A new perspective in Oral health: potential importance and actions of melatonin receptors MT1, MT2, MT3, and RZR/ROR in the oral cavity

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: A look at protozoal and helminths

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

Influence of Different Light Spectra on Melatonin Synthesis by the Pineal Gland and Influence on the Immune System in Chickens

It is well known that the pineal gland in birds influences behavioural and physiological functions, including those of the immune system. The purpose of this research is to examine the endocrine-immune correlations between melatonin and immune system activity. Through a description of the immune-pineal axis, we formulated the objective to determine and describe: the development of the pineal gland; how light influences secretory activity; and how melatonin influences the activity of primary and secondary lymphoid organs. The pineal gland has the ability to turn light information into an endocrine signal suitable for the immune system via the membrane receptors Mel1a, Mel1b, and Mel1c, as well as the nuclear receptors RORα, RORβ, and RORγ. We can state the following findings: green monochromatic light (560 nm) increased serum melatonin levels and promoted a stronger humoral and cellular immune response by proliferating B and T lymphocytes; the combination of green and blue monochromatic light (560-480 nm) ameliorated the inflammatory response and protected lymphoid organs from oxidative stress; and red monochromatic light (660 nm) maintained the inflammatory response and promoted the growth of pathogenic bacteria. Melatonin can be considered a potent antioxidant and immunomodulator and is a critical element in the coordination between external light stimulation and the body's internal response.

Comparative evaluation of 1% melatonin gel in the treatment of intrabony defect: A randomized controlled clinical trial

BACKGROUND

The present study aims to evaluate and compare the efficacy of locally delivered 1% melatonin gel as an adjunct to non-surgical periodontal therapy (NSPT) in treatment of intrabony defect in Stage III periodontitis, clinically, and radiographically using cone-beam computed tomography (CBCT).

METHODS

This split-mouth clinical trial randomly allotted 44 bilateral intrabony defect (in 22 patients) into two groups where Group I was treated with NSPT with locally delivered placebo gel while Group II was treated with NSPT with 1% melatonin gel. The intrabony defect fill measured from cemento-enamel junction (CEJ)-base of the defect (BD), and the difference in the measurement values of CEJ-BD from baseline to 6 months denoting the bone fill and bone volume evaluated at 6 months using CBCT were the primary outcome measures. Secondary outcome measures were change in probing depth (PD), clinical attachment level (CAL), plaque index, and modified sulcus bleeding index recorded at baseline, 3 months, and 6 months.

RESULTS

Both the study groups showed improvements in assessed parameters, however, a significant gain in intrabony defect fill was observed in Group II (1.46 ± 0.58) as compared with Group I (0.50 ± 0.38) and change in bone volume for Group I was 21.4645 ± 8.8980 mm³ and for Group II was 51.8418 ± 30.2329 mm³ with P < 0.0001.The mean reduction in PD and gain in CAL was 3.90 ± 0.78 and 2.94 ± 0.80 in Group II and in Group I it was 3.23 ± 0.90 and 1.96 ± 0.80 (P < 0.0001).

CONCLUSION

The use of 1% melatonin gel as an adjunct to NSPT is more beneficial in achieving better clinical and radiographic outcome at 6 months which indicates that adjunct use of melatonin gel to NSPT as a local drug delivery is preferred when compared with NSPT and placebo gel alone.

Hormone and implant osseointegration: Elaboration of the relationship among function, preclinical, and clinical practice

As clusters of peptides or steroids capable of high-efficiency information transmission, hormones have been substantiated to coordinate metabolism, growth, development, and other physiological processes, especially in bone physiology and repair metabolism. In recent years, the application of hormones for implant osseointegration has become a research hotspot. Herein, we provide a comprehensive overview of the relevant reports on endogenous hormones and their corresponding supplementary preparations to explore the association between hormones and the prognosis of implants. We also discuss the effects and mechanisms of insulin, parathyroid hormone, melatonin, vitamin D, and growth hormone on osseointegration at the molecular and body levels to provide a foothold and guide future research on the systemic conditions that affect the implantation process and expand the relative contraindications of the implant, and the pre-and post-operative precautions. This review shows that systemic hormones can regulate the osseointegration of oral implants through endogenous or exogenous drug-delivery methods.

Oncostatic activities of melatonin: Roles in cell cycle, apoptosis, and autophagy

Melatonin, the major secretory product of the pineal gland, not only regulates circadian rhythms, mood, and sleep but also has actions in neoplastic processes which are being intensively investigated. Melatonin is a promising molecule which considered a differentiating agent in some cancer cells at both physiological and pharmacological concentrations. It can also reduce invasive and metastatic status through receptors MT1 and MT2 cytosolic binding sites, including calmodulin and quinone reductase II enzyme, and nuclear receptors related to orphan members of the superfamily RZR/ROR. Melatonin exerts oncostatic functions in numerous human malignancies. An increasing number of studies report that melatonin reduces the invasiveness of several human cancers such as prostate cancer, breast cancer, liver cancer, oral cancer, lung cancer, ovarian cancer, etc. Moreover, melatonin's oncostatic activities are exerted through different biological processes including antiproliferative actions, stimulation of anti-cancer immunity, modulation of the cell cycle, apoptosis, autophagy, the modulation of oncogene expression, and via antiangiogenic effects. This review focuses on the oncostatic activities of melatonin that targeted cell cycle control, with special attention to its modulatory effects on the key regulators of the cell cycle, apoptosis, and telomerase activity.

