Smoking modulates human coronary artery endothelial cell response to P.gingivalis

Cigarette smoking is well known as a strong common risk factor of periodontitis and atherosclerosis. To the best of our knowledge, no previous studies have assessed the role of smoking and periodontal infection in atherosclerosis. Objectives: In this study, we used an in vitro model of human coronary artery endothelial cell (HCAEC) culture to investigate the immune modulating effect of cigarette smoke extract(CSE) on the response of HCAECs to a Toll-like receptor(TLR) 2 ligand-Porphyromonas gingivalis lipopolysaccharide(LPS) as assessed by measurement of interleukin (IL-8) and monocyte chemoattractant protein-1 ( MCP-1) production. Methods: TLR expression of HCACEs was analyzed by RT-PCR. The responses of HCAECs to specific-purified TLR ligand and/or tumor necrosis factor-alpha were measured by IL-8 and MCP-1 production using ELISA. The effect of CSE on stimulated HCAECs was also evaluated. Results: HCAECs expressed mRNA of TLRs 1, 2, 3, 4, 5, 6, 9 and 10, but not of TLRs 7 or 8. Stimulation of HCAECs with highly purified TLR 2, 3, 4, 5 ligands led to IL-8 and MCP-1 production. Enhancement of IL-8 was observed in HCAECs after combined stimulation with P. gingivalis LPS and tumor necrosis factor-alpha, as compared with single stimulation, but the effect on MCP-1 production was minimal. CSE alone stimulated IL-8 response, whereas suppressed MCP-1 response in HCAECs. However, CSE markedly inhibited P.gingivalis-induced IL-8 and MCP-1 production. Conclusion: HCAECs expressed functional TLRs. Our results indicated that instead of enhancing cytokine response, the combination of CSE and P.gingivalis LPS suppressed IL-8 and MCP-1 production from HCAECs. However, it is interesting that CSE alone could promote HCAEC response by increasing IL-8 production. Such complex interaction between P. gingivalis LPS, CSE and the HCAEC response, which links between periodontitis, smoking, and atherosclerosis, needs further investigation.