Melatonin in the oral cavity: physiological and pathological implications

Utility of gingival crevicular fluid components for periodontal diagnosis

Periodontal diseases are highly prevalent chronic diseases, and severe periodontitis creates functional and esthetic problems and decreases self-esteem for a large percentage of the older population worldwide. In many cases of periodontitis, there is no distinct tell-tale pain that motivates a patient to seek treatment, rather the signs become clinically detectable late, and typically when the disease has progressed to a problematic level for the life of the dentition. Early periodontal screening and diagnostics tools will provide early recognition of periodontal diseases and facilitate timely management of the disease to reduce tooth loss. To this goal, gingival crevicular fluid is easily sampled, can be repeatedly and non-invasively collected, and can be tested for potential biomarkers. Moreover, the site specificity of periodontal diseases enhances the usefulness of gingival crevicular fluid sampled from specific sites as a biofluid for diagnosis and longitudinal monitoring of periodontal diseases. The present review aimed to provide up-to-date information on potential diagnostic biomarkers with utility that can be assayed from gingival crevicular fluid samples, focusing on what is new and useful and providing only general historic background textually and in a tabulated format.

Integrating network pharmacology and experimental evaluation to explore the complementary therapeutic effect and mechanism of melatonin in periodontitis

Objective

To explore the potential targets for melatonin in the treatment of periodontitis through network pharmacologic analysis and experimental validation via in vivo animal models and in vitro cellular experiments.

Materials and methods

In this study, we first screened melatonin targets from Pharm Mapper for putative targets, Drug Bank, and TCMSP databases for known targets. Then, disease database was searched and screened for differential expressed genes associated with periodontitis. The intersection of disease and melatonin-related genes yielded potential target genes of melatonin treatment for periodontitis. These target genes were further investigated by protein-protein interaction network and GO/KEGG enrichment analysis. In addition, the interactions between melatonin and key target genes were interrogated by molecular docking simulations. Then, we performed animal studies to validate the therapeutic effect of melatonin by injecting melatonin into the peritoneal cavity of ligation-induced periodontitis (LIP) mice. The effects of melatonin on the predicted target proteins were also analyzed using Western blot and immunofluorescence techniques. Finally, we constructed an in vitro cellular model and validated the direct effect of melatonin on the predicted targets by using qPCR.

Results

We identified 8 potential target genes by network pharmacology analysis. Enrichment analysis suggests that melatonin may treat periodontitis by inhibiting the expression of three potential targets (MPO, MMP8, and MMP9). Molecular docking results showed that melatonin could effectively bind to MMP8 and MMP9. Subsequently, melatonin was further validated in a mouse LIP model to inhibit the expression of MPO, MMP8, and MMP9 in the periodontal tissue. Finally, we verified the direct effect of melatonin on the mRNA expression of MPO, MMP8, and MMP9 in an in vitro cellular model.

Conclusions

Through a combination of network pharmacology and experimental validation, this study provides a more comprehensive understanding of the mechanism of melatonin to treat periodontitis. Our study suggests that MPO, MMP8, and MMP9 as key target genes of melatonin to treat periodontitis. These findings present a more comprehensive basis for further investigation into the mechanisms of pharmacological treatment of periodontitis by melatonin.

Melatonin and oral diseases: possible therapeutic roles based on cellular mechanisms

Oral diseases, including periodontal disorders, oral cancer, periodontitis, and mucositis are the major challenges for both patients and healthcare providers. These conditions often involve inflammation, oxidative stress, and impaired cellular processes, leading to symptoms ranging from discomfort to severe debilitation. Conventional treatments for such oral diseases exhibit constraints, prompting the investigation of innovative therapeutic approaches. Considering the anti-inflammatory, anti-oxidant, and anti-cancer effects of melatonin, this study was carried out to investigate the potential protective effects of melatonin in mitigating the severity of oral diseases. Studies indicate that melatonin influences the differentiation of periodontal stem cells, inhibits oral cancer progression, reduces inflammation associated with periodontitis, and alleviates the severity of oral mucositis. Melatonin has demonstrated potential efficacy in both preclinical and clinical investigations; however, findings are frequently heterogeneous and contingent upon contextual factors. This review provides a comprehensiveoverview of current state of knowledge in this domain, elucidating the multifaceted role that melatonin may assume in combatingoral diseases. Further research should be directed toward determining the most effective dosing, timing, and administration methods for melatonin-based therapies for oral diseases.

Melatonin Mitigates Lead-Induced Oxidative Stress and Modifies Phospholipid Profile in Tobacco BY-2 Suspension Cells

Many studies have shown that melatonin (an indoleamine) is an important molecule in plant physiology. It is known that this indoleamine is crucial during plant stress responses, especially by counteracting secondary oxidative stress (efficient direct and indirect antioxidant) and switching on different defense plant strategies. In this report, we present exogenous melatonin's potential to protect lipid profile modification and membrane integrity in Nicotiana tabacum L. line Bright Yellow 2 (BY-2) cell culture exposed to lead. There are some reports of the positive effect of melatonin on animal cell membranes; ours is the first to report changes in the lipid profile in plant cells. The experiments were performed in the following variants: LS: cells cultured on unmodified LS medium-control; (ii) MEL: BY-2 cells cultured on LS medium with melatonin added from the beginning of culture; (iii) Pb: BY-2 cells cultured on LS medium with Pb2+ added on the 4th day of culture; (iv) MEL+Pb: BY-2 cells cultured on LS medium with melatonin added from the start of culture and stressed with Pb2+ added on the 4th day of culture. Lipidomic analysis of BY-2 cells revealed the presence of 40 different phospholipids. Exposing cells to lead led to the overproduction of ROS, altered fatty acid composition and increased PLD activity and subsequently elevated the level of phosphatidic acid at the cost of dropping the phosphatidylcholine. In the presence of lead, double-bond index elevation, mainly by higher quantities of linoleic (C18:2) and linolenic (C18:3) acids in the log phase of growth, was observed. In contrast, cells exposed to heavy metal but primed with melatonin showed more similarities with the control. Surprisingly, the overproduction of ROS caused of lipid peroxidation only in the stationary phase of growth, although considerable changes in lipid profiles were observed in the log phase of growth-just 4 h after lead administration. Our results indicate that the pretreatment of BY-2 with exogenous melatonin protected tobacco cells against membrane dysfunctions caused by oxidative stress (lipid oxidation), but also findings on a molecular level suggest the possible role of this indoleamine in the safeguarding of the membrane lipid composition that limited lead-provoked cell death. The presented research indicates a new mechanism of the defense strategy of plant cells generated by melatonin.

The effects of melatonin on the viability and osteogenic/odontogenic differentiation of human stem cells from the apical papilla

BACKGROUND

An experimental study was conducted to examine whether melatonin influences osteogenic/odontogenic differentiation of human stem cells derived from the apical papilla (hSCAPs).

MATERIALS AND METHODS

In order to isolate hSCAPs, the undeveloped root of a third molar of a human tooth was used. Melatonin was administered to the experimental groups in an osteogenic medium. No treatment was administered to the control group. The methyl thiazolyl tetrazolium (MTT) assay was performed on days 1, 2, and 3 to assess cell viability (n = 8). A determination of odontogenic/osteogenic differentiation was accomplished using alkaline phosphatase (ALP) activity alizarin red staining (ARS) (n = 6), and the expression of osteogenic genes by real-time polymerase chain reaction (RT-PCR) (n = 3) on days 1, 2, and 7. Evaluation of the data was conducted using SPSS version 18. All experiments were conducted at least three times. The Mann Whitney U test, the ANOVA analysis, Tukey's test, and t-test was implemented to analyze the data (α = 0.05).