Usefulness of Melatonin and Other Compounds as Antioxidants and Epidrugs in the Treatment of Head and Neck Cancer

Along with genetic mutations, aberrant epigenetic alterations are the initiators of head and neck cancer carcinogenesis. Currently, several drugs are being developed to correct these epigenetic alterations, known as epidrugs. Some compounds with an antioxidant effect have been shown to be effective in preventing these malignant lesions and in minimizing the complications derived from cytotoxic treatment. Furthermore, in vitro and in vivo studies show a promising role in the treatment of head and neck squamous cell carcinoma (HNSCC). This is the case of supplements with DNA methylation inhibitory function (DNMTi), such as epigallocatechin gallate, sulforaphane, and folic acid; histone deacetylase inhibitors (HDACi), such as sodium butyrate and melatonin or histone acetyltransferase inhibitors (HATi), such as curcumin. The objective of this review is to describe the role of some antioxidants and their epigenetic mechanism of action, with special emphasis on melatonin and butyric acid given their organic production, in the prevention and treatment of HNSCC.

Effects of Antioxidant in Adjunct with Periodontal Therapy in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis

This review investigated whether the adjunctive use of antioxidants with periodontal therapy improves periodontal parameters in patients with type 2 diabetes. A systematic and extensive literature search for randomized controlled trials (RCTs) conducted before April 2021 was performed on the PubMed, Cochrane Library, and Web of Science databases. The risk of bias was assessed using the Cochrane risk-of-bias tool. A meta-analysis was performed to quantitatively evaluate the clinical outcomes following periodontal therapy. After independent screening of 137 initial records, nine records from eight RCTs were included. The risk-of-bias assessment revealed that all RCTs had methodological weaknesses regarding selective bias, although other risk factors for bias were not evident. This meta-analysis of two RCTs showed that periodontal pocket depths were significantly reduced in the groups treated with combined non-surgical periodontal therapy and melatonin than in those treated with non-surgical periodontal therapy alone. The present systematic review and meta-analysis suggest that the adjunctive use of melatonin, resveratrol, omega-3 fatty acids with cranberry juice, propolis, and aloe vera gel with periodontal therapy significantly improves periodontal disease parameters in patients with type 2 diabetes, and melatonin application combined with non-surgical periodontal therapy might significantly reduce periodontal pocket depth. However, there are still limited studies of melatonin in combination with non-surgical periodontal therapy in Type 2 diabetic patients, and more well-designed RCTs are required to be further investigated.

ROR: Nuclear Receptor for Melatonin or Not?

Whether the retinoic acid-related orphan receptor (ROR) is a nuclear receptor of melatonin remains controversial. ROR is inextricably linked to melatonin in terms of its expression, function, and mechanism of action. Additionally, studies have illustrated that melatonin functions analogous to ROR ligands, thereby modulating the transcriptional activity of ROR. However, studies supporting these interactions have since been withdrawn. Furthermore, recent crystallographic evidence does not support the view that ROR is a nuclear receptor of melatonin. Some other studies have proposed that melatonin indirectly regulates ROR activity rather than directly binding to ROR. This review aims to delve into the complex relationship of the ROR receptor with melatonin in terms of its structure, expression, function, and mechanism. Thus, we provide the latest evidence and views on direct binding as well as indirect regulation of ROR by melatonin, dissecting both viewpoints in-depth to provide a more comprehensive perspective on this issue.

Study on the Effects of Melatonin on Glycemic Control and Periodontal Parameters in Patients with Type II Diabetes Mellitus and Periodontal Disease

Background and Objectives: There is evidence that melatonin could improve the periodontal status and also glycemic control of patients with diabetes mellitus. Therefore, the aim of this study was to assess the effects of scaling and root planing plus adjunctive systemic treatment with melatonin on periodontal parameters and glycemic control in patients with type 2 diabetes and chronic periodontitis. Materials and Methods: The study was conducted on 54 subjects with periodontitis and diabetes mellitus randomly assigned to the study group (n = 27, subjects with scaling and root planing + melatonin) or control group (n = 27, subjects with scaling and root planing + placebo). Periodontal parameters (probing depth—PD; clinical attachment loss—CAL; bleeding on probing—BOP; and hygiene level) and glycated hemoglobin (HbA1c) were assessed at baseline and 8 weeks after. Results: At baseline, there were no significant differences between groups, but at the second evaluation 8 weeks later the association of melatonin with the non-surgical periodontal therapy exerted statistically significant improvements, both in periodontal parameters, with a significant decrease in periodontal disease severity, and glycated hemoglobin when compared to the control subjects. Conclusions: In our study, combined non-surgical periodontal treatment and systemic treatment with melatonin provided additional improvements to severe periodontal condition and the glycemic control of patients with diabetes type 2 when compared to non-surgical periodontal treatment alone.

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 Mesenchymal Stem Cells as a Key for Functional Integrity for Liver Cancer Treatment

Hepatocellular carcinoma (HCC) is the most common hepatobiliary malignancy with limited therapeutic options. On the other hand, melatonin is an indoleamine that modulates a variety of potential therapeutic effects. In addition to its important role in the regulation of sleep–wake rhythms, several previous studies linked the biologic effects of melatonin to various substantial endocrine, neural, immune and antioxidant functions, among others. Furthermore, the effects of melatonin could be influenced through receptor dependent and receptor independent manner. Among the other numerous physiological and therapeutic effects of melatonin, controlling the survival and differentiation of mesenchymal stem cells (MSCs) has been recently discussed. Given its controversial interaction, several previous reports revealed the therapeutic potential of MSCs in controlling the hepatocellular carcinoma (HCC). Taken together, the intention of the present review is to highlight the effects of melatonin and mesenchymal stem cells as a key for functional integrity for liver cancer treatment. We hope to provide solid piece of information that may be helpful in designing novel drug targets to control HCC.

