Oral Bacteria Modulate Aortic Endothelial Cell Signaling and Function

Objectives: Periodontal disease is associated with systemic conditions such as cardiovascular disease (CVD) and diabetes. Despite strong associations with CVD, there is a significant lack of knowledge of how oral bacteria modify the host endothelium, thus contributing to atherosclerosis. Cytoskeleton rearrangement is a factor in formation of atherosclerotic lesions, including recruitment and infiltration of leukocytes. Many atherosclerotic plaques demonstrate multiple oral bacteria species, including Treponema denticola. Phosphoinositide 3-kinase (PI3K) and phosphatase and tensin homolog (PTEN) are key regulators in the maintenance of healthy endothelium. T. denticola is associated with severe periodontal disease and dysregulates the PTEN:PI3K signaling axis in neutrophils. Our objective is to characterize how oral pathogens disrupt endothelial cell homeostasis, contributing to a pro-atherosclerotic environment through cell signaling modulation, cytoskeleton rearrangement and alterations in adhesion molecules.
Methods: Cultured bovine aortic endothelial cells (BAE) were exposed to T. denticola (MOI 100) for 24 hours. Cell lysates were collected to visualize protein levels of PTEN and PI3K (Western blot). RNA was collected to quantify changes in gene transcription of cell adhesion molecules such as selectins (qRT-PCR). Nuclei (DAPI) and actin (phalloidin) were visualized by confocal microscopy to show cytoskeleton rearrangements.
Results: PTEN was decreased and PI3K-alpha subunit was increased in cells cultured with bacteria compared to cells alone. Gene expression of several adhesion molecules, E-selectin and P-selectin, increase more than 10-fold. Exposure to this bacterium also leads to significant rearrangement of the cell cytoskeleton.
Conclusions: T. denticola contributes to a pro-atherosclerotic environment by modulating the PTEN:PI3K signaling mechanism and altering expression of adhesion molecules and rearrangement of the cytoskeleton. This indicates that disruption of the endothelial barrier by oral bacteria may promote an atherosclerotic environment to recruit immune cells, thus advancing disease and the local inflammatory environment.