title: Effect of Porphyromonas gingivalis on citrullination of proteins by macrophages in vitro.
abstract: BACKGROUND
  Citrullination of proteins within inflamed periodontal tissues may provide an important link between periodontitis and rheumatoid arthritis. The aim of this study is to determine whether the presence of Porphyromonas gingivalis peptidylarginine deiminase (PPAD) can influence citrullination of proteins by either increasing the amount of local citrullinated protein or influencing the peptidylarginine deiminase (PAD) enzymes found in the monocyte/macrophage population.
  
  
  METHODS
  Human peripheral blood monocytes and macrophages were incubated in the presence of live or heat-killed P. gingivalis. Expression of PAD2 and PAD4, PPAD, and citrullinated proteins were assessed by either a combination of real-time polymerase chain reaction, Western blotting, or a colorimetric assay.
  
  
  RESULTS
  PPAD was detected only in mononuclear cells incubated in the presence of live P. gingivalis and resulted in increased extracellular citrullination. Endogenous PAD (mRNA and protein) expression was detected in monocytes and macrophages but was not affected by P. gingivalis.
  
  
  CONCLUSIONS
  Although P. gingivalis produces a PAD that can citrullinate extracellular proteins and may contribute to the citrullinated protein load in gingival tissues, it does not appear to affect PAD expression or citrullination by host monocytes or macrophages.
authors.affiliation: School of Dentistry, Colgate Australian Clinical Dental Research Centre, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Ceilidh
authors.initials: C
authors.lastname: Marchant
authors.forename: Malcolm D
authors.initials: MD
authors.lastname: Smith
authors.forename: Susanna
authors.initials: S
authors.lastname: Proudman
authors.forename: David R
authors.initials: DR
authors.lastname: Haynes
authors.forename: P Mark
authors.initials: PM
authors.lastname: Bartold
mesh_terms: D001431:Bacteriological Techniques; D015153:Blotting, Western; D061207:Calcium Ionophores / Q000494:pharmacology; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D002956:Citrulline / Q000378:metabolism*; D003124:Colorimetry / Q000379:methods; D006801:Humans; D006867:Hydrolases / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000201:enzymology / Q000382:microbiology; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000382:microbiology*; D050296:Microbial Viability; D009000:Monocytes / Q000187:drug effects / Q000201:enzymology / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000378:metabolism*; D000080064:Protein-Arginine Deiminase Type 2; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases; D011506:Proteins / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods
chemical_list: D061207:Calcium Ionophores; D011506:Proteins; D002956:Citrulline; D015759:Ionomycin; D006867:Hydrolases; C000620352:PADI2 protein, human; C000629235:PADI4 protein, human; D000080064:Protein-Arginine Deiminase Type 2; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases