Porphyromonas gingivalis LPS modulates innate response of gingival epithelia

Abstract

Objective: Porphyromonas gingivalis lipopolysaccharide (PgLPS) is a crucial virulence factor strongly involved in chronic periodontitis. It is known to contain both tetra- (Pg LPS1435) and penta-acylated (PgLPS 1690) lipid A structures with opposing effects. The present study examined the effect of two isoforms of PgLPS on human gingival epithelia. Methods: Reconstituted human gingival epithelia (RHGE) were challenged with two isoforms of PgLPS together with E. coli LPS as the positive control. mRNA and proteins were harvested from tissues and culture supernatants were collected. Expression of pro- and anti-inflammatory cytokines was evaluated by Q-PCR and ELISA. Pattern recognition receptors and the relevant signaling pathways were analyzed by Q-PCR and western blot. RHGE was then blocked for CD14 and TLR2/4 and followed by PgLPS stimulation. The effects on cytokine expression were evaluated by Q-PCR and ELISA. A “tissue proteomics” approach was used to study the differential proteomic expression profiles in gingival epithelia upon Pg LPS stimulation. Results: Penta-acylated PgLPS1690 significantly upregulated the secretion of IL-1, IL-6, IL-8 and TNF-alpha in RHGE compared to PgLPS1435. Regulation of most pro-inflammatory cytokine expression by PgLPS1690 was mediated through TLR2/CD14/NF-kB axis. Differential protein profiles in RHGE were induced with the two isoforms of Pg LPS. Conclusion: P. gingivalis LPS heterogeneity differentially modulates the host innate immune response in human gingival epithelia, which may explain the niche-specific pathogenic mechanism of Porphyromonas gingivalis (Supported by GRF HKU766909M to LJJ).