Phagocytosis is a fundamental process in which phagocytes capture and ingest foreign particles including pathogenic bacteria. Several oral pathogens have anti-phagocytic strategies, which allow them to escape from and survive in phagocytes. Impaired bacteria phagocytosis increases inflammation and contributes to inflammatory diseases. The purpose of this study is to investigate the influences of various agents on oral pathogenic phagocytosis. To determine phagocytosis, Streptococcus mutans, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were stained with 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE), and was measured using flowcytometery and confocal microscopy. The influencing factors on phagocytosis were evaluated through the pretreatment of ROS inhibitor (N-acetyl-L-cysteine (NAC)), lysozyme, potassium chloride (KCI) and adenosine triphosphate (ATP) in THP-1 cells. Expression of pro-inflammatory cytokines was determined by enzyme-linked immunosorbent assay (ELISA). The phagocytosis of various bacteria increased in a MOI-dependent manner. Among the tested bacteria, phagocytosis of P. gingivalis showed the highest fluorescent intensity at same infection time. Among the tested inhibitors, the NAC treatment significantly inhibited phagocytosis in all tested bacteria. In addition, NAC treatment indicated a similar pattern under the confocal microscopy. Moreover, NAC treatment significantly increased the bacteriainduced secretion of IL-1β among the tested inhibitors. Taken together, we conclude that the phagocytosis occurs differently depending on each bacterium. Down-regulation by ROS production inhibited phagocytosis and lead increased of oral pathogens-associated inflammation.

Introduction
 Materials and Methods
  Bacterial culture
  Cell culture and treatment
  Phagocytosis assay
  Cytokine production analysis
  Statistics
 Results
  Phagocytosis of various oral bacteria increased in aMOI-dependent manner
  Treatment of ROS inhibitor N-acetyl-L-cysteine(NAC) significantly inhibited phagocytosis of theTHP-1 cells
  NAC treatment significantly increased the bacteriainducedsecretion of inflammatory cytokine IL-1β
 Discussion
 References

• Chung Jin(Department of Oral Microbiology, School of Dentistry, Pusan National University) Correspondence to
• Hee Sam Na(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Hyun Ah Lee(Department of Oral Microbiology, School of Dentistry, Pusan National University)
• Yuri Song(Department of Oral Microbiology, School of Dentistry, Pusan National University)