Porphyromonas gingivalis Alters Nrf2-PhaseII Enzymes and Nitric Oxide in Primary Human Aortic Endothelial Cells

Objectives: Periodontal disease (PD) is known to be associated with endothelial dysfunction in patients with coronary artery and/or cardiovascular disease. Vascular endothelium serves as an effective immune defensive system against periodontal pathogens. Studies have shown that Porphyromonas gingivalis actively spreads into the systemic circulation and disrupts the endothelium in periodontitis patients. Altered nitric oxide (NO) synthesis tetrahydrobiopterin (BH₄), a cofactor for nitric oxide synthases (NOS), and reduced antioxidants have long been known to be associated with vascular dysfunction and gastrointestinal motility disorders. In this study, we sought to investigate if infection with P. gingivalis alters glycogen synthase kinase 3 beta (GSK3β)/ Nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/BH₄/NOS expression in primary human aortic endothelial cells (pHAEC).
Methods: pHAE Cells were infected in vitro in the presence or absence of with P. gingivalis (strain W83, 10⁹ MOI) between 12 to 48 hour time points by adopting co-culture methods. Cell invasion and mRNA levels were evaluated by using standardized protocols, ANOVA (*p<0.05).
Results: P. gingivalis impairs endothelial cell proliferation, function, and migration 12 hr post infection. P. gingivalis infection reduced mRNA expression levels of endothelial nitric oxide synthase (eNOS), Nrf2 and heme oxygenase-1 (HO-1) in a time dependent manner. Interestingly, inducible nitric oxide synthase (iNOS) mRNA levels first showed a significant increase at 12 and 24 hr and reduced significantly at later time points. This phenomenon was correlated with changes in NO release in the media indicating anti-inflammatory defense mechanism at early stages of invasion. BH₄ (cofactor of eNOS) biosynthesis enzyme DHFR (salvage pathway) mRNA levels showed a significant decrease while mRNA levels of GSK-3β were elevated.
Conclusions:
The above suggest that periodontal bacterial infection can cause significant changes in the vascular GSK3β/BH₄/eNOS/Nrf2 pathways, which might lead to impaired vascular relaxation. Greater understanding about the factors that are adversely affecting endothelial cell function is essential for the development of new therapeutic compounds to treat PD induced vascular diseases.