Expression of TLRs in Periodontitis tissues associated with Porphyromonas gingivalis

Toll-like receptors (TLRs) are key signal transduction elements induced by many pathogen- associated molecular patterns (PAMPs). However, the relationship between these factors and periodontopathic bacteria in periodontal tissue has not been investigated. Objectives: This study aimed to compare the levels of TLR2, TLR4 and TLR9 mRNA in chronic periodontitis tissues to those in healthy control tissues and to study the relationship between these molecules and periodontal pathogens. Methods: Gingival tissue and subgingival plaque samples were collected from 21 chronic periodontitis and 16 periodontally healthy sites. RNA was extracted from the tissue and subjected to RT-PCR using primers specific for TLR2, TLR4 or TLR9. Beta actin was amplified as a control to ensure equal loading. The intensity of RT-PCR products was analyzed by a densitometer in proportion to the intensity of the beta actin. The numbers of Porphyromonas gingivalis (Pg) and Actinobacillus actinomycetemcomitans (Aa) were determined by quantitative real-time PCR. Results: Our results demonstrated significant differences in the mRNA expression levels of TLR2 and TLR9, but not TLR4, in chronic periodontitis tissues compared to healthy controls (p<0.01 and p<0.05, respectively). In addition, the expression levels of TLR2 and TLR9, but not TLR4, were significantly correlated with increased numbers of Pg. Aa was detected in less than 10% of all sites. Conclusions: These data demonstrated for the first time an association between upregulated TLR2 and TLR9 levels and the number of Pg in clinically obtained periodontal tissues, suggesting an important role of these two molecules in the periodontal inflammatory process. This study was supported by the National Research Council of Thailand and Japan Society for the Promotion of Science.