RESULTS

After 24 h, 48 h, and 72 h, No significant difference was observed between the control group and the melatonin treatment group in terms of viability of hSCAPs. (from 1 up to 10 µg/ml) (P > 0.05). The assessment of ARS and ALP activity showed that melatonin treatment enhanced osteogenic differentiation of hSCAPs (P < 0.001). Melatonin treatment caused hSCAPs to show an increase of genes related to osteogenic/odontogenic differentiation. These genes included ALP, dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP-1), and bone sialoprotein (BSP) (P < 0.001).

CONCLUSIONS

Melatonin treatment enhanced osteogenic/odontogenic differentiation of hSCAPs with a dose dependent effect on cell viability.

Melatonin: a potential therapeutic approach for the management of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease that primarily affects the exocrine glands and is mainly characterized by sicca symptoms of the eyes and mouth. Approximately 30-50% of pSS patients develop systemic multi-organ disorders including malignant lymphoma. The etiology of pSS is not well understood; growing evidence suggests that uncontrolled immune/inflammatory responses, excessive oxidative stress, defected apoptosis, dysregulated autophagy, exosomes, and exogenous virus infections may participate in the pathogenesis of pSS. There is no ideal therapeutic method for pSS; the management of pSS is mainly palliative, which aims to alleviate sicca symptoms. Melatonin, as the main secretory product of the pineal gland, has been evidenced to show various physiological functions, including effects of immunoregulation, capability of antioxidation, moderation of autophagy, suppressive activities of apoptosis, regulative capacity of exosomes, properties of anti-infection, and improvement of sleep. The beneficial effects of melatonin have been already validated in some autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes mellitus (T1DM), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD). However, our previous research firstly revealed that melatonin might inhibit pathogenic responses of peripheral Th17 and double-negative (DN) T cells in pSS. More importantly, melatonin administration alleviated the development of pSS in animal models with reduced infiltrating lymphocytes, improved functional activity of salivary gland, and decreased production of inflammatory factors as well as autoantibodies. Owing to the important biological properties reported in melatonin are characteristics closely related to the treatment of pSS; the potential role and underlying mechanisms of melatonin in the administration of pSS are certainly worth further investigations. Consequently, the aim of this review is to give a deep insight to the therapeutic potency of melatonin for pSS.

Melatonin ultrastructural localization in mitochondria of human salivary glands

The hormone melatonin was initially believed to be synthesized exclusively by the pineal gland and the enterochromaffin cells, but nowadays its production and distribution were observed in several other tissues and organs. Among others, the ultrastructural localization of melatonin and its receptors has been reported in human salivary glands. In these glands, the fine localization of melatonin in intracellular organelles, above all in mitochondria, remains to be explored comprehensively. Bioptic samples of parotid and submandibular glands were treated to search for melatonin using the immunogold staining method by transmission electron microscopy. Morphometric analysis was applied to micrographs. The results indicated that, both in parotid and submandibular glands mitochondria, a certain melatonin positivity was present. Within glandular cells, melatonin was less retrieved in mitochondria than in secretory granules; however, its presence in this organelle was clearly evident. Inside striated duct cells, melatonin staining in mitochondria was more prominent than in glandular cells. Our data provide an ultrastructural report on the presence of melatonin in mitochondria of human major salivary glands and represent a fundamental prerequisite for a better understanding of the melatonin role in this organelle.

Concentrated Growth Factors (CGF) Combined with Melatonin in Guided Bone Regeneration (GBR): A Case Report

During implant restorative dentistry, common and crippling postoperative complications are pain and swelling of perioral soft tissues which engraving on patient quality of life. Concentrated growth factors (CGF), a novel generation of autologous platelet concentrate, and melatonin, endogenous indoleamine with also bone regenerative properties, may be useful for reconstruction of bony defects as well as in prosthetic and esthetic rehabilitation. We report a clinical case in which guided bone regeneration was performed combining CGF, melatonin and heterologous biomaterial. Great postoperative recovery without any complications was reported. In conclusion, in restorative dentistry the combined use of CGF and melatonin may have important roles in restoring bone defect, in improving implant osteointegration and, not less important, in preventing postoperative complications.

Melatonin alleviates the immune response and improves salivary gland function in primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease that primarily affects exocrine glands and is characterized by sicca syndrome and systemic manifestation. Mounting evidence indicates that circadian clocks are involved in the onset and progression of autoimmune diseases, including rheumatic arthritis, multiple sclerosis, and systemic lupus erythematosus. However, few studies have reported the expression of clock genes in pSS. There is no ideal therapeuticmethod for pSS, the management of pSS is mainly palliative, aims to alleviate sicca symptoms. Melatonin is a neuroendocrine hormone mainly secreted by the pineal gland that plays an important role in the maintenance of the circadian rhythm and immunomodulation. Hence, this study aimed to analyse the circadian expression profile of clock genes in pSS, and further evaluate the therapeutic potential of melatonin in pSS. We discovered a distinct clock gene expression profile in an animal model and in patients with pSS. More importantly, melatonin administration regulated clock gene expression, improved the hypofunction of the salivary glands, and inhibited inflammatory development in animal model of pSS. Our study suggested that the pathogenesis of pSS might correlate with abnormal expression of circadian genes, and that melatonin might be a potential candidate for prevention and treatment of pSS.

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.

A Computational Text Mining-Guided Meta-Analysis Approach to Identify Potential Xerostomia Drug Targets

Xerostomia (subjective complaint of dry mouth) is commonly associated with salivary gland hypofunction. Molecular mechanisms associated with xerostomia pathobiology are poorly understood, thus hampering drug development. Our objectives were to (i) use text-mining tools to investigate xerostomia and dry mouth concepts, (ii) identify associated molecular interactions involving genes as candidate drug targets, and (iii) determine how drugs currently used in clinical trials may impact these genes and associated pathways. PubMed and PubMed Central were used to identify search terms associated with xerostomia and/or dry mouth. Search terms were queried in pubmed2ensembl. Protein–protein interaction (PPI) networks were determined using the gene/protein network visualization program search tool for recurring instances of neighboring genes (STRING). A similar program, Cytoscape, was used to determine PPIs of overlapping gene sets. The drug–gene interaction database (DGIdb) and the clinicaltrials.gov database were used to identify potential drug targets from the xerostomia/dry mouth PPI gene set. We identified 64 search terms in common between xerostomia and dry mouth. STRING confirmed PPIs between identified genes (CL = 0.90). Cytoscape analysis determined 58 shared genes, with cytokine–cytokine receptor interaction representing the most significant pathway (p = 1.29 × 10⁻²³) found in the Kyoto encyclopedia of genes and genomes (KEGG). Fifty-four genes in common had drug interactions, per DGIdb analysis. Eighteen drugs, targeting the xerostomia/dry mouth PPI network, have been evaluated for xerostomia, head and neck cancer oral complications, and Sjögren’s Syndrome. The PPI network genes IL6R, EGFR, NFKB1, MPO, and TNFSF13B constitute a possible biomarker signature of xerostomia. Validation of the candidate biomarkers is necessary to better stratify patients at the genetic and molecular levels to facilitate drug development or to monitor response to treatment.

