title: Induction of cyclooxygenase-2 mRNA and protein expression in human gingival fibroblasts stimulated with nicotine.
abstract: BACKGROUND
  Cigarette smoking is a major risk factor in the development and further progression of periodontal diseases. COX-2 is an inducible enzyme believed to be responsible for prostaglandin synthesis at site of inflammation. Currently, there is limited information on the regulation of COX-2 expression in smoking-associated periodontal disease.
  
  
  OBJECTIVE
  The aim of the present study was to investigate the effects of nicotine on the expression of cyclooxygenase-2 (COX-2) mRNA gene and protein in cultured human gingival fibroblasts (HGFs). Furthermore, to elucidate whether induction of COX-2 may be associated with nicotine- induced cytotoxicity, NS-398 (a selective COX-2 inhibitor), was added to test its protective effect.
  
  
  METHODS
  The quantitative reverse-transcriptase polymerase chain reaction and Western blot assays were used to investigate the effects of human HGFs exposed to nicotine. In addition, NS-398 was added to test how it modulated the effects of nicotine.
  
  
  RESULTS
  The exposure of quiescent human HGFs to nicotine resulted in the induction of COX-2 mRNA expression. The levels of the COX-2 mRNAs increased about 1.5 and 2.5 fold after exposure to 2.5 and 15 mm nicotine for 2 h (P < 0.05), respectively. Moreover, the peak of COX-2 mRNA levels induced by nicotine was 10 mm at 2 h incubation period. Investigations of the time dependence of COX-2 mRNA expression in nicotine-treated HGFs revealed a rapid accumulation of the transcript, a signal first detectable at 30 min and diminished to control level after 8 h. In addition, 10 mm nicotine also induced COX-2 protein expression in HGFs. The kinetics of this response showed that COX-2 was detectable at 4 h and diminished nearly to control level after 24 h. NS-398 at non-cytotoxic dose is not able to prevent nicotine-induced cytotoxicity.
  
  
  CONCLUSIONS
  Taken together, the activation of COX-2 expression by nicotine suggests a potential role for nicotine in the pathogenesis of smoking-associated periodontal disease. In addition, nicotine-induced cytotoxicity is not directly via the induction of COX-2 expression.
authors.affiliation: Oral Medicine Center, Chung Shan Medical University Hospital, Taichung, Taiwan. cyc@csmu.edu.tw
authors.forename: Yu-Chao
authors.initials: YC
authors.lastname: Chang
authors.forename: Chung-Hung
authors.initials: CH
authors.lastname: Tsai
authors.forename: Shyh-Hwang
authors.initials: SH
authors.lastname: Yang
authors.forename: Chia-Ming
authors.initials: CM
authors.lastname: Liu
authors.forename: Ming-Yung
authors.initials: MY
authors.lastname: Chou
mesh_terms: D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects*; D005347:Fibroblasts / Q000201:enzymology; D005881:Gingiva / Q000166:cytology / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D008565:Membrane Proteins; D009538:Nicotine / Q000633:toxicity*; D018722:Nicotinic Agonists / Q000633:toxicity*; D009578:Nitrobenzenes / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D018722:Nicotinic Agonists; D009578:Nitrobenzenes; D012333:RNA, Messenger; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D009538:Nicotine; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases