P. gingivalis LPS modulates hBD-2 expression through TLR2 and 4

Abstract

Objectives: P. gingivalis LPS is strongly involved in the pathogenesis of chronic periodontitis, and it displays a significant amount of lipid A structural heterogeneity with opposing inflammatory effects. This study was to examine the involvements of pattern recognition receptors in the modulation of two isoforms of P. gingivalis LPS on the expression of human b-defensin (hBD)-2 in reconstituted human gingival epithelia (RHGE).

Methods: P. gingivalis LPS1435/1449 and LPS1690 were isolated from P. gingivalis ATCC 33277 and purified with the protein contamination < 0.1%. RHGE were incubated with the two isoforms of P. gingivalis LPS and E. coli LPS (055:B5, Sigma) in both concentration- and time-dependent assays. For blocking assay, RHGE were pre-incubated for 1 h with anti-human TLR2/4 and CD14 monoclonal antibodies. RHGE were then harvested for protein assay by immunohistochemistry and ELISA, and for detection of the target mRNAs by RT-PCR/real-time PCR, respectively.

Results: hBD-2 peptide was basally detected in the upper and middle layers of control RHGE. hBD-2 mRNA was significantly upregulated by P. gingivalis LPS1690, whereas downregulated by P. gingivalis LPS1435/1449. Its peptide was significantly downregulated by P. gingivalis LPS1435/1449, but not affected by P. gingivalis LPS1690.

TLR2 and CD14 mRNAs were differentially regulated by P. gingivalis LPS as well. Pre-incubation of RHGE cultures with TLR4 or both TLR2 and TLR4 antibodies significantly blocked the P. gingivalis LPS1435/1449-induced downregulation of hBD-2 mRNA expression, whereas TLR4, CD14, or both TLR2 and TLR4 antibodies significantly blocked the P. gingivalis LPS1690-induced upregulation of hBD-2 mRNA expression.

Conclusions: This study suggests that P. gingivalis LPS with different lipid A structures could differentially modulate the expression of hBD-2 in human gingival epithelia, which may represent a novel pathogenic mechanism of P. gingivalis in periodontal pathogenesis. Supported by the Hong Kong Research Grants Council (CERG 7518/05M to LJ JIN, ljjin@hku.hk).