title: Increased melatonin in oral mucosal tissue of oral lichen planus (OLP) patients: A possible link between melatonin and its role in oral mucosal inflammation.
abstract: OBJECTIVE
  The existence of extra-pineal melatonin has been observed in various tissues. No prior studies of melatonin in human oral mucosal tissue under the condition of chronic inflammation have been reported. The aim of this study was to investigate the presence of melatonin in oral mucosal tissue of patients with oral lichen planus (OLP) which was considered as a chronic inflammatory immune-mediated disease causing oral mucosal damage and ulcerations.
  
  
  METHODS
  Sections from formalin-fixed and paraffin-embedded oral mucosal tissue of OLP patients (n=30), and control subjects (n=30) were used in this study. Immunohistochemical staining was performed and the semiquantitative scoring system was used to assess the levels of arylalkylamine-N-acetyltransferase (AANAT: a rate-limiting enzyme in the biosynthesis pathway of melatonin), melatonin, and melatonin receptor 1 (MT1) in oral mucosa of OLP patients and normal oral mucosa of control subjects.
  
  
  RESULTS
  AANAT, melatonin, and MT1were detected in oral mucosal tissue of OLP patients and control subjects. Immunostaining scores of AANAT, melatonin, and MT1 in oral mucosal tissue of OLP patients were significantly higher than those in control subjects (p=0.002, p<0.001, and p=0.031, respectively).
  
  
  CONCLUSIONS
  Increased levels of AANAT, melatonin, and MT1 in the inflamed oral mucosal tissue of OLP patients imply that chronic inflammation may induce the local biosynthesis of melatonin via AANAT, and may enhance the action of melatonin via MT1.
authors.affiliation: Dental Hospital, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Kirawut
authors.initials: K
authors.lastname: Luengtrakoon
authors.affiliation: Sirindhorn College of Public Health Khon Kaen, Khon Kaen, Thailand.
authors.forename: Worraned
authors.initials: W
authors.lastname: Wannakasemsuk
authors.affiliation: Faculty of Dentistry, Phayao University, Phayao, Thailand.
authors.forename: Vilasinee
authors.initials: V
authors.lastname: Vichitrananda
authors.affiliation: Research Group of Chronic Inflammatory Oral Diseases and Systemic Diseases Associated with Oral Health, Khon Kaen University, Khon Kaen, Thailand; Department of Oral Diagnosis, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Poramaporn
authors.initials: P
authors.lastname: Klanrit
authors.affiliation: Research Group of Chronic Inflammatory Oral Diseases and Systemic Diseases Associated with Oral Health, Khon Kaen University, Khon Kaen, Thailand; Department of Periodontology, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Doosadee
authors.initials: D
authors.lastname: Hormdee
authors.affiliation: Department of Community Dentistry, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Rajda
authors.initials: R
authors.lastname: Noisombut
authors.affiliation: Research Group of Chronic Inflammatory Oral Diseases and Systemic Diseases Associated with Oral Health, Khon Kaen University, Khon Kaen, Thailand; Department of Oral Diagnosis, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand. Electronic address: cponla@kku.ac.th.
authors.forename: Ponlatham
authors.initials: P
authors.lastname: Chaiyarit
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D047068:Arylalkylamine N-Acetyltransferase / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000378:metabolism*; D017676:Lichen Planus, Oral / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D008875:Middle Aged; D009061:Mouth Mucosa / Q000378:metabolism*
chemical_list: C478879:AANAT protein, human; D047068:Arylalkylamine N-Acetyltransferase; D008550:Melatonin
keywords: Arylalkylamine-N-acetyltransferase; Inflammation; Melatonin; Melatonin receptor; Oral lichen planus