Experimental Study on the Influence of Apigenin K and Melatonin in Socket Preservation as Bone Stimulators: An Experimental Study in Beagle Dogs

The aim is to evaluate whether apigenin K and melatonin M5250 were able to stimulate bone formation after tooth extraction at one, two, and three months follow-up. Six male beagle dogs were used. Apigenin K and melatonin M5250 immersed in hemostatic collagen sponges were placed in the third and fourth premolar and the first molar extracted sockets; the second premolar was used as control. At one, two, and three months, bone core biopsies were performed, and picrosirius–hematoxylin was used for the staining process. In the first month, a higher amount of calcified bone tissue was observed in the melatonin (77.87% ± 1.2%) and apigenin K (69.81% ± 1.8%) groups than the control group (57.27% ± 0.54%), with apparent discrepancies in values between the three groups (p < 0.04). In the second month, there was a considerable improvement in the results in the areas with melatonin (79.81% ± 0.11%) than in those of apigenin K (71.65% ± 0.52%) and control (64.77% ± 0.44%) (p < 0.04). In the third month, the number of mature bone was similar to all the groups. The creation of new bone was significant in the melatonin group (82.78% ± 0.87%), followed by the apigenin K group (78.76% ± 0.43%) and the control group (57.27% ± 0.11%). From this experimental study in dogs, it can be concluded that melatonin and apigenin K can accelerate the process of mineralization of the bone matrix, and thus the creation of laminae in the early stages of healing (1 month). Less reabsorption of the post-extraction sockets can be expected with the topical application of melatonin and apigenin K. It seems that the stimulatory effects of bone healing induced by the topical application of melatonin and apigenin K are defect-size-dependent, being more evident in small defects compared to larger defects.

Melatonin's Antineoplastic Potential Against Glioblastoma

Glioblastoma (GBM) is one of the most intransigent and aggressive brain tumors, and its treatment is extremely challenging and ineffective. To improve patients’ expectancy and quality of life, new therapeutic approaches were investigated. Melatonin is an endogenous indoleamine with an incredible variety of properties. Due to evidence demonstrating melatonin’s activity against several cancer hallmarks, there is growing interest in its use for preventing and treating cancer. In this review, we report on the potential effects of melatonin, alone or in combination with anticancer drugs, against GBM. We also summarize melatonin targets and/or the intracellular pathways involved. Moreover, we describe melatonin’s epigenetic activity responsible for its antineoplastic effects. To date, there are too few clinical studies (involving a small number of patients) investigating the antineoplastic effects of melatonin against GBM. Nevertheless, these studies described improvement of GBM patients’ quality of life and did not show significant adverse effects. In this review, we also report on studies regarding melatonin-like molecules with the tumor-suppressive properties of melatonin together with implemented pharmacokinetics. Melatonin effects and mechanisms of action against GBM require more research attention due to the unquestionably high potential of this multitasking indoleamine in clinical practice.

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.

Melatonin Synthesis and Function: Evolutionary History in Animals and Plants

Melatonin is an ancient molecule that can be traced back to the origin of life. Melatonin's initial function was likely that as a free radical scavenger. Melatonin presumably evolved in bacteria; it has been measured in both α-proteobacteria and in photosynthetic cyanobacteria. In early evolution, bacteria were phagocytosed by primitive eukaryotes for their nutrient value. According to the endosymbiotic theory, the ingested bacteria eventually developed a symbiotic association with their host eukaryotes. The ingested α-proteobacteria evolved into mitochondria while cyanobacteria became chloroplasts and both organelles retained their ability to produce melatonin. Since these organelles have persisted to the present day, all species that ever existed or currently exist may have or may continue to synthesize melatonin in their mitochondria (animals and plants) and chloroplasts (plants) where it functions as an antioxidant. Melatonin's other functions, including its multiple receptors, developed later in evolution. In present day animals, via receptor-mediated means, melatonin functions in the regulation of sleep, modulation of circadian rhythms, enhancement of immunity, as a multifunctional oncostatic agent, etc., while retaining its ability to reduce oxidative stress by processes that are, in part, receptor-independent. In plants, melatonin continues to function in reducing oxidative stress as well as in promoting seed germination and growth, improving stress resistance, stimulating the immune system and modulating circadian rhythms; a single melatonin receptor has been identified in land plants where it controls stomatal closure on leaves. The melatonin synthetic pathway varies somewhat between plants and animals. The amino acid, tryptophan, is the necessary precursor of melatonin in all taxa. In animals, tryptophan is initially hydroxylated to 5-hydroxytryptophan which is then decarboxylated with the formation of serotonin. Serotonin is either acetylated to N-acetylserotonin or it is methylated to form 5-methoxytryptamine; these products are either methylated or acetylated, respectively, to produce melatonin. In plants, tryptophan is first decarboxylated to tryptamine which is then hydroxylated to form serotonin.

The effects of melatonin supplementation in adjunct with non-surgical periodontal therapy on periodontal status, serum melatonin and inflammatory markers in type 2 diabetes mellitus patients with chronic periodontitis: a double-blind, placebo-controlled trial

BACKGROUND

Diabetes mellitus (DM) and periodontitis are two common chronic diseases with bidirectional relationship. Oxidative stress plays a key role in the pathogenesis of these two diseases. The aim of this study was to investigate the effects of melatonin supplementation in adjunct with non-surgical periodontal therapy on periodontal status, serum melatonin and inflammatory markers in type 2 DM patients with chronic periodontitis (CP).

MATERIALS AND METHODS

In this double-blind clinical trial study, 50 type 2 DM patients with CP were randomly allocated to the intervention and control groups. The intervention and control groups received either 6 mg melatonin or placebo (2 tablets) once a day. Serum levels of melatonin, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), hs-C-reactive protein (hs-CRP), clinical attachment loss (CAL), pocket depth (PD), bleeding on probing (BOP) and plaque index were evaluated in all subjects pre- and post-intervention.

RESULTS

Melatonin supplementation significantly increased the mean serum levels of melatonin after intervention. The mean changes of melatonin were significantly higher in intervention group compared with control group. IL-6 and hs-CRP levels were significantly (p = 0.008 and p = 0.017, respectively) reduced in the intervention group. The mean changes of IL-6 were significantly lower in the intervention group compared with the control group (p = 0.04). In the intervention group, PD and CAL were significantly decreased after intervention (p < 0.001). There were significant differences in the mean change of PD and CAL between the intervention and control groups after intervention (p < 0.001).

CONCLUSIONS

Melatonin supplementation in adjunct with non-surgical periodontal therapy might improve inflammatory and periodontal status in T2DM with CP.

Modulation of serine/threonine phosphatases by melatonin: therapeutic approaches in neurodegenerative diseases

Melatonin is an endogenous hormone produced by the pineal gland as well as many other tissues and organs. The natural decline in melatonin levels with ageing contributes significantly to the development of neurodegenerative disorders. Neurodegenerative diseases share common mechanisms of toxicity such as proteinopathy, mitochondrial dysfunction, metal dyshomeostasis, oxidative stress, neuroinflammation and an imbalance in the phosphorylation/dephosphorylation ratio. Several reports have proved the usefulness of melatonin in counteracting the events that lead to a neurodegenerative scenario. In this review, we have focused on the fact that melatonin could rectify the altered phosphorylation/dephosphorylation rate found in some neurodegenerative diseases by influencing the activity of phosphoprotein phosphatases. We analyse whether melatonin offers any protective activity towards these enzymes through a direct interaction. LINKED ARTICLES: This article is part of a themed section on Recent Developments in Research of Melatonin and its Potential Therapeutic Applications. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.16/issuetoc.

Pre-treatment with melatonin decreases abamectin induced toxicity in a nocturnal insect Spodoptera litura (Lepidoptera: Noctuidae)

AIM

Oxidative stress is an important component of the mechanism of pesticide toxicity. The aim of the present study was to investigate the time-dependent melatonin effects against abamectin-induced oxidative stress in a S.litura model. Larvae were divided into 5 different groups; (1) control group,(2) Melatonin group (4.3×10^-5M/100ml diet), (3) Abamectin group 1.5ml/L, (4) Pre-melatonin treated group (PM) (4.3×10^-5M/100ml diet) before abamectin exposure 1.5ml/L, (5) Post-melatonin treated group (TM) after abamectin exposure. Melatonin was supplemented via artificial diet in PM and TM animals during 24h.

MAIN METHODS

Midgut, fatbody, and hemolymph, were collected for the analysis of oxidative stress markers (Total ROS, GSH, nitrite, TBARS, LPO), antioxidant enzyme levels (SOD, GST, CAT, POX, APOX) in fifth instar larvae. Midgut damage was examined by using morphological analysis.

KEY FINDINGS

Our results observed that ABA group showed significant changes (p<0.001) in the ROS and carbonyl content in midgut. The increase of antioxidant enzyme levels (SOD, CAT, POX, and APOX) in midgut was led by the continuous free radical scavenger cascade of melatonin. Significant (p<0.01) increases in CAT and APOX levels were seen in the fatbody of PM and TM treated insects.

SIGNIFICANCE

In conclusion, the results of the study revealed that abamectin toxicity generates oxidative stress in the insect, while pre-melatonin treatment reduces this damage due to its antioxidant properties, especially POX levels in midgut, fatbody, and hemolymph. Therefore, indoleamine can play a vital role curtailing the abamectin toxicity in time dependent manner in S.litura.

Melatonin influences the sonic hedgehog signaling pathway in porcine cumulus oocyte complexes

Melatonin, which is synthesized in the pineal gland and peripheral reproductive organs, has antioxidant properties and regulates physiological processes. It is well known that melatonin affects in vitro maturation (IVM) of oocytes and embryonic development in many species. However, beneficial effects of melatonin on IVM have been explained mainly by indirect antioxidant effects and little information is available on the underlying mechanism by which melatonin directly acts on porcine cumulus oocyte complexes (COCs). Sonic hedgehog (Shh) signaling is important for follicle development, oocyte maturation, and embryo development, and there may be a relationship between melatonin and Shh signaling. To examine this, we designed three groups: (i) control, (ii) melatonin (10^-9  mol/L), and (iii) melatonin with cyclopamine (2 μmol/L; Shh signaling inhibitor). The aim of this study was to investigate the effects of these agents on cumulus expansion, oocyte maturation, embryo development after parthenogenetic activation (PA), gene expression in cumulus cells, oocytes and blastocysts, and protein expression in COCs. Melatonin significantly increased the proportion of COCs exhibiting complete cumulus expansion (degree 4), PA blastocyst formation rates, and total cell numbers, which were inhibited by addition of cyclopamine. Simultaneously, the expression of cumulus expansion-related genes (Ptgs1, Ptgs2, and Has2) and Shh signaling-related genes (Shh, Pthc1, Smo, and Gli1) and proteins (Ptch1, Smo, and Gli1) in cumulus cells was upregulated in the melatonin-treated group, and these effects were also inhibited by cyclopamine. In conclusion, our results suggest that Shh signaling mediates effects of melatonin to improve porcine cumulus expansion and subsequent embryo development.