Parameters of Oxidative Stress, Vitamin D, Osteopontin, and Melatonin in Patients with Lip, Oral Cavity, and Pharyngeal Cancer

Lip, oral cavity, and pharyngeal cancers (LOCP) constitute a group of rare neoplasms with unfavorable prognosis. So far, not much is known about the role of vitamin D and oxidative stress in the pathogenesis of LOCP in the European population. The aim of the study was to determine the concentrations of vitamin D, osteopontin, melatonin, and malondialdehyde (MDA) as markers of oxidative stress and/or inflammation, as well as the activities of antioxidant enzymes in the course of LOCP. The vitamin D, melatonin, and osteopontin concentrations in blood serum, the MDA levels in erythrocytes and blood plasma, and the activities of superoxide dismutase (SOD-1), catalase (CAT), and glutathione peroxidase (GPx) in erythrocytes were measured in blood samples taken from 25 LOCP patients of middle age (YCG), 20 LOCP elderly patients (OCG), and 25 healthy middle-aged volunteers. In both cancer groups, decreases in vitamin D and CAT, as well as increases in osteopontin and blood plasma MDA, were observed. An increase in GPx activity in YCG and a decrease in melatonin level in OCG were found. The results indicate the vitamin D deficiency and disturbed oxidant-antioxidant homeostasis in LOCP patients. Osteopontin seems to be associated with LOCP carcinogenesis and requires further research.

Melatonin Suppresses Oral Squamous Cell Carcinomas Migration and Invasion through Blocking FGF19/FGFR 4 Signaling Pathway

Oral squamous cell carcinomas (OSCCs) are one of the most prevalent malignancies, with a low five-year survival rate, thus warranting more effective drugs or therapy to improve treatment outcomes. Melatonin has been demonstrated to exhibit oncostatic effects. In this study, we explored the anti-cancer effects of melatonin on OSCCs and the underlying mechanisms. A human tongue squamous cell carcinoma cell line (SCC-15) was treated with 2 mM melatonin, followed by transwell migration and invasion assays. Relative expression levels of Fibroblast Growth Factor 19 (FGF19) was identified by Cytokine Array and further verified by qPCR and Western blot. Overexpression and downregulation of FGF19 were obtained by adding exogenous hFGF19 and FGF19 shRNA lentivirus, respectively. Invasion and migration abilities of SCC-15 cells were suppressed by melatonin, in parallel with the decreased FGF19/FGFR4 expression level. Exogenous hFGF19 eliminated the inhibitory effects of melatonin on SCC-15 cells invasion and migration, while FGF19 knocking-down showed similar inhibitory activities with melatonin. This study proves that melatonin suppresses SCC-15 cells invasion and migration through blocking the FGF19/FGFR4 pathway, which enriches our knowledge on the anticancer effects of melatonin. Blocking the FGF19/FGFR4 pathway by melatonin could be a promising alternative for OSCCs prevention and management, which would facilitate further development of novel strategies to combat OSCCs.

Effects of melatonin receptor expression on prognosis and survival in oral squamous cell carcinoma patients

Melatonin receptors can inhibit breast and prostate cancers; however, little is known regarding their effects on oral squamous cell carcinoma. In this study, we collected specimens from 81 patients with oral squamous cell carcinoma and analysed clinicopathological data retrospectively. In addition, the expression of the melatonin receptor was analysed immunohistochemically. Survival rates were calculated using the Kaplan-Meier method and log-rank test. Multivariate analysis was performed based on the Cox proportional-hazards model. Further, an in vitro study was performed using YD15 cells. The cells were transfected with siRNA targeting melatonin receptor 1A and 1B for evaluating the malignancy of melatonin receptors by western blotting, trypan blue-exclusion, colony-forming, wound-healing, and invasion assays. Survival decreased as melatonin receptor expression and clinical and pathological tumour-node-metastasis stages increased. A Cox proportional-hazard model showed that melatonin receptor 1A may serve as a significant predictor of the survival rate of patients with oral squamous cell carcinoma [hazard ratio = 1.423, 95% confidence interval (CI) = 1.019-1.988, p = 0.038]. Melatonin receptor 1A and 1B knockdown significantly suppressed proliferation, migration ability, and invasion ability of YD15 cells in vitro. Our findings reveal that inhibiting melatonin receptor expression may suppress oral squamous cell carcinoma development.

The Effect of Melatonin on Periodontitis

BACKGROUND

Periodontitis is a chronic disease with a complex etiology that includes bacterial colonization, excessive inflammation, and oxidative stress. The hormone melatonin has antioxidant properties and might contribute to alleviating chronic conditions by reducing oxidative stress. The aim of this study was to analyze the effect of exogenous melatonin on periodontitis in an animal model of the disease as well as in patients with periodontitis.

METHODS

In rats with ligature-induced periodontitis, melatonin was administered in drinking water for two weeks. In the human study, patients with treatment-resistant periodontitis were asked to rinse their mouths with a solution containing melatonin or placebo every evening for two weeks. Periodontal status as well as salivary markers of oxidative stress were assessed at the end of the study.

RESULTS

Neither radiography nor μCT revealed any significant effects of melatonin on alveolar bone loss. Gum recession was the only improved macroscopic measure in rats (p < 0.05). Analysis of salivary markers of oxidative stress revealed no effects of treatment in rats or humans despite clearly elevated melatonin concentrations in melatonin treated groups.

CONCLUSION

Our results do not support the use of melatonin for the treatment of periodontitis. However, the negative outcome is limited by the short duration of the study and the chosen route of application as well as the dose of melatonin.

Glutaryl Melatonin Niosome Gel for Topical Oral Mucositis: Anti- Inflammatory and Anticandidiasis

BACKGROUND

Glutaryl melatonin, which is synthesized from melatonin and is a pineal glandderived neurohormone with anti-inflammatory and anti-oxidant properties, was comparatively investigated for its potential use as a topical anti-inflammatory agent.

OBJECTIVE

Glutaryl melatonin, synthesized and screened for in vitro anti-candidiasis and in vitro and in vivo anti-inflammatory activities, was formulated as a niosome gel for topical oral evaluation in 5- fluorouracil-induced oral mucositis in mice.

METHODS

In vitro anti-fungal activity in Candida albicans, in vitro anti-inflammatory activity in Escherichia coli liposaccharide-induced RAW cells and in vivo anti-inflammatory activity using a croton oilinduced ear edema model in ICR mice were investigated. Mucositis in mice (n= 6/group, 10-week-old mice) was induced by intraperitoneal injections of 5-fluorouracil, and the mice were subjected to a topical oral application of niosome gel containing melatonin (2% w/w) or glutaryl melatonin (2% w/w) and were compared with mice subjected to blank, fluocinolone acetonide (0.5% w/w) and control conditions.

RESULTS

Glutaryl melatonin, at a 14.2 mM concentration, showed the highest fungicidal effect on C. albicans using the broth dilution method, indicating a nonsignificant difference from 1 μM of nystatin (p = 0.05). Nitric oxide, interleukin-6 and tumor necrosis factors were analyzed by ELISA. Liposaccharide-induced RAW cells were significantly reduced by glutaryl melatonin (p < 0.01). Ear edema inhibition of glutaryl melatonin was significant 1 h after application compared with that of melatonin (p = 0.03). Food consumption and body weight of the 5-fluorouracil-treated mice were significantly lower than those of the normal mice before all treatments (p < 0.05). Differences in the amount of licking behavior, which were observed in the control group for 5 min, were noticeable in the 5- fluorouracil-treated mice but not in the mice treated with the glutaryl melatonin niosome gel.

CONCLUSION

Glutaryl melatonin exhibited mild anti-candidiasis and anti-inflammatory properties. The incorporation of glutaryl melatonin in a niosome gel formulation, demonstrated the potential for topical oral applications to reduce oral discomfort caused by 5-fluorouracil treatment in mice.

Melatonin Treatment Alters Biological and Immunomodulatory Properties of Human Dental Pulp Mesenchymal Stem Cells via Augmented Transforming Growth Factor Beta Secretion

INTRODUCTION

Melatonin is an endogenous neurohormone with well-reported anti-inflammatory and antioxidant properties, but the direct biological and immunomodulatory effects of melatonin on human dental pulp stem cells (hDPSCs) has not been fully elucidated. The aim of this study was to evaluate the influence of melatonin on the cytocompatibility, proliferation, cell migration, odontogenic differentiation, mineralized nodule formation, and immunomodulatory properties of hDPSCs.

METHODS

To address the melatonin biological effects on hDPSCs, the cytocompatibility, proliferation, cell migration, odontogenic differentiation, mineralized nodule formation, and immunomodulatory properties of hDPSCs after melatonin treatment were evaluated. The statistical differences were evaluated using 1-way analysis of variance with the Tukey multiple comparison test.

RESULTS

We found that melatonin did not alter hDPSC immunophenotype or cell viability, even at the highest concentrations used. However, using intermediate melatonin concentrations (10-300 μmol/L), a significantly higher proliferation rate (P < .05 and P < .01) and migration of hDPSCs (P < .01) were observed. Importantly, melatonin treatment (100 μmol/L) significantly increased the secretion of the anti-inflammatory cytokine transforming growth factor beta (P < .05 and P < .01) and provoked a more robust antiproliferative effect on mitogen-stimulated T cells (P < .05). Finally, and unlike previous results found with mesenchymal stem cells from other sources, melatonin fails to induce or accelerate the spontaneous osteogenic differentiation of hDPSCs.

CONCLUSIONS

Together, these findings provide key data on the bioactivity of melatonin and its effects on hPDSC biological and immunomodulatory properties.

Salivary Gland Dysfunction in Stroke Patients Is Associated with Increased Protein Glycoxidation and Nitrosative Stress

Stroke is one of the leading causes of disability and death worldwide. Despite intensive medical care, many of the complaints directly threatening the patient's life marginalize their dental needs after the stroke. Recent studies indicate reduced saliva secretion in stroke patients in addition to the increased incidence of caries and periodontal disease. Since oxidative stress plays a vital role in the pathogenesis of salivary gland hypofunction and neurodegenerative disorders (including stroke), this is the first to evaluate the relationship between salivary gland activity and protein glycoxidation and nitrosative damage. The content of glycation and protein oxidation products and nitrosative stress was assessed in nonstimulated (NWS) and stimulated (SWS) whole saliva of stroke patients with normal salivary secretion and hyposalivation (reduced saliva production). The study included 30 patients in the stroke's subacute phase and 30 healthy controls matched by age and sex. We have shown that stroke patients with hyposalivation show increased contents of protein glycation (↑Amadori products and ↑advanced glycation end products), glycoxidation (↑dityrosine), and nitration (↑nitrotyrosine) products compared to stroke cases with normal salivary secretion and control group. Interestingly, higher oxidative/nitrosative stress was found in NWS, which strongly correlates with salivary flow rate, total protein content, and salivary amylase activity. Such relationships were not observed in the control group. Summarizing, oxidative and nitrosative stress may be one of the mechanisms responsible for the impairment of saliva secretion in stroke patients. However, extraglandular sources of salivary oxidative stress in stroke patients cannot be excluded. Further studies to assess salivary gland hypofunction in stroke cases are necessary.

Melatonin is an effective protector of gingival cells damaged by the cytotoxic effect of glutamate and DL-buthionine sulfoximine

BACKGROUND AND OBJECTIVE

Cellular damage related to oxidative stress (OS) is implicated in periodontal diseases (PD). Melatonin (MEL) has multiple functions, and it has been described as a potential treatment for PD. We aim at evaluating the protective effects of MEL on an in vitro model of cellular damage triggered by glutamate (GLUT) and DL-buthionine sulfoximine (BSO), on gingival cells (GCs) in culture.

MATERIAL AND METHODS

A primary culture of GCs from Wistar rats was developed in order to test the protective property of MEL; BSO and GLUT were administered alone as well as in combination with MEL. The viability and apoptosis were measured with MTT assay and TUNEL, respectively, and the concentration of superoxide anion ( O 2 - ) was measured with the NBT method.

RESULTS

The combination of BSO and GLUT treatment resulted in a decreased viability of GCs. This was evidenced by the increase in both the production of superoxide anion and apoptosis. After MEL administration, the oxidant and pro-apoptotic effects of BSO and GLUT were totally counteracted.

CONCLUSIONS

These findings demonstrated that MEL has an effective protective role on GCs subjected to cellular damage in a model of OS and cytotoxicity triggered by BSO and GLUT. Consequently, MEL could be used as a therapeutic agent in PD which begin with a significative loss of GCs.

The effect of melatonin on prevention of bisphosphonate-related osteonecrosis of the jaw: an animal study in rats

Objectives

Melatonin induces human stem cells, converts pre-osteoblasts to mature osteoblasts, and reduces the duration of this transition. However, melatonin itself prevents activation of osteoclasts. Here, we evaluate the role of melatonin in prevention of bisphosphonate-related osteonecrosis of the jaw.

Materials and Methods

In this experimental-interventional study, 30 rats were evaluated in 3 groups. The first and second groups received saline and zoledronic acid, respectively, for 4 weeks and the third group received 4 weeks of zoledronic acid and 3 weeks of melatonin simultaneously. First-right-maxillary-molar extraction was performed for all animals, which were sacrificed after 4 weeks of recovery. The extraction sockets were examined histologically for the presence of osteonecrosis, number of osteoclasts and fibroblasts, severity of inflammation, and vascularization. Data were analyzed by chi-square, one-way ANOVA, Tukey, Kruskal–Wallis and Fisher’s exact statistical tests (α=0.05).

Results

Osteonecrosis was observed in 20%, 90%, and 70% of the first, second and third groups, respectively (P=0.008). The lowest number of osteoclasts and fibroblasts was seen in the third group.

Conclusion

Melatonin may effectively prevent some undesirable side effects of bisphosphonates. However, further studies are required to confirm the results of this study.

Melatonin and gastrointestinal cancers: Current evidence based on underlying signaling pathways

Gastrointestinal (GI) cancers, leading causes of cancer-related deaths, have been serious challenging human diseases up to now. Because of high rates of mortality, late-stage diagnosis, metastasis to distant locations, and low effectiveness and adverse events of routine standard therapies, the quality of life and survival time are low in patients with GI cancers. Hence, many efforts need to be done to explore and find novel efficient treatments. Beneficial effects of melatonin have been reported in a wide variety of human diseases. Melatonin has antioxidant, anti-inflammatory, antimicrobial, and anticancer effects. Various studies have showed the regulatory effects of melatonin on apoptotsis, autophagy and angiogenesis; these properties result in the inhibition of invasion, migration, and proliferation of GI cancer cells in vivo and in vitro. Together, this review suggests that melatonin in combination with anticancer agents may improve the efficacy of routine medicine and survival rate of patients with cancer.

Effect of melatonin versus injectable platelet rich fibrin on critical wound healing in submandibular salivary glands of diabetic rats

Background

Diabetes mellitus (DM) has harmful effects on body organs, including submandibular salivary glands (SMGs). It impairs wound healing process that follow sialoadenectomy. Yet there is no complete cure to diabetes, the available medications tend to control the side effects of DM or manage insulin resistance. Herein we tried to investigate the possible effects of injectable platelet rich fibrin (i-PRF) and melatonin on wound healing in diabetic rats.

Material and methods

Surgical defects were created in SMGs of 30 rats after confirmation of DM induction. Then rats were randomly and equally allocated into three groups. Group I served as control group; group II received topically applied i-PRF, and group III received topically administrated melatonin. After 28 days all rats were euthanized, and SMGs were processed for histological and biochemical analysis.

Results

Both i-PRF and melatonin caused significant reduction of malondialdehyde (P < 0.0001) and caspase-3 (P < 0.001) and significant increase in vascular endothelial growth factors (P = 0.001,0.009 respectively) that increased SMGs regenerative capacity when compared to diabetic group. Melatonin showed superior results regarding the histomorphological structure of SMGs.

