P. gingivalis Lipopolysaccharide with different structures differentially modulates innate responses

Objectives: P. gingivalis Lipopolysaccharide (LPS) contains both tetra- and penta-acylated lipid A structures, which show opposing effects on E-selectin expression in human endothelial cells. This study was to determine whether different lipid A structures of P. gingivalis LPS differentially modulate host innate responses in gingival epithelium. Methods: Reconstituted human gingival epithelia (RHGE) were incubated with P. gingivalis LPS1690, P. gingivalis LPS1435, and E. coli LPS in various concentrations ranging from 1 ng/ml to 10 μg/ml. The expression of human b-defensins (hBD) 1-3, CD14, TLR-2, TLR-4, TLR-6, MD-2 and MyD88 mRNAs in RHGE was detected by RT-PCR. hBD-2 peptide was detected by immunohistochemistry and ELISA. Results: hBD-2 mRNA expression was significantly upregulated by low doses of E. coli LPS and high doses of P. gingivalis LPS1690, whereas hBD-2 peptide was not upregulated accordingly by P. gingivalis LPS1690. Both hBD-2 mRNA and peptide were downregulated by all doses of P. gingivalis LPS1435. The expression of CD14, TLR-2, TLR-4, TLR-6 and MD-2 mRNAs was also differentially regulated by the two forms of P. gingivalis LPS. Conclusions: P. gingivalis LPS with different lipid A structures may differentially modulate host innate responses in gingival epithelium, which may represent a novel pathogenic mechanism of P. gingivalis in bacteria-host interactions. Supported by the Hong Kong Research Grants Council (CERG 7518/05M to LJJ).