Porphyromonas gingivalis-induced inflammatory responses in THP1 cells are altered by native and modified low-density lipoproteins in a strain-dependent manner.

Strong epidemiological evidence supports an association between cardiovascular and periodontal disease and furthermore, the periodontopathogen Porphyromonas gingivalis has been identified in blood and from atheromatous plaques. Blood exposed to P. gingivalis shows an increased protein modification of low-density lipoprotein (LDL). In this study, we investigate the inflammatory responses of THP1 cells incubated with P. gingivalis and the effects of native or modified LDL on these responses. Reactive oxygen species (ROS) and IL-1β were observed in THP1 cells following infection with P. gingivalis ATCC33277 and W50. Caspase 1 activity was quantified in THP1 cells and correlated with IL-1β accumulation. Oxidized LDL (oxLDL) induced IL-1β release and CD36 expression on THP1 cells. Modified LDL co-stimulated with ATCC33277 exhibited regulatory effects on caspase 1 activity, IL-1β release and CD36 expression in THP1 cells, whereas W50 induced more modest responses in THP1 cells. In summary, we show that P. gingivalis is capable of inducing pro-inflammatory responses in THP1 cells, and native and modified LDL could alter these responses in a dose- and strain-dependent manner. Strain-dependent differences in THP1 cell responses could be due to the effect of P. gingivalis proteases, presence or absence of capsule and proteolytic transformation of native and modified LDL.