Melatonin and periodontal tissues: Molecular and clinical perspectives

Periodontal disease is a frequent chronic inflammatory pathology that implies the destruction of the tissues supporting the teeth, which represents a high sanitary cost. It usually appears associated with other systemic conditions such as diabetes, metabolic syndrome, depression and Alzheimer disease among others. The presence of melatonin and its receptors in the oral cavity supports the hypothesis that this hormone could play a role in homeostasis of periodontal tissues. In the present review we will discuss the potential role of melatonin, a circadian synchronizing hormone, with proved antiinflammatory and antioxidant profile, in the pathogenesis and treatment of periodontitis. Particular emphasis will be placed on the role of the indolamine in the treatment of periodontal disease when this oral condition is comorbid with other pathologies that would also benefit from the therapeutic potential of melatonin and its analogs through diverse mechanisms.

Melatonin as a promising agent of regulating stem cell biology and its application in disease therapy

Stem cells have emerged as an important approach to repair and regenerate damaged tissues or organs and show great therapeutic potential in a variety of diseases. However, the low survival of engrafted stem cells still remains a major challenge for stem cell therapy. As a major hormone from the pineal gland, melatonin has been shown to play an important role in regulating the physiological and pathological functions of stem cells, such as promoting proliferation, migration and differentiation. Thus, melatonin combined with stem cell transplantation displayed promising application potential in neurodegenerative diseases, liver cirrhosis, wound healing, myocardial infarction, kidney ischemia injury, osteoporosis, etc. It exerts its physiological and pathological functions through its anti-oxidant, anti-inflammatory, anti-apoptosis and anti-ageing properties. Here, we summarize recent advances on exploring the biological role of melatonin in stem cells, and discuss its potential applications in stem cell-based therapy.

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.

Effects of melatonin and its analogues on neural stem cells

Neural stem cells (NSCs) are multipotent cells which are capable of self-replication and differentiation into neurons, astrocytes or oligodendrocytes in the central nervous system (CNS). NSCs are found in two main regions in the adult brain: the subgranular zone (SGZ) in the hippocampal dentate gyrus (DG) and the subventricular zone (SVZ). The recent discovery of NSCs in the adult mammalian brain has fostered a plethora of translational and preclinical studies to investigate novel approaches for the therapy of neurodegenerative diseases. Melatonin is the major secretory product synthesized and secreted by the pineal gland and shows both a wide distribution within phylogenetically distant organisms from bacteria to humans and a great functional versatility. Recently, accumulated experimental evidence showed that melatonin plays an important role in NSCs, including its proliferation, differentiation and survival, which are modulated by many factors including MAPK/ERK signaling pathway, histone acetylation, neurotrophic factors, transcription factors, and apoptotic genes. The purpose of this review is to summarize the beneficial effects of melatonin on NSCs and further to discuss the potential usage of melatonin and its derivatives or analogues in the treatment of CNS neurodegenerative diseases.

Effect of topical application of melatonin on serum levels of C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in patients with type 1 or type 2 diabetes and periodontal disease

Background

The present clinical trial study was designed to assess the effect of topical application of melatonin on serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and C-reactive protein (CRP) in patients with diabetes and periodontal disease in comparison with healthy controls.

Material and Methods

Serum levels of TNF-α and IL-6 were measured by enzyme-linked immunosorbent assay and CRP by nephelometry by using the proper commercial kits in 30 patients with diabetes and periodontal disease, and also in a control group of 30 healthy subjects. Periodontograms were performed using the Florida Probe®. Patients with diabetes were treated with a topical application of melatonin (1% orabase cream formula) once daily for 20 days. Healthy subjects were treated with a placebo orabase cream.

Results

Patients with diabetes and periodontal disease had significantly higher mean levels of serum TNF-α, IL-6 and CRP than healthy subjects (P < 0.001). Following topical melatonin application, there was a statistically significant decrease in the gingival index and pocket depth (P < 0.001) as well as a significant decrease in IL-6 and CRP serum levels (P < 0.001). Local melatonin application in patients with diabetes and periodontal disease resulted in a significant decrease in CRP and IL-6 serum levels as well as an improvement in the gingival index and pocket depth. Patients with periodontal disease had significantly higher serum CRP, IL-6 and TNF-α values by comparison with healthy subjects.

Conclusions

We conclude that melatonin can modulate the inflammatory action of these molecules in periodontal patients.

Key words:Melatonin, periodontal disease, diabetes mellitus, interleukin-6, tumor necrosis factor-alpha, C-reactive protein, inflammatory markers.

Use of melatonin in oral health and as dental premedication

Anxiety is a common problem in dentistry which could affect the correct treatment and involve failure. Oral premedication is needed to treat several anxious patients. Many people are so highly anxious that oral sedation is not effective and need to be under deep sedation or even general anaesthesia in order to receive dental care. In these patients, due to a high level of anxiety, even the insertion of an intravenous catheter can be difficult. Benzodiazepines have been the most commonly used anxiolytic in these cases, but many may be associated with paradoxical reactions. Melatonin has a good potential to be used in this field as alternative to benzodiazepines because it may induce a natural sleepiness and improve sedation. The purpose of this paper was to summarize what is known about the use of melatonin in oral health and as dental premedication in anxious dental patients. Databases were searched for the relevant published literature to 30 April 2015. The following search items were used in various combinations: melatonin, premedication, anxiety, dental, sedation and anaesthesia. Few articles were found about this aspect, and the use of melatonin is still a controversial aspect in dental field. More detailed/specific studies are necessary to extend the therapeutic possibilities of melatonin as premedication in dentistry.

Melatonin as a candidate therapeutic drug for protecting bone cells from chlorhexidine-induced damage

BACKGROUND

Melatonin was proposed for use in periodontitis and peri-implantitis therapy due to its bone-supportive effects. This issue is of interest because standard adjuvant antiseptics, namely chlorhexidine (CHX), prove damaging for osteoblasts. Thus, the aim of this study is to investigate if melatonin is suitable as an auxiliary agent for protecting osteoblasts from CHX damage.

METHODS

MC3T3 osteoblast response was determined following administration of various CHX concentrations in the absence or presence of melatonin. Osteoblast morphology was evaluated, total reactive oxygen species (ROS) and superoxide levels were quantified, ratios of apoptotic and necrotic cells were identified by flow cytometry, metabolic activity of remaining cells was assessed, and effects were calculated with repeated measures analysis and post hoc P value adjustment.

RESULTS

CHX led to poor morphology, increased total ROS and superoxide levels, and rigorously diminished the number of vital and metabolic active osteoblasts in a concentration-dependent manner. However, simultaneous melatonin supply supported cell morphogenesis and growth, reduced ROS and superoxide generation, shifted the percentage of CHX-damaged cells from necrotic/late to early apoptotic events, and modulated metabolic activity in osteoblasts.

CONCLUSION

These data reveal that melatonin protects osteoblasts in the CHX context, thereby implicating melatonin as a promising drug in periodontitis and peri-implantitis treatment.

Involvement of nuclear receptor RZR/RORγ in melatonin-induced HIF-1α inactivation in SGC-7901 human gastric cancer cells

The melatonin nuclear receptor is an orphan member of the nuclear receptor superfamily RZR/ROR, which consists of three subtypes (α, β and γ), suggesting that immunomodulatory and antitumor effects through the intracellular action of melatonin depend on nuclear signaling. In the present study, the biological mechanisms of melatonin were elucidated in association with the RZR/RORγ pathway in SGC-7901 human gastric cancer cells under hypoxia. Melatonin suppressed the activity of RZR/RORγ and SUMO-specific protease 1 (SENP1) signaling pathway, which is essential for stabilization of hypoxia‑inducible factor-1α (HIF‑1α) during hypoxia. Furthermore, melatonin inhibited the stability of HIF-1α in a time- and conce-ntration-dependent manner in SGC-7901 human gastric cancer cells during hypoxia. Consistently, siRNA-RZR/RORγ effectively blocked the expression of SENP1, HIF-1α and vascular endothelial growth factor (VEGF) production in SGC-7901 cells under hypoxia, suggesting the role of nuclear receptor RZR/RORγ in melatonin-inhibited HIF-1α and VEGF accumulation. Moreover, siRNA RZR/RORγ obviously antagonized to inhibit the action of the gastric cancer cell proliferation by melatonin. Our findings suggest that melatonin suppresses HIF-1α accumulation and VEGF generation via inhibition of melatonin nuclear receptor RZR/RORγ in SGC-7901 cells under hypoxia.

Melatonin: a potential intervention for hepatic steatosis

Melatonin (N-acetyl-5-methoxytryptamine, MLT) is a neuroendocrine hormone, which is primarily synthesized by the pineal gland in vertebrates. Melatonin is a remarkable molecule with diverse biological and physiological actions and is involved in the regulation of various important functions such as circadian rhythm, energy metabolism, the reproductive system, the cardiovascular system, and the neuropsychiatric system. It also plays a role in disease by having anti-neoplastic and anti-osteoarthritic effects among others. Recently, research has focused on the roles of melatonin in oxidative stress, lipid metabolism, and hepatic steatosis and its potential therapeutic roles.

Effects of melatonin on the proliferation and apoptosis of sheep granulosa cells under thermal stress

The cross-talk between oocyte and somatic cells plays a crucial role in the regulation of follicular development and oocyte maturation. As a result, granulosa cell apoptosis causes follicular atresia. In this study, sheep granulosa cells were cultured under thermal stress to induce apoptosis, and melatonin (MT) was examined to evaluate its potential effects on heat-induced granulosa cell injury. The results demonstrated that the Colony Forming Efficiency (CFE) of granulosa cells was significantly decreased (heat 19.70% ± 1.29% vs. control 26.96% ± 1.81%, p < 0.05) and the apoptosis rate was significantly increased (heat 56.16% ± 13.95%vs. control 22.80% ± 12.16%, p < 0.05) in granulosa cells with thermal stress compared with the control group. Melatonin (10⁻⁷ M) remarkably reduced the negative effects caused by thermal stress in the granulosa cells. This reduction was indicated by the improved CFE and decreased apoptotic rate of these cells. The beneficial effects of melatonin on thermal stressed granulosa cells were not inhibited by its membrane receptor antagonist luzindole. A mechanistic exploration indicated that melatonin (10⁻⁷ M) down-regulated p53 and up-regulated Bcl-2 and LHR gene expression of granulosa cells under thermal stress. This study provides evidence for the molecular mechanisms of the protective effects of melatonin on granulosa cells during thermal stress.

Fundamental issues related to the origin of melatonin and melatonin isomers during evolution: relation to their biological functions

Melatonin and melatonin isomers exist and/or coexist in living organisms including yeasts, bacteria and plants. The levels of melatonin isomers are significantly higher than that of melatonin in some plants and in several fermented products such as in wine and bread. Currently, there are no reports documenting the presence of melatonin isomers in vertebrates. From an evolutionary point of view, it is unlikely that melatonin isomers do not exist in vertebrates. On the other hand, large quantities of the microbial flora exist in the gut of the vertebrates. These microorganisms frequently exchange materials with the host. Melatonin isomers, which are produced by these organisms inevitably enter the host's system. The origins of melatonin and its isomers can be traced back to photosynthetic bacteria and other primitive unicellular organisms. Since some of these bacteria are believed to be the precursors of mitochondria and chloroplasts these cellular organelles may be the primary sites of melatonin production in animals or in plants, respectively. Phylogenic analysis based on its rate-limiting synthetic enzyme, serotonin N-acetyltransferase (SNAT), indicates its multiple origins during evolution. Therefore, it is likely that melatonin and its isomer are also present in the domain of archaea, which perhaps require these molecules to protect them against hostile environments including extremely high or low temperature. Evidence indicates that the initial and primary function of melatonin and its isomers was to serve as the first-line of defence against oxidative stress and all other functions were acquired during evolution either by the process of adoption or by the extension of its antioxidative capacity.

Pharmacological characterization of a highly selective and potent partial agonist of the MT₂ melatonin receptor

BACKGROUND/AIMS

The MT₂ melatonin receptor is a potential target for treating circadian rhythm sleep disorders. This study aims to characterize the recently identified MT₂ melatonin receptor agonist.

METHODS

The pharmacological properties of the MT₂ melatonin receptor-selective agonist as exemplified by compound 1 [N-(2-[7-benzyl-1,6-dihydro-2H-indeno(5,4-b)furan-8-yl]ethyl)acetamide] were evaluated by use of cell-free binding and cell-based functional assays.

RESULTS

Competition binding assays using 2-[(125)I]iodomelatonin revealed rapid, reversible, and high-affinity binding of compound 1 to human, mouse, and rat MT₂ melatonin receptors. cAMP, ERK1/2, and PathHunter β-arrestin recruitment assays revealed partial agonist activities. However, compound 1 induced a more intense internalization of human MT₂ melatonin receptor than melatonin. Based on studies using structurally related analogs of compound 1, we further demonstrated that the extent of internalization is independent of the intrinsic efficacy of agonists.

CONCLUSION

These findings provide novel insights into the relationship between intrinsic agonist efficacy and agonist-induced internalization and demonstrate that compound 1 could serve as a pharmacological tool for future studies to elucidate the detailed molecular mechanism of MT₂ receptor internalization.

Action of melatonin on squamous cell carcinoma and other tumors of the oral cavity (Review)

Melatonin (MLT; N-acetyl-5-metoxy-tryptamine) is a hormone that is principally synthesized in the pineal gland. MLT has been shown to exhibit a variety of functions. The hormone, which is a free radical scavenger, plays an immunomodulatory role, stimulates the proliferation and synthesis of type I collagen and promotes bone formation. Moreover, MLT exerts oncostatic activity through several biological mechanisms, including antiproliferative functions, stimulation of anticancer immunity, modulation of oncogene expression and anti-inflammatory, antioxidant and antiangiogenic effects. In addition, MLT inhibits human cancer cell growth in culture, and previous clinical studies have also confirmed its anticancer properties in vivo. With regard to the underlying mechanisms of MLT in tumor processes, including oral cavity tumors such as epidermoid carcinoma, knowledge of the role played by the MT1 and 2 membrane receptors, MT3 and the calmodulin cytosolic binding sites, as well as the nuclear receptors of the RZR/ROR family, is increasing. It has been hypothesized that exogenous restoration of MT1 (MTNR1A) expression inhibits the growth of oral squamous cell carcinoma cells lacking the expression of the receptor. The tumor suppressing functions of MLT and the presence of the MT1 receptor in various tumors indicate that the receptor may play a pivotal role in oral carcinogenesis. The current review discusses the clinical significance of MLT in oral cancer.

Subcellular distribution of melatonin receptors in human parotid glands

The hormone melatonin influences oral health through a variety of actions, such as anti-inflammatory, anti-oxidant, immunomodulatory and antitumour. Many of these melatonin functions are mediated by a family of membrane receptors expressed in the oral epithelium and salivary glands. Using immunoblotting and immunohistochemistry, recent studies have shown that the melatonin membrane receptors, MT1 and MT2, are present in rat and human salivary glands. To date, no investigation has dealt with the ultrastructural distribution of the melatonin receptors. This was the aim of the present study, using the immunogold method applied to the human parotid gland. Reactivity to MT1 and, with less intensity, to MT2 appeared in the secretory granules of acinar cells and in the cytoplasmic vesicles of both acinar and ductal cells. Plasma membranes were also stained, albeit slightly. The peculiar intracytoplasmic distribution of these receptors may indicate that there is an uptake/transport system for melatonin from the circulation into the saliva.

