Porphyromonas gingivalis lipopolysaccharide lipid A heterogeneity differentially modulates the expression of IL-6 and IL-8 in human gingival fibroblasts

Porphyromonas gingivalis lipopolysaccharide (LPS) displays a significant amount of structural heterogeneity, containing both tetra- (LPS(1435/1449) ) and penta-acylated (LPS(1690) ) lipid A structures. This study investigated the effects of the two isoforms of P. gingivalis LPS on the expression of IL-6, IL-8 and TNF-α in human gingival fibroblasts (HGFs).HGFs were stimulated with P. gingivalis LPS(1435/1449) and LPS(1690) in both dose- (1 ng-10 μg/ml) and time-dependent (2-48 h) experiments. Total RNA and protein were extracted and used for analysis of the IL-6, IL-8 and TNF-α transcripts as well as IL-6 and IL-8 proteins, by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.P. gingivalis LPS(1690) significantly up-regulated the mRNA and protein expression of IL-6 and IL-8, whereas P. gingivalis LPS(1435/1449) did not induce significant host response. The expression levels of IL-6 and IL-8 up-regulated by P. gingivalis LPS(1690) continuously increased with time course. In contrast, TNF-α transcript expression was up-regulated promptly by P. gingivalis LPS(1690) after 2 h of stimulation and gradually declined afterwards.This study suggests that P. gingivalis LPS heterogeneity may differentially modulate the pro-inflammatory cytokine expression in HGFs, which may contribute to periodontal pathogenesis.