Analysis and Evaluation of the Effects of Melatonin on Oral Keratinocytes: A Pilot Study

Objective: Twenty to 30 percent of children in cross-sectional studies have significant bedtime problems or night waking. Melatonin, a synthetic form of the hormone produced by the pineal gland as a biomarker of the circadian system, is a commonly used nonprescription pharmacologic treatment for sleep disorders in children. Many studies have demonstrated the effect of melatonin supplementation on sleep duration and sleep quality, which can improve overall systemic health and disease prevention. However, despite the growing number of studies demonstrating the effects of melatonin to improve disordered sleep, no available studies have evaluated the effects of melatonin on normal oral tissues. Based upon this lack of knowledge, the primary objective of this study is to evaluate any potential effects of melatonin on normal oral cells and tissues within the physiologically relevant (supplementation) range.

Methods: Normal oral keratinocytes (OKF4) and human gingival fibroblasts (HGF-1) were obtained and cultured for this study. Melatonin was administered in 96-well growth assays at supplement-equivalent physiologic concentrations at the low, mid and high range (1, 5 and 10 ug/uL) to determine any effects on cellular growth and proliferation. Changes in cellular viability and expression of cell cycle and apoptosis-related pathways were also evaluated.

Results: Curvilinear U-shaped dose responses were observed in OKF cells under melatonin administration, ranging from -11.4% (low), to a maximum of -13.6% (mid) and -5.0% (high) compared with non-treated controls, p=0.029. Dose-responses among HGF-1 cells ranged from +12.1% (low), +17.4% (mid), and +5.0% (high), p=0.021. No changes in cellular viability were observed between control and experimental cells. However, qPCR screening of total RNA revealed significant changes in cell cycle related pathways, including c-myc, GAPDH and P53 but no changes in any apoptosis-related pathways, including Bcl-2, Bax, caspase-3, caspase-8 and caspase-9.

Conclusions: This study demonstrated that melatonin does affect growth but not viability among these cell lines, which was found to be dose-dependent. These results suggest that melatonin may have some limited effects on oral tissues that may influence wound healing and repair but may not affect normal physiologic function or other cellular pathways. In agreement with other pediatric literature supporting the safety of melatonin use, this pilot study does not reveal any deleterious effects that would caution against its use in children or adults.