Gene Expression Profiles in P. gingivalis LPS-treated Human Macrophages

Objective: Recent epidemiological studies have suggested that patients with periodontal diseases may have an increased risk of developing cardiovascular disease (CVD). This relationship could be mediated by inflammatory responses induced by products from periodontal bacterial pathogens, such as lipopolysaccharide (LPS). In order to clarify the possible mechanisms underlying this association, we analyzed the gene expression changes in human THP-1 macrophages treated with LPS from Porphyromonas gingivalis (P. gingivalis ) by microarray analysis.

Methods: Phorbol 12-myristate 13-acetate differentiated (30ng/mL, 30hrs) human THP-1 macrophages were stimulated by P. gingivalis (ATCC 33277) LPS for 2 and 6hrs. mRNA was extracted and purified from the cells, and the gene expression profile was analyzed by using Affymetrix GeneChip Human Genome Focus Arrays (approximately 8,500 genes).

Results: The expression levels of 160 genes were significantly altered by LPS treatment, when compared with untreated controls. Among these genes, after 2hrs incubation, inflammatory cytokines genes (e.g. TNF-α and IL-1β) were markedly upregulated. After 6hrs incubation, several genes of MMP implicated in atheromatous plaque rupture, were markedly upregulated. In addition, we also noticed upregulation of LOX1 genes, an oxidized LDL receptor involved in atherogenesis.

Conclusion: These results suggest that P. gingivalis LPS activates macrophages by increasing the mRNA expression levels of inflammatory cytokines, MMPs and LOX1 genes implicated in CVD. Temporal changes in mRNA expression vary for individual genes. Further work remains to elucidate the reasons why these responses vary over time.