Impact of melatonin on immunity: a review

Melatonin is a hormone produced by the pineal gland. In addition to its hormonal effect, it has strong antioxidant properties. Melatonin is probably best known for its ability to control circadian rhythm; it is sold in many countries as a supplement or drug for improving of sleep quality. However, melatonin’s effect is not limited to control of circadian rhythm:. it is involved in other effects, including cell cycle control and regulation of several important enzymes, including inhibition of inducible nitric oxide synthase. Melatonin affects immunity as well. It can modulate the immune response on disparate levels with a significant effect on inflammation. The role of melatonin in body regulatory process is not well understood; only limited conclusions can be drawn from known data. The current review attempts to summarize both basic facts about melatonin’s effects and propose research on the lesser known issues in the future.

Melatonin effects on hard tissues: bone and tooth

Melatonin is an endogenous hormone rhythmically produced in the pineal gland under the control of the suprachiasmatic nucleus (SCN) and the light/dark cycle. This indole plays an important role in many physiological processes including circadian entrainment, blood pressure regulation, seasonal reproduction, ovarian physiology, immune function, etc. Recently, the investigation and applications of melatonin in the hard tissues bone and tooth have received great attention. Melatonin has been investigated relative to bone remolding, osteoporosis, osseointegration of dental implants and dentine formation. In the present review, we discuss the large body of published evidence and review data of melatonin effects on hard tissues, specifically, bone and tooth.

Immune modulatory and antioxidant effects of melatonin in experimental periodontitis in rats

Melatonin is an important antioxidant, and through its anti-inflammatory effects it can control immune responses, oxidative stress, and defense cell infiltration. Periodontitis is a disease of the oral cavity and the generation of free radicals is an important consideration in this disease. Therefore, we examined the immune-modulatory and antioxidant roles of melatonin in the treatment of periodontitis. In all, 30 male Wistar rats were randomly divided into three groups: the control group, the periodontitis-induced (PED) group, and the periodontitis+melatonin treatment (MEL+PED) group. The control group received no treatment, whereas periodontitis was induced in both the PED and the MEL+PED groups, with the MEL+PED group being treated with systemic melatonin. For the periodontitis-induced groups, the rats' mandibular first molar teeth were ligatured (3-0 cotton) in a submarginal position for 4 weeks, and then the ligature was removed. After removal of the ligature, melatonin was administered only to the MEL+PED group (an ip dose of 10mg/kg body wt for 15 days at 11:00 PM each day). In the histological examination, the MEL+PED group, which received the melatonin, showed reduced inflammatory cytokines (IL-1β, from 97.47 to 84.24pg/ml; TNF-α, from 0.22530 to 0.22519pg/ml), regulated oxidative stress parameters (MDA, from 41,458 to 30,708nmol/g; GSH, from 18,166 to 25,858nmol/mg), and less periodontal tissue destruction (CEJ-PL, lingual, from 244.54 to 140.57μm; buccal, from 235.6 to 158.93μm; and CEJ-BC, lingual, from 383.65 to 287.76μm; buccal, from 391.92 to 296.12μm). From these findings we conclude that, even when periodontitis was induced, melatonin reduced the oxidative damage in the rats' periodontal tissue by inhibiting the inflammatory effects and by restoring the antioxidants.

MT1 melatonin receptor expression in Warthin's tumor

We contribute the first immunohistochemical study of MT1 melatonin receptor in Warthin's tumor and normal parotid gland. All 14 Warthin's tumors studied showed intense cytoplasmic positivity for MT1 receptor in all cylindrical epithelial cells lining spaces and a less intense positivity in basal cells. The lymphoid component accompanying the tumor was always negative for MT1 receptor. The parotid structure surrounding the tumor showed intense cytoplasmic positivity in all cells lining excretory ducts (lobar and lobulillar), with a lesser and focal positivity in cells of the acinar component. The biological activity of MT1 receptor in epithelial cells lining parotid excretory ducts may resemble its activity in Warthin's tumor cells. Hence, we propose Warthin's tumor as a useful positive control in immunohistochemical studies of MT1 melatonin receptor.

Non-surgical periodontal therapy influences salivary melatonin levels

OBJECTIVES

Melatonin is a hormone, which is involved in the control of the circadian rhythm, but also acts as an antioxidant and immune modulator. Previous studies reported decreased salivary and serum melatonin levels in periodontitis. This prospective cohort trial assessed the effect of non-surgical periodontal therapy on melatonin levels.

METHODS

Salivary and serum samples of 60 participants (30 patients suffering from a severe generalized form of periodontitis, 30 healthy controls) were collected at baseline and 19 samples of periodontitis patients after treatment. Salivary and serum melatonin levels were determined by a commercially available ELISA kit and serum C-reactive protein (CRP) by a routine laboratory test.

RESULTS

At baseline, periodontitis patients showed significantly increased serum CRP values and significantly decreased salivary melatonin levels compared to the control group. Clinical periodontal parameters significantly correlated with salivary melatonin levels and serum CRP. Periodontal therapy resulted in a recovery of the decreased salivary melatonin levels and a negative correlation was detected for the changes of salivary melatonin and the inflammatory parameter bleeding on probing. Serum melatonin levels showed no significant differences.

CONCLUSIONS

Salivary melatonin levels recovered after periodontal therapy and correlated with a decrease of local periodontal inflammation. This may imply the local involvement of melatonin in the pathogenesis of periodontitis due to its antioxidant abilities. However, the exact role of melatonin in periodontal disease remains to be investigated in future trials.

CLINICAL RELEVANCE

The present results suggest salivary melatonin as a risk indicator for the severity of periodontal disease.