title: Intragingival injection of Porphyromonas gingivalis-derived lipopolysaccharide induces a transient increase in gingival tumour necrosis factor-α, but not interleukin-6, in anaesthetised rats.
abstract: This study used in vivo microdialysis to examine the effects of intragingival application of lipopolysaccharide (LPS) derived from Porphyromonas gingivalis (Pg-LPS) on gingival tumour necrosis factor (TNF)-α and interleukin (IL)-6 levels in rats. A microdialysis probe with an injection needle attached to the surface of the dialysis membrane was implanted into the gingiva of the upper incisor. For comparison, the effects of LPS derived from Escherichia coli (Ec-LPS) on IL-6 and TNF-α levels were also analysed. Pg-LPS (1 μg/1 μL) or Ec-LPS (1 or 6 μg/1 μL) was applied by microsyringe, with gingival dialysates collected every hour. Enzyme-linked immunosorbent assay (ELISA) revealed that gingival dialysates contained approximately 389 pg·mL⁻¹ of IL-6 basally; basal TNF-α levels were lower than the detection limit of the ELISA. Pg-LPS failed to alter IL-6 levels but markedly increased TNF-α levels, which remained elevated for 2 h after treatment. Neither IL-6 nor TNF-α were affected by Ec-LPS. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed that the gingiva expresses Toll-like receptor (TLR) 2 and TLR4 mRNA. Immunohistochemical examination showed that TLR2 and TLR4 are expressed by gingival epithelial cells. The present study provides in vivo evidence that locally applied Pg-LPS, but not Ec-LPS, into the gingiva transiently increases gingival TNF-α without affecting IL-6. The present results suggest that TLR2 but not TLR4 expressed on gingival epithelial cells may mediate the Pg-LPS-induced increase in gingival TNF-α in rats.
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Taguchi
authors.affiliation: Department of Pharmacology, Nihon University School of Dentistry at Matsudo, Chiba, Japan.|Department of Pharmacology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Aono
authors.affiliation: Department of Oral Health Sciences, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawato
authors.affiliation: Department of Pathology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Masatake
authors.initials: M
authors.lastname: Asano
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
authors.affiliation: Department of Pharmacology, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Saigusa
mesh_terms: D000818:Animals; D005881:Gingiva / Q000187:drug effects* / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D008297:Male; D016966:Porphyromonas gingivalis / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D015850:Interleukin-6; D008070:Lipopolysaccharides; D012333:RNA, Messenger; C495343:Tlr2 protein, rat; C495347:Tlr4 protein, rat; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha