Porphyromonas gingivalis infection enhances Th17 responses for development of atherosclerosis

Porphyromonas gingivalis has been shown to associate with the development of atherosclerosis. Recent studies indicate that IL-17-producing T helper 17 (Th17) cells have been correlated with the emergence of atherosclerosis. Therefore, we investigated whether the Th17 cell response and expression of Th17-related molecules, in contrast with Th1- and Treg cells, are enhanced by P. gingivalis-challenge in Apolipoprotein E knockout (ApoE KO) mice.

Five mice were intravenously injected with P. gingivalis three times a week for 3 weeks and killed at 15 weeks of age. The proximal aorta lesion area, flow cytometry analysis and IL-17, IL-10, IFN-γ, and IL-1β levels in splenic cultures, and expression of Th17-related molecules in spleen and hearts were examined.

P. gingivalis-challenge showed notable accumulation of atherosclerotic plaques by Oil Red O-staining in ApoE KO mice. Intracellular cytokine staining revealed that significantly elevated CD4(+) interleukin (IL)-17A(+) T cells and slightly increased CD4(+) Foxp3(+) T cells was recognized in spleen cells of P. gingivalis-challenged mice compared with those from non-infected mice. P. gingivalis-challenge significantly increased IL-17 and IL-1β production and RORγt expression in splenic cells. Furthermore, the expression of Th17-related genes such as IL-6, TGF-β, RORγt and STAT3 were elevated in splenic cells as well as heart tissue of P. gingivalis-challenged mice.

These results suggest that P. gingivalis infection may enhance pro-inflammatory Th17 cell responses in lesion areas and spleen, thereby accelerating atherosclerosis.