Melatonin: a novel indolamine in oral health and disease

Effect of nonsurgical periodontal therapy on salivary melatonin levels in patients with periodontal disease

Context

Periodontitis is an inflammatory disease in which periodontal tissues are damaged as a result of an imbalance in the oxidant/antioxidant systems. Melatonin is one hormone that controls circadian rhythms and is also an antioxidant and immune modulator.

Aim

The present study was aimed to evaluate the effect of scaling and root planing (SRP) on salivary melatonin levels (SM) in patients with periodontal disease.

Settings and Design

A single-center clinical trial was conducted to evaluate the effect of SRP on SM levels in patients with periodontal disease.

Materials and Methods

Forty-five participants of age 30-60 years were equally divided into three groups: 15 healthy participants, 15 participants with gingivitis, and 15 participants with periodontitis. Unstimulated salivary samples were collected from all the participants at baseline and 1 month after SRP from participants of gingivitis and periodontitis group and SM levels were determined by commercially available ELISA kit.

Statistical Analysis Used

Group comparisons were made using t-test. The level of significance was set at a P < 0.05 for all tests.

Results

SM levels were significantly lower in the chronic periodontitis group. There was a significant improvement in clinical parameters and SM levels in both chronic periodontitis and gingivitis groups after SRP.

Conclusion

This study determined that there is a negative correlation between SM levels and the severity of periodontal disease and showed a significant increase in SM levels after SRP, suggesting that melatonin might have a protective role against periodontal disease and can be considered as an effective biomarker.

The Risk of Night Shift Workers to the Glucose Blood Levels, Saliva, and Dental Caries

OBJECTIVE

This study aimed to provide the correlation of circadian rhythms of night shift workers with blood glucose levels, saliva, and dental caries.

MATERIALS AND METHODS

This study was conducted on night shift and nonshift workers to measure fasting blood glucose (FBG), 2-hour postprandial blood glucose (2-PP BG), saliva flow rate, pH saliva, and caries with the decay-missing-filled total (DMF-T) index. Data analysis was done using independent t-test and correlation test with Pearson correlation.

RESULTS

There were significant differences in night shift and nonshift workers in FBG (p = 0.000), 2-PP BG (p = 0.000), flow rate saliva (p = 0.000), and DMF-T index (p = 0.001). Correlation test showed positive correlation between FBG and pH saliva (r = 0.42, p = 0.029) and DMF-T index (r = 0.521, p = 0.005) of night shift workers. The 2-PP BG also showed positive correlation with pH saliva (r = 0.493, p = 0.009) and DMF-T index (r = 0.743, p = 0.000). The DMF-T index showed negative correlation with flow rate saliva (r = -0.398, p = 0.04). In the nonshift workers, correlation test showed a correlation between FBG and DMF-T index (r = 0.384, p = 0.048). The DMF-T index showed correlation with flow rate saliva (r = 0.6, p = 0.001).

CONCLUSION

There is a circadian rhythm correlation between night shift workers to blood glucose levels, flow rate saliva, pH saliva, and dental caries.

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.

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.

Melatonin reduces ulcerative colitis-associated local and systemic damage in mice: investigation on possible mechanisms

BACKGROUND AND AIMS

Ulcerative colitis (UC) is a chronic gastrointestinal disorder. Substantial research reveals that melatonin has beneficial effects in ulcerative colitis both experimentally and clinically. We have previously reported that ulcerative colitis was associated with local and systemic damage in mice. The purpose of this study was to reveal the novel targets of melatonin in its protective mechanism against ulcerative colitis in mice. We also wished to determine whether or not melatonin protected against ulcerative colitis-induced systemic damage in mice.

METHODS

Ulcerative colitis was induced in mice by use of 3% (w/v) dextran sulfate sodium for two cycles. One cycle comprised 7 days of DSS-treated water followed by 14 days of normal drinking water. Melatonin was administered at doses of 2, 4, or 8 mg/kg bw/day, po throughout. The effect of melatonin in mice with UC was evaluated by use of biochemical data, histological evaluation, comet and micronucleus assays, immunohistochemistry, and western blot analysis.

RESULTS

The results indicated that melatonin treatment ameliorated the severity of ulcerative colitis by modulating a variety of molecular targets, for example nuclear factor kappa B, cyclooxygenase-2, interleukin 17, signal transducer and activator of transcription 3, nuclear erythroid 2-related factor 2, matrix metalloproteinase-9, and connective tissue growth factor. Further, ulcerative colitis increased gut permeability, plasma lipopolysaccharide level, systemic inflammation, and genotoxicity. Melatonin treatment led to mucosal healing and reduced ulcerative colitis-induced elevated gut permeability and reduced the plasma LPS level, systemic inflammation, and genotoxicity.

CONCLUSION

Melatonin ameliorated ulcerative colitis-associated local and systemic damage in mice.

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.