Evidence That Glucose Increases Monocyte Binding to Human Aortic Endothelial Cells

The rate of atherosclerosis is accelerated in humans with diabetes. The adhesion of monocytes to the vascular endothelium is a key event in the development of atherosclerosis. Alloxan (ALX)-induced diabetes in rabbits causes leukocyte accumulation on the arterial surface. However, the effect of glucose exposure on monocyte binding is not understood. We evaluated the effect of chronic elevated glucose on human monocyte binding to human aortic endothelial cells (HAEC) in culture. Monocyte binding to HAEC was significantly increased by chronic incubation of HAEC in high glucose for 7–10 days (CH-HG; 25 mM) compared with cells cultured for the same time in normal glucose (5.5 mM; CH-HG, 188 ± 10 cells/field vs. normal glucose, 111 ± 7; P < 0.0005). Use of mannitol at a concentration to stimulate the hyperosmolar effects of glucose did not significantly alter monocyte binding. Acute 20-min exposure of HAEC to high glucose did not alter monocyte binding. The adherence of HL-60 cells, a neutrophil-like cell line, or human neutrophils was not induced by CH-HG culture. High glucose–induced monocyte binding was not associated with induction of the major endothelial cell adhