Periodontitis is a prevalent, chronic inflammatory, non-communicable disease, affecting over 50% of adults worldwide, while cardiovascular disease-related mortality accounts for 31% of all global deaths. Increasing evidence links periodontitis with cardiovascular disease. Less established is how different types of oral bacteria influence endothelial inflammation and how this contributes to atherosclerotic plaque development. This study uses both single-species planktonic-grown bacteria and multispecies biofilm fragments to examine the interaction of oral bacteria with the endothelium in vitro and assesses the resulting inflammatory responses.
Inflammatory cytokines (CXCL8, CCL2, IL-6), and the adhesion molecule VCAM-1, were investigated, as these molecules are instrumental in atherosclerosis pathogenesis. Short-term bacterial-endothelial cell interaction did not induce cell damage. Upon infection, endothelial cells displayed species-specific inflammatory responses to planktonic oral bacteria. S. mitis stimulated no immune response, P. gingivalis produced low gene responses but undetectable protein secretion due to gingipain degradation. T. forsythia and A. actinomycetemcomitans produced gene and protein responses at high MOI only. In contrast, F. polymorphum and F. nucleatum induced large gene expression and protein secretion responses in an MOI-dependent manner. Multispecies biofilm fragments bound to the endothelium and stimulated a pro-inflammatory gene response, although this did not translate into protein release due to gingipain-mediated degradation. When wild-type P. gingivalis was replaced with a gingipain-null mutant, levels of pro-inflammatory chemokines were significantly elevated. THP-1 monocytes were also shown to firmly adhere to biofilm fragment-stimulated endothelial cells.
In conclusion, oral pathobionts may play different roles when interacting with the endothelium, with Fusobacterium driving endothelial-mediated immune responses compared to other bacteria. Novel multispecies studies indicate that P. gingivalis levels in biofilm are instrumental in determining the outcome of biofilm/endothelial interactions. These data highlight the importance of studying the periodontitis-atherosclerosis link using multispecies biofilm and bring us closer to better understanding the mechanisms of periodontal-mediated systemic disease.
