoclast differentiation through downregulation of NF-κB pathway with concomitant decrease in the NFATc1 transcription factor induction. Furthermore, melatonin seems to have an anti-osteoclastogenic effect independent of plasma membrane melatonin receptors. In addition to previously reported properties of melatonin, our study proposes another aspect of melatonin and bone homeostasis.