Anti-inflammatory Effect of Melatonin by Reduction of IL-1β Gene Expression on Human Dental Pulp Cells

Objectives: Melatonin is considered as a major chronobiotic hormone produced mainly by the pineal gland. It was suggested that melatonin at the site of inflamed lesion might play a role in inflammatory response via NF-kB pathway. It was also speculated that melatonin might play a cytoprotective role through its anti-oxidative and anti-inflammatory properties. However, no prior studies have investigated the biological effects of melatonin on human dental pulp cells. This study was aimed to determine the anti-inflammatory effect of melatonin on LPS-stimulated human dental pulp cells.

Methods: Primary dental pulp cells were isolated from human dental pulp tissue using an explant method. Then the dental pulp cells were treated with LPS (20 ug/ml) and melatonin with various concentrations (1mM. 1μM, 1nM and 1 pM) for 24 hours. The production of IL-1β mRNA was determined by reverse transcriptase-polymerase chain transcription (RT-PCR). Differences in expression of IL-1β mRNA between control and experimental groups were analyzed by one-way ANOVA test.
Results: LPS-induced dental pulp cells expressed higher levels of IL-1β mRNA as compared with the control group. LPS-induced dental pulp cells treated with 1 mM melatonin expressed lower levels of IL-1β mRNA as compared with the LPS-induced dental pulp cells (p = 0.01).
Conclusions: This study demonstrated an anti-inflammatory effect of melatonin on LPS-induced dental pulp cells by reduction of IL-1β mRNA expression. These findings imply that melatonin with appropriate concentrations may be beneficial for cytoprotection of dental pulp cells