Preliminary Evaluation of Human Gingiva as an Extrapineal Site of Melatonin Biosynthesis in States of Periodontal Health and Disease

Introduction: Melatonin is a pineal gland hormone that plays an important role in periodontal homeostasis. Extra pineal melatonin production has been found to occur in tissues like the ovaries, retina and gastrointestinal tract. It is not known if the human gingiva could synthesise melatonin and whether melatonin receptors are present in the gingival tissues. Aim: To investigate if human gingiva is an extrapineal site of melatonin biosynthesis in non smokers and current smokers with and without chronic generalised periodontitis. Materials and Methods: The present study has a case control design with a total of 60 participants divided into four groups namely, Periodontally Healthy Non smokers (PHN)-Group 1, Non smokers with Chronic generalised Periodontitis (NCP)-Group 2, Periodontally Healthy current Smokers (PHS)-Group 3, and current Smokers with Chronic generalised Periodontits (SCP)- Group 4. Gingival tissue samples were obtained from the study participants after obtaining informed consent, using an aseptic protocol. Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) was carried out to assess the presence of the genes encoding N-Acetyl Transferase (AANAT), Hydroxyindolyl-OMethyltransferase (HIOMT), Melatonin Receptor 1 (MT1) and Melatonin Receptor 2 (MT2). Further flow cytometry experiments were carried out in freshly obtained gingival tissue samples to quantify melatonin receptors. Immunohistochemistry experiment was performed on paraffin embedded tissue sections to study the qualitative distribution of melatonin receptors. The results were documented and analysed using SPSS software version 23.0. Results: The current study showed that the human gingival tissues are an extrapineal site of melatonin biosynthesis. RTPCR, flow cytometry and immunohistochemistry techniques revealed that MT1 receptor was present in the human gingiva. Furthermore statistical analysis revealed that the expression of AANAT, HIOMT and MT1 genes and the MT1 receptor protein levels were significantly lower in current smokers with and without chronic generalised periodontitis compared to non smokers. Conclusion: It can be concluded that the gingiva could synthesise melatonin as a defense mechanism to protect against oxidative stress and inflammation. Habits like smoking can reduce the levels of gingival melatonin and MT 1 receptor expression which could reduce the cytoprotective benefits of melatonin.