Enhancement of Porphyromonas gingivalis-Lipopolysaccharide Induced MCP-1 Expression by High Glucose in Human Endothelial Cells

Abstract

To investigate the synergistic effects of periodontal disease and diabetes mellitus on atherosclerosis, we evaluated the monocyte chemoattractant protein-1 (MCP-1) expression of endothelial cells induced by Porphyromonas gingivalis-lipopolysaccharide (LPS) and high glucose. We also tested whether antioxidants could inhibit the MCP-1 expression induced by the simultaneous stimulation of LPS and high glucose. Human umbilical vein endothelial cells (HUVECs) were stimulated with various concentrations of P. gingivalis-LPS (0.1, 1.0, and 10 µg/mL) in normal glucose (5.5 mM), with high glucose (10 mM and 20 mM), and with 0.1 µg/mL P. gingivalis-LPS in high glucose. MCP-1 expressions were measured by realtime RT-PCR and ELISA. Vitamin C (100 µM) and vitamin E (50 µM) were administered before simultaneous stimulation with 0.1 µg/mL P. gingivalis-LPS and 20 mM glucose. LPS ≥ 1.0 μg/mL increased the expression of MCP-1 mRNA and protein compared to unstimulated HUVECs. High glucose in the culture medium increased the MCP-1 mRNA expression slightly but significantly at 2 hr of incubation, but the MCP-1 protein level was not increased. Simultaneous stimulation with 0.1 μg/mL LPS and high glucose increased the expression of MCP-1 mRNA and protein compared to unstimulated HUVECs. By contrast, pre-incubation of vitamin C or E inhibited the increase of MCP-1 mRNA expression induced by 0.1 μg/mL LPS and 20 mM glucose. Our finding that high glucose enhanced the MCP-1 expression with even a low level of LPS suggests that caution is advisable regarding the atherogenicity of diabetic patients with periodontal disease.