title: N-acetylcysteine and the human serum components that inhibit bacterial invasion of gingival epithelial cells prevent experimental periodontitis in mice.
abstract: OBJECTIVE
  We previously reported that human serum significantly reduces the invasion of various oral bacterial species into gingival epithelial cells in vitro. The aims of the present study were to characterize the serum component(s) responsible for the inhibition of bacterial invasion of epithelial cells and to examine their effect on periodontitis induced in mice.
  
  
  METHODS
  Immortalized human gingival epithelial (HOK-16B) cells were infected with various 5- (and 6-) carboxy-fluorescein diacetate succinimidyl ester-labeled oral bacteria, including Fusobacterium nucleatum, Provetella intermedia, Porphyromonas gingivalis, and Treponiema denticola, in the absence or presence of three major serum components (human serum albumin [HSA], pooled human IgG [phIgG] and α1-antitrypsin). Bacterial adhesion and invasion were determined by flow cytometry. The levels of intracellular reactive oxygen species (ROS) and activation of small GTPases were examined. Experimental periodontitis was induced by oral inoculation of P. gingivalis and T. denticola in Balb/c mice.
  
  
  RESULTS
  HSA and phIgG, but not α1-antitrypsin, efficiently inhibited the invasion of various oral bacterial species into HOK-16B cells. HSA but not phIgG decreased the adhesion of F. nucleatum onto host cells and the levels of intracellular ROS in HOK-16B cells. N-acetylcysteine (NAC), a ROS scavenger, decreased both the levels of intracellular ROS and invasion of F. nucleatum into HOK-16B cells, confirming the role of ROS in bacterial invasion. Infection with F. nucleatum activated Rac1, a regulator of actin cytoskeleton dynamics. Not only HSA and NAC but also phIgG decreased the F. nucleatum-induced activation of Rac1. Furthermore, both HSA plus phIgG and NAC significantly reduced the alveolar bone loss in the experimental periodontitis induced by P. gingivalis and T. denticola in mice.
  
  
  CONCLUSIONS
  NAC and the serum components HSA and phIgG, which inhibit bacterial invasion of oral epithelial cells in vitro, can successfully prevent experimental periodontitis.
authors.affiliation: Department of Oral Microbiology and Immunology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
authors.forename: Jehan
authors.identifier: 0000-0001-5658-4736
authors.initials: J
authors.lastname: Alam
authors.affiliation: Department of Oral Microbiology and Immunology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
authors.forename: Keum Jin
authors.identifier: 0000-0002-4849-0083
authors.initials: KJ
authors.lastname: Baek
authors.affiliation: Department of Oral Microbiology and Immunology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
authors.forename: Yun Sik
authors.identifier: 0000-0002-1321-8119
authors.initials: YS
authors.lastname: Choi
authors.affiliation: Department of Oral Microbiology and Immunology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
authors.forename: Yong Cheol
authors.identifier: 0000-0002-2124-427X
authors.initials: YC
authors.lastname: Kim
authors.affiliation: Department of Oral Microbiology and Immunology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
authors.forename: Youngnim
authors.identifier: 0000-0002-6496-5560
authors.initials: Y
authors.lastname: Choi
keywords: Albumins; Bacteria; Epithelial cells; Immunoglobulin G; Periodontitis