Macrophage Activation Impacts Responses to Porphyromonas Gingivalis and its OMVs.

Objectives: Periodontal disease is a chronic oral inflammatory disease of the oral cavity. Porphyromonas gingivalis is linked to this disease and produces outer membrane vesicles (OMVs). Macrophages (MΦ) infiltrate periodontal tissues during disease and exist at these sites in different activation states; however, it is incompletely understood how MΦ activation impacts the host response to P. gingivalis. Sphingolipids (SLs) produced by P. gingivalis present on the bacterium and its OMVs modulate the host’s inflammatory response. The objective of this study was to begin to characterize the response of MΦ poised in different activation states to wild-type (WT) and SL-deficient P. gingivalis and its OMV.
Methods: Human macrophage-like THP-1 cells were treated for 24 hrs. to drive activation to classically activated (M1; TNF-α and LPS) and alternatively activated (M2; IL-4) states. Untreated THP-1 cells served as the non-activated group (M0). Activated MΦ were exposed to WT P. gingivalis and its SL-deficient mutant (MOI 100) or OMVs purified from these strains (1000 particles/cell) and samples were collected temporally up to 24 hrs. Luminex-based immunoassays measured levels of cytokine production (TNF-α, IL-6, IL-8, IL-10, and CCL5/RANTES).
Results: Luminex results showed a trend for increased cytokine production for M1 MΦ compared to M2 and M0 MΦ for both WT and SL-deficient mutant P. gingivalis. Luminex results also showed a trend for increased cytokine production for the SL-deficient mutant in comparison to the WT. These patterns were also observed with OMVs from these strains.
Conclusions: Our preliminary data support that MΦ poised in different activation states respond differently to P. gingivalis and its OMVs. It is also shown that there is a difference in the cytokine production responses to WT versus the SL-deficient mutant P. gingivalis. Further testing is needed to understand how these data may impact the progression of periodontal disease.