Porphyromonas gingivalis, Not P. endodontalis, Lipopolysaccharide Induces Macrophage M1 Profile

Objectives: The lipopolysaccharide (LPS) of Porphyromonas gingivalis (Pg) and P. endodontalis (Pe) are related to the etiopathogenesis of apical periodontitis. However, the immune response induced by LPS from Prophyromonas spp. specifically from Pg (Pg-LPS) and LPS from Pe (Pe-LPS), in macrophages is not fully understood. We aimed to characterize the polarization profiles of human macrophages stimulated with LPS obtained from reference strain and clinical isolates of either Pg or Pe, and a combination of both species.

Methods: THP-1 cell line (ATCC TIB-202) was differentiated to macrophages with 10 nM of phorbol 12-myristate 13-acetate (PMA) and stimulated with Pg-LPS (10 µg/mL), Pe-LPS (10 µg/mL) or both for 24 hours. Macrophages without stimulation were used as a negative control, and macrophages stimulated with LPS from Escherichia coli (Ec-LPS) O127:B8 (10 µg/mL) were used as a positive control. Then, cells were labeled with anti-CD64, anti-CD80 (M1), anti-CD163, anti-CD206 (M2) antibodies, and analyzed by flow cytometry. Moreover, we measured TNF-α, IL-1β, IL-6, IL-12 (M1) IL-10 and IL-1Ra (M2) from culture supernatant by ELISA/Multiplex.

Results: Pg-LPS decrease CD64 surface expression, increase CD80 surface expression, and increase the levels of TNF-α, IL-1β, IL-6, IL-12 (M1), and IL-10 and IL-1Ra (M2) (p<0.05) similar to Ec-LPS, but in a lower proportion. In contrast, Pe-LPS and the combination of Pg-LPS and Pe-LPS, did not induce changes on the levels of CD64, CD80 or cytokines levels.
Conclusions: Pg-LPS would be inducing a M1 profile in macrophages, unlike Pe-LPS that did not show changes on surface markers and cytokines levels.