Conclusion

Melatonin and i-PRF can be possible candidates for improvement of wound healing events in SMGs of diabetic rats.

Melatonin antagonizes lipopolysaccharide-induced pulpal fibroblast responses

Background

Pulpal inflammation is known to be mediated by multiple signaling pathways. However, whether melatonin plays regulatory roles in pulpal inflammation remains unclear. This study aimed at elucidating an in situ expression of melatonin and its receptors in human pulpal tissues, and the contribution of melatonin on the antagonism of lipopolysaccharide (LPS)-infected pulpal fibroblasts.

Methods

Melatonin expression in pulpal tissues harvested from healthy teeth was investigated by immunohistochemical staining. Its receptors, melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2), were also immunostained in pulpal tissues isolated from healthy teeth and inflamed teeth diagnosed with irreversible pulpitis. Morphometric analysis was subsequently performed. After LPS infection of cultured pulpal fibroblasts, cyclo-oxygenase (COX) and interleukin-1 β (IL-1 β) transcripts were examined by using reverse transcription-polymerase chain reaction (RT-PCR). Analysis of mRNA expression was performed to investigate an antagonism of LPS stimulation by melatonin via COX and IL-1 β induction. Mann-Whitney U test and One-way ANOVA were used for statistical analysis to determine a significance level.

Results

Melatonin was expressed in healthy pulpal tissue within the odontoblastic zone, cell-rich zone, and in the pulpal connective tissue. Furthermore, in health, strong MT1 and MT2 expression was distributed similarly in all 3 pulpal zones. In contrast, during disease, expression of MT2 was reduced in inflamed pulpal tissues (P-value< 0.001), but not MT1 (P-value = 0.559). Co-culturing of melatonin with LPS resulted in the reduction of COX-2 and IL-1 β expression in primary pulpal fibroblasts, indicating that melatonin may play an antagonistic role to LPS infection in pulpal fibroblasts.

Conclusions

Human dental pulp abundantly expressed melatonin and its receptors MT1 and MT2 in the odontoblastic layers and pulpal connective tissue layers. Melatonin exerted antagonistic activity against LPS-mediated COX-2 and IL-1 β induction in pulpal fibroblasts, suggesting its therapeutic potential for pulpal inflammation and a possible role of pulpal melatonin in an immunomodulation via functional melatonin receptors expressed in dental pulp.

Melatonin as an Agent for Direct Pulp-Capping Treatment

Melatonin plays an essential role in the regulation of bone growth. The actions that melatonin exerts on odontoblasts may be similar to its action on osteoblasts. This research aimed to evaluate the pulp response to melatonin used for direct pulp capping to evaluate the antioxidant effect of melatonin administered orally and its influence on dental pulp. Direct pulp capping was performed on the upper molars of Sprague Dawley rats using melatonin or Mineral Trioxide Aggregate (MTA). The study groups were: MTA; Melatonin; MTA + Melatonin administered orally; and Melatonin + Melatonin administered orally. In the latter two groups, the animals drank water dosed with melatonin ad libitum (10 mg/100 mL). After 30 days, the animals were sacrificed, and 5 ml of blood, the kidneys, and the liver were extracted in order to evaluate oxidative stress using thiobarbituric acid reactive substances testing (TBARS). Fragments of the maxilla containing the study molars were prepared for histological evaluation. The degree of pulp inflammation and pulp necrosis, the presence of reparative dentin and dentin bridging the pulp chamber, the presence and regularity of the odontoblastic layer, and the presence of pulp fibrosis were evaluated. No significant differences were found between the four study groups for any of the studied histological variables. The oral administration of melatonin did not modify the local effects of MTA or melatonin on dental pulp, or reduce basal-level oxidative stress. The effect of melatonin on pulp is similar to that of MTA and may be used as an agent for direct pulp capping.

Potential of Melatonin as Adjuvant Therapy of Oral Cancer in the Era of Epigenomics

The wide variety of epigenetic controls available is rapidly expanding the knowledge of molecular biology even overflowing it. At the same time, it can illuminate unsuspected ways of understanding the etiology of cancer. New emerging therapeutic horizons, then, promise to overcome the current antitumor strategies need. The translational utility of this complexity is particularly welcome in oral cancer (OC), in which natural history is alarmingly disappointing due to the invasive and mutilating surgery, the high relapsing rate, the poor quality of life and the reduced survival after diagnosis. Melatonin activates protective receptor-dependent and receptor-independent processes that prevent tissue cancerisation and inhibit progressive tumor malignancy and metastasis. Related evidence has shown that melatonin pleiotropy encompasses gene expression regulation through all the three best-characterized epigenetic mechanisms: DNA methylation, chromatin modification, and non-coding RNA. OC has received less attention than other cancers despite prognosis is usually negative and there are no significant therapy improvements recorded in the past decade. However, a large research effort is being carried out to elucidate how melatonin´s machinery can prevent epigenetic insults that lead to cancer. In the light of recent findings, a comprehensive examination of biochemistry through which melatonin may reverse epigenetic aberrations in OC is an extraordinary opportunity to take a step forward in the clinical management of patients.

Transmucosal delivery of melatonin-encapsulated niosomes in a mucoadhesive gel

AIM

A transmucosal niosome gel was developed to improve the pharmacokinetics of exogenous melatonin.

MATERIALS & METHODS

The melatonin niosomes (MN) gel was characterized and melatonin levels were determined in healthy volunteers.

RESULTS

Micron-sized MN in a gel, mean ex vivo residence time of more than 3 h with maximum adhesiveness at 25 and 37°C showed similar in vitro release but different in vitro permeation to melatonin gel. Oral transmucosal MN gels, at 2.5, 5 and 10 mg, topically applied in 14 healthy volunteers in a randomized double-blinded crossover design with 7-day washout, gave dose-proportional pharmacokinetics, with improved absorption and prolonged systemic circulation.

CONCLUSION

The transmucosal MN gel provides a topical option for melatonin administration with substantial prolonged systemic delivery.

Melatonin release by exocytosis in the rat parotid gland

Several beneficial effects on oral health are ascribed to melatonin. Due to its lipophilic nature, non-protein-bound circulating melatonin is usually thought to enter the saliva by passive diffusion through salivary acinar gland cells. Recently, however, using transmission electron microscopy (TEM), melatonin was found in acinar secretory granules of human salivary glands. To test the hypothesis that granular located melatonin is actively discharged into the saliva by exocytosis, i.e. contrary to the general belief, the β-adrenergic receptor agonist isoprenaline, which causes the degranulation of acinar parotid serous cells, was administered to anaesthetised rats. Sixty minutes after an intravenous bolus injection of isoprenaline (5 mg kg-1 ), the right parotid gland was removed; pre-administration, the left control gland had been removed. Samples were processed to demonstrate melatonin reactivity using the immunogold staining method. Morphometric assessment was made using TEM. Gold particles labelling melatonin appeared to be preferentially associated with secretory granules, occurring in their matrix and at membrane level but, notably, it was also associated with vesicles, mitochondria and nuclei. Twenty-six per cent of the total granular population (per 100 μm2 per cell area) displayed melatonin labelling in the matrix; three-quarters of this fraction disappeared (P < 0.01) in response to isoprenaline, and melatonin reactivity appeared in dilated lumina. Thus, evidence is provided of an alternative route for melatonin to reach the gland lumen and the oral cavity by active release through exocytosis, a process which is under the influence of parasympathetic and sympathetic nervous activity and is the final event along the so-called regulated secretory pathway. During its stay in granules, anti-oxidant melatonin may protect their protein/peptide constituents from damage.

Effect of Red Wine Intake on Serum and Salivary Melatonin Levels: A Randomized, Placebo-Controlled Clinical Trial

Melatonin (MLT) is a recently discovered phytochemical in wine, but its influence on physiological MLT levels is still unknown. This study aimed at evaluating variations, in serum and saliva, of MLT concentrations after the intake of MLT-enriched red wine. Twelve healthy volunteers were recruited to receive 125 mL of red wine naturally lacking of MLT (placebo, PLC), or the same wine enriched with MLT (MLT+). A physiological steady decline of serum MLT was observed from baseline up to 90 min, for both wines. After PLC intake, the decrease was significantly faster than the one occurring after MLT+ wine, which thus delayed the drop down of serum MLT with a plateau at 30⁻60 min. Salivary MLT levels slightly peaked at 45 min after MLT+ wine intake, without statistical significance. Therefore, the intake of a glass of MLT-enriched red wine changed serum levels of the indoleamine, supporting the role of wine MLT in counteracting the physiological decline of the hormone into the bloodstream.

Research progress on the role of melatonin and its receptors in animal reproduction: A comprehensive review

Melatonin and its receptors play a crucial role in the regulation of the animal reproductive process, primarily in follicular development. However, the role that melatonin performs in regulating hormones related with reproduction remains unclear. Melatonin and its receptors are present both in female and male animals' organs, such as ovaries, heart, brain and liver. Melatonin regulates ovarian actions and is a key mediator of reproductive actions. Melatonin has numerous effects on animal reproduction, such as protection of gametes and embryos, response to clock genes, immune-neuroendocrine, reconciliation of seasonal variations in immune function, and silence or blockage of genes. The growth ratio of reproductive illnesses in animals has raised a remarkable concern for the government, animal caretakers and farm managers. In order to resolve this challenging issue, it is very necessary to conduct state-of-the-art research on melatonin and its receptors because melatonin has considerable physiognomies. This review article presents a current contemporary research conducted by numerous researchers from the entire world on the role of melatonin and its receptors in animal reproduction, from the year 1985 to the year 2017. Furthermore, this review shows scientific research challenges related to melatonin receptors and their explanations based on the findings of 172 numerous research articles, and also represents significant proficiencies of melatonin in order to show enthusiastic study direction for animal reproduction researchers.

Prophylactic supplement with melatonin successfully suppresses the pathogenesis of periodontitis through normalizing RANKL/OPG ratio and depressing the TLR4/MyD88 signaling pathway

Periodontitis (PD) is an inflammatory disease characterized by gingival inflammation and resorption of alveolar bone. Impaired receptor activator of nuclear factor-kappa B ligand/osteoprotegerin (RANKL/OPG) signaling caused by enhanced production of pro-inflammatory cytokines plays an essential role in the pathogenesis of PD. Considering melatonin possesses significant anti-inflammatory property, this study aimed to determine whether prophylactic treatment with melatonin would effectively normalize RANKL/OPG signaling, depress toll-like receptor 4/myeloid differentiation factor 88 (TLR4/MyD88)-mediated pro-inflammatory cytokine activation, and successfully suppress the pathogenesis of PD. PD was induced in adult rats by placing the ligature at molar subgingival regions. Fourteen days before PD induction, 10, 50, or 100 mg/kg of melatonin was intraperitoneally injected for consecutive 28 days. Biochemical and enzyme-linked immunosorbent assay were used to detect TLR4/MyD88 activity, RANKL, OPG, interleukin 1β, interleukin 6, and tumor necrosis factor-α levels, respectively. The extent of bone loss, bone mineral intensity, and calcium intensity was further evaluated by scanning electron microscopy, micro-computed tomography, and energy-dispersive X-ray spectroscopy. Results indicated that high RANKL/OPG ratio, TLR4/MyD88 activity, and pro-inflammatory cytokine levels were detected following PD. Impaired biochemical findings paralleled well with severe bone loss and reduced calcium intensity. However, in rats pretreated with melatonin, all above parameters were successfully returned to nearly normal levels with maximal change observed in rats receiving 100 mg/kg. As prophylactic treatment with melatonin effectively normalizes RANKL/OPG signaling by depressing TLR4/MyD88-mediated pro-inflammatory cytokine production, dietary supplement with melatonin may serve as an advanced strategy to strengthen oral health to counteract PD-induced destructive damage.

Melatonin exerts anti-oral cancer effect via suppressing LSD1 in patient-derived tumor xenograft models

Aberrant activation of histone lysine-specific demethylase (LSD1) increases tumorigenicity; hence, LSD1 is considered a therapeutic target for various human cancers. Although melatonin, an endogenously produced molecule, may defend against various cancers, the precise mechanism involved in its anti-oral cancer effect remains unclear. Patient-derived tumor xenograft (PDTX) models are preclinical models that can more accurately reflect human tumor biology compared with cell line xenograft models. Here, we evaluated the anticancer activity of melatonin by using LSD1-overexpressing oral cancer PDTX models. By assessing oral squamous cell carcinoma (OSCC) tissue arrays through immunohistochemistry, we examined whether aberrant LSD1 overexpression in OSCC is associated with poor prognosis. We also evaluated the action mechanism of melatonin against OSCC with lymphatic metastases by using the PDTX models. Our results indicated that melatonin, at pharmacological concentrations, significantly suppresses cell proliferation in a dose- and time-dependent manner. The observed suppression of proliferation was accompanied by the melatonin-mediated inhibition of LSD1 in oral cancer PDTXs and oral cancer cell lines. In conclusion, we determined that the beneficial effects of melatonin in reducing oral cancer cell proliferation are associated with reduced LSD1 expression in vivo and in vitro.

Antioxidant effects of melatonin in heart tissue after induction of experimental periodontitis in rats

The aim of this study was to evaluate the effects of melatonin on the oxidative stress in heart tissues after induction of experimental periodontitis in rats. Thirty Wistar Albino male rats were divided into four groups as follows: healthy + saline solution (Hs, n = 7), healthy + melatonin (Hm, n = 7), periodontitis + saline solution (Ps, n = 8), and periodontitis + melatonin (Pm, n = 8). Experimental periodontitis was induced using a ligature placed at the gingival margin of the maxillary second molars. Melatonin was applied intraperitoneally (10 mg/kg) every day for 2 weeks. After sacrificing the rats, serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) levels, and melatonin levels were evaluated. The Pm group exhibited lower alveolar bone loss than the Ps group. Melatonin levels increased in the periodontitis groups, and the Pm group had lower MDA levels and higher GSH-Px levels than the Ps group. These findings suggest that melatonin administration reduces MDA and increases GSH-Px levels in heart tissue, and these effects may be due to its antioxidant properties. Further studies are needed to understand the effects of melatonin on the association between periodontitis and cardiovascular disease.

Topical Delivery of Coumestrol from Lipid Nanoemulsions Thickened with Hydroxyethylcellulose for Antiherpes Treatment

We have recently shown that coumestrol, an isoflavonoid-like compound naturally occurring in soybeans, alfafa, and red clover, inhibited Herpes Simplex Virus types 1 (HSV-1) and 2 (HSV-2) replication. In this study, we designed coumestrol formulations in an attempt to enable its topical delivery to mucosa tissues. Physicochemical and microscopic examinations suggested that coumestrol was efficiently incorporated in positively-charged nanoemulsions dispersed in a hydroxyethylcellulose gel. The higher coumestrol flux through excised porcine esophageal mucosa was detected from nanoemulsions composed by a fluid phospholipid (dioleylphosphocholine, DOPC) in comparison with that of a rigid one (distearoylphosphocholine, DSPC) in two mucosa conditions (intact and injured). Such results were supported by confocal fluorescence images. Furthermore, the low IC₅₀ values demonstrated an increasement in the antiviral inhibition against HSV-1 and HSV-2 after incorporation of coumestrol into nanoemulsions containing DOPC. Overall, coumestrol-loaded nanoemulsions proved to be beneficial for herpes simplex treatment.

Diabetic Status Influences the Storage of Melatonin in Human Salivary Glands

Recently we reported on the detailed localization of melatonin (and its receptors) in human salivary glands, revealing that serous cells are able to store and secrete melatonin into saliva. Since we found that type 2 diabetic patients display reduced melatonin content in saliva, our next step was to examine the presence of melatonin in salivary glands removed from type 2 diabetic subjects. The resulting data were compared with those previously obtained by identical procedures in non-diabetics, to establish if the diabetic status may affect melatonin distribution. Bioptic samples of diabetic parotid and submandibular glands were fixed, dehydrated, embedded in Epon Resin and processed to demonstrate melatonin reactivity by the immunogold staining method. The labeling density (expressed as the number of gold particles per μm² /granule) and the percentage of melatonin-positive granules were assessed in diabetic samples. These values were compared with those in non-diabetic samples and differences were evaluated. In parotid and submandibular diabetic glands the reactivity for melatonin was specifically associated with secretory granules and small vesicles in serous cells. Melatonin reactivity was higher in parotid than in submandibular glands. Our data were in line with those obtained in our previous study on non-diabetic glands. Diabetic salivary glands showed a higher labeling density and a lower number of melatonin-positive granules compared to non-diabetic glands. Taken together, these data might explain the decreased salivary melatonin content and the associated oral problems observed in diabetics. Anat Rec, 301:711-716, 2018. © 2017 Wiley Periodicals, Inc.

Melatonin inhibits TPA-induced oral cancer cell migration by suppressing matrix metalloproteinase-9 activation through the histone acetylation

Melatonin exerts antimetastatic effects on liver and breast cancer and also inhibits matrix metalloproteinase (MMP) activity. However, the detailed impacts and underlying mechanisms of melatonin on oral cancer cell metastasis are still unclear. This study showed that melatonin attenuated the 12-O-tetradecanoylphorbol-13-acetate-induced migration of oral cancer cell lines, HSC-3 and OECM-1. Zymography, quantitative real-time PCR, and Western blotting analyses revealed that melatonin lessened MMP-9 enzyme activity as well as the expression of MMP-9 mRNA and protein. Furthermore, melatonin suppressed the phosphorylation of the ERK1/2 signalling pathway, which dampened MMP-9 gene transcription by affecting the expression of transcriptional coactivators, such as CREB-binding protein (CREBBP) and E1A binding protein p300 (EP300), and decreasing histone acetylation in HSC-3 and OECM-1 cells. Examinations on clinical samples exhibited that MMP-9, CREBBP, and EP300 were significantly increased in oral cancer tissues. Moreover, the relative level of CREBBP was positively correlated with the expression of MMP-9 and EP300. In conclusion, we demonstrated that melatonin inhibits the motility of HSC-3 and OECM-1 cells in vitro through a molecular mechanism that involves attenuation of MMP-9 expression and activity mediated by decreased histone acetylation.

Melatonin as a potential inhibitory agent in head and neck cancer

Melatonin is a molecule secreted by the pineal gland; it is an important regulator of sleep and circadian rhythms. Through multiple interrelated mechanisms, melatonin exhibits various inhibitory properties at different stages of tumor progression. Many studies have explored the oncostatic effects of melatonin on hormone-dependent tumors. In this review, we highlight recent advances in understanding the effects of melatonin on the development of head and neck cancers, including molecular mechanisms identified through experimental and clinical observations. Because melatonin exerts a wide range of effects, melatonin may influence many mechanisms that influence the development of cancer. These include cell proliferation, apoptosis, angiogenesis, extracellular matrix remodeling through matrix metalloproteinases, and genetic polymorphism. Thus, the evidence discussed in this article will serve as a basis for basic and clinical research to promote the use of melatonin for understanding and controlling the development of head and neck cancers.

Oral Mucositis: Melatonin Gel an Effective New Treatment

The current treatment for cervico-facial cancer involves radio and/or chemotherapy. Unfortunately, cancer therapies can lead to local and systemic complications such as mucositis, which is the most common dose-dependent complication in the oral cavity and gastrointestinal tract. Mucositis can cause a considerably reduced quality of life in cancer patients already suffering from physical and psychological exhaustion. However, the role of melatonin in the treatment of mucositis has recently been investigated, and offers an effective alternative therapy in the prevention and/or management of radio and/or chemotherapy-induced mucositis. This review focuses on the pathobiology and management of mucositis in order to improve the quality of cancer patients' lives.

Effect of electromagnetic fields and antioxidants on the trace element content of rat teeth

The purpose of this study was to examine the possible effect of extremely low-frequency electromagnetic fields (ELF-EMFs), from a high-voltage source, on rat teeth in terms of changes in trace elements (TEs) and the effect of antioxidants (melatonin [MLT] and Ganoderma lucidum [GL]) in counteracting these effects. We used adult male Wistar albino rats with a mean weight of 250–300 g and divided the rats into eight groups. The groups were subjected to an ELF-EMF that was applied with a high-voltage line for 8 hours/day for 26 days (Groups I, II, and III) or 52 days (Groups V, VI, and VII). Groups IV and VIII were the 26- and 52-day control/sham groups, respectively. Groups II and VI were treated with GL, and Groups III and VII were treated with MLT. MLT and GL were administered daily based on the weight of the animals and appropriate standards. At the end of the study, the rats were euthanized, and their anterior teeth were extracted. The teeth were preserved in pure water before evaluating the major TEs. At the end of the study, TE concentrations (in mg/kg) were assessed in the control and test groups. Compared with Group V, statistically significant differences in the concentrations of zinc (Zn) and strontium (Sr) were found for Group VII (ELF-EMF + MLT) (P<0.05). Therefore, ELF-EMF exposure can change the content of certain TEs in teeth and, after administering MLT and GL, the values of some of the TEs return to normal.

Melatonin antagonizes interleukin-18-mediated inhibition on neural stem cell proliferation and differentiation

Neural stem cells (NSCs) are self‐renewing, pluripotent and undifferentiated cells which have the potential to differentiate into neurons, oligodendrocytes and astrocytes. NSC therapy for tissue regeneration, thus, gains popularity. However, the low survivals rate of the transplanted cell impedes its utilities. In this study, we tested whether melatonin, a potent antioxidant, could promote the NSC proliferation and neuronal differentiation, especially, in the presence of the pro‐inflammatory cytokine interleukin‐18 (IL‐18). Our results showed that melatonin per se indeed exhibited beneficial effects on NSCs and IL‐18 inhibited NSC proliferation, neurosphere formation and their differentiation into neurons. All inhibitory effects of IL‐18 on NSCs were significantly reduced by melatonin treatment. Moreover, melatonin application increased the production of both brain‐derived and glial cell‐derived neurotrophic factors (BDNF, GDNF) in IL‐18‐stimulated NSCs. It was observed that inhibition of BDNF or GDNF hindered the protective effects of melatonin on NSCs. A potentially protective mechanism of melatonin on the inhibition of NSC's differentiation caused IL‐18 may attribute to the up‐regulation of these two major neurotrophic factors, BNDF and GNDF. The findings indicate that melatonin may play an important role promoting the survival of NSCs in neuroinflammatory diseases.

Melatonin Receptor Agonists as the "Perioceutics" Agents for Periodontal Disease through Modulation of Porphyromonas gingivalis Virulence and Inflammatory Response

Aim

“Perioceutics” including antimicrobial therapy and host modulatory therapy has emerged as a vital adjunctive treatment of periodontal disease. Melatonin level was significantly reduced in patients with periodontal diseases suggesting melatonin could be applied as a potential “perioceutics” treatment of periodontal diseases. This study aims to investigate the effects of melatonin receptor agonists (melatonin and ramelteon) on Porphyromonas gingivalis virulence and Porphyromonas gingivalis-derived lipopolysaccharide (Pg-LPS)-induced inflammation.

Methods

Effects of melatonin receptor agonists on Porphyromonas gingivalis planktonic cultures were determined by microplate dilution assays. Formation, reduction, and viability of Porphyromonas gingivalis biofilms were detected by crystal violet staining and MTT assays, respectively. Meanwhile, biofilms formation was also observed by confocal laser scanning microscopy (CLSM). The effects on gingipains and hemolytic activities of Porphyromonas gingivalis were evaluated using chromogenic peptides and sheep erythrocytes. The mRNA expression of virulence and iron/heme utilization was assessed using RT-PCR. In addition, cell viability of melatonin receptor agonists on human gingival fibroblasts (HGFs) was evaluated by MTT assays. After pretreatment of melatonin receptor agonists, HGFs were stimulated with Pg-LPS and then release of cytokines (IL-6 and lL-8) was measured by enzyme-linked immunosorbent assay (ELISA).

Results

Melatonin and ramelteon did exhibit antimicrobial effects against planktonic culture. Importantly, they inhibited biofilm formation, reduced the established biofilms, and decreased biofilm viability of Porphyromonas gingivalis. Furthermore, they at sub-minimum inhibitory concentration (sub-MIC) concentrations markedly inhibited the proteinase activities of gingipains and hemolysis in a dose-dependent manner. They at sub-MIC concentrations significantly inhibited the mRNA expression of virulence factors (kgp, rgpA, rgpB, hagA, and ragA), while increasing the mRNA expression of ferritin (ftn) or hemolysin (hem). They did not show obvious cytotoxicity toward HGFs. They inhibited Pg-LPS-induced IL-6 and IL-8 secretion, which was reversed by luzindole, the melatonin receptor antagonist.

Conclusion

Melatonin receptor agonists can inhibit planktonic and biofilm growth of Porphyromonas gingivalis by affecting the virulent properties, as well as Pg-LPS-induced inflammatory response. Our study provides new evidence that melatonin receptor agonists might be useful as novel “perioceutics” agents to prevent and treat Porphyromonas gingivalis-associated periodontal diseases.

The Role of Nutrition in Periodontal Health: An Update

Periodontal health is influenced by a number of factors such as oral hygiene, genetic and epigenetic factors, systemic health, and nutrition. Many studies have observed that a balanced diet has an essential role in maintaining periodontal health. Additionally, the influences of nutritional supplements and dietary components have been known to affect healing after periodontal surgery. Studies have attempted to find a correlation between tooth loss, periodontal health, and nutrition. Moreover, bone formation and periodontal regeneration are also affected by numerous vitamins, minerals, and trace elements. The aim of this review is to critically appraise the currently available data on diet and maintenance of periodontal health and periodontal healing. The effects of nutritional intervention studies to improve the quality of life and well-being of patients with periodontal disease have been discussed.

Therapeutic potential of melatonin in oral medicine and periodontology

Melatonin (N-acetyl-5-methoxy tryptamine) is a substance secreted by multiple organs in vertebrates. In addition to playing a part in the circadian cycle of the body, melatonin is known to have antioxidant, antiinflammatory, and antioncotic effects on human tissues. Oral cavity is affected by a number of conditions such as periodontitis, mucositis, cancers, and cytotoxicity from various drugs or biomaterials. Research has suggested that melatonin is effective in treating the aforementioned pathologies. Furthermore, melatonin has been observed to enhance osseointegration and bone regeneration. The aim of this review is to critically analyze and summarize the research focusing on the potential of melatonin in the field of oral medicine. Topical administration of melatonin has a positive effect on periodontal health and osseointegration. Furthermore, melatonin is particularly effective in improving the periodontal parameters of diabetic patients with periodontitis. Melatonin exerts a regenerative effect on periodontal bone and may be incorporated into of periodontal scaffolds. The cytotoxic effect of various drugs and dental materials may be countered by the antioxidant properties of melatonin. Topical administration of melatonin promotes the healing of tooth extraction sockets and may also impede the progression of oral cancer. Although, there are a number of current and potential applications of melatonin, further long term clinical and animal studies are needed to assess its efficacy. Moreover, the role of melatonin supplements in the management of periodontitis should also be assessed.

Malondialdehyde, superoxide dismutase and melatonin levels in gingival crevicular fluid of aggressive and chronic periodontitis patients

BACKGROUND

The aim of this study was to investigate malondialdehyde (MDA), superoxide dismutase (SOD) and melatonin levels in the gingival crevicular fluid (GCF) of patients with chronic periodontitis (CP) and generalized aggressive periodontitis (GAgP) as biomarkers for oxidative stress.

METHODS

The study comprised 65 subjects: 15 healthy individuals, 25 CP patients and 25 GAgP patients. Plaque index, gingival index, pocket depth, clinical attachment level measurements and GCF samples were obtained from all subjects. MDA, SOD and melatonin levels were determined utilizing enzyme-linked immunosorbent assay.

RESULTS

GCF-MDA levels were significantly higher in the GAgP group compared to the CP and control groups (p < 0.001) and significantly higher in the CP group than the C group (p < 0.001). SOD and melatonin GCF levels were significantly higher in the control than the GAgP and CP groups (p < 0.05), and significantly lower in the GAgP than the CP group (p < 0.05). The CP group demonstrated a significant negative correlation between GCF-MDA and melatonin concentrations. A positive correlation was observed between SOD and CAL in the CP group and PD in the GAgP group.

CONCLUSIONS

MDA, melatonin and SOD could be considered as biomarkers for oxidative stress in periodontal diseases and might be useful diagnostic aids in distinguishing CP and GAgP patients.

Evaluation of melatonin levels in saliva in gingivitis and periodontitis cases: A pilot study

Objective:

To evaluate the melatonin levels in saliva in gingivitis and periodontitis cases.

Background:

Melatonin has strong antioxidant, free radical scavenging, and immunomodulating properties, acts on osteoblasts directly to stimulate cell proliferation and synthesis of Type I collagen, and promotes bone formation.

Materials and Methods:

A total of thirty participants were selected and divided into three groups (control group, gingivitis group, and periodontitis group). In each group, ten participants were taken. Salivary melatonin was estimated in each of the three groups.

Results:

Results from this study showed that the mean levels of salivary melatonin increased as severity increased from control to periodontitis, i.e., the mean levels were highest in periodontitis followed by gingivitis and least in control group. The melatonin level of all participants was positively and significantly (P < 0.01) correlated with their gingival index (r = 0.85, P < 0.01) and probing depth (r = 0.72, P < 0.01).

Conclusion:

Salivary melatonin level varied with the severity of gingivitis and periodontitis. With increased severity of periodontal disease, the level of salivary melatonin also increased suggesting that salivary melatonin may act as a diagnostic biomarker for periodontal diseases.

Melatonin localization in human salivary glands

BACKGROUND

Circulating melatonin is believed to reach body fluids by crossing passively the cell membranes, but alternative ways for melatonin transport also are hypothesized. This investigation was carried out to furnish ultrastructural evidences for melatonin transport by salivary gland cells in order to indicate plausible routes by which circulating melatonin can reach saliva.

METHODS

Bioptic samples of parotid, submandibular and labial glands were processed for the electron microscopy and treated to demonstrate melatonin reactivity by the immunogold staining method.

RESULTS AND CONCLUSIONS

The preferential sites of melatonin reactivity were the granules and vesicles of serous cells. Our results suggested that the acinar cells are able to store melatonin and that the hormone can be released into saliva through granule and vesicle exocytosis. The quantitative evaluation of labelling showed that the parotid gland is the most involved in the release of melatonin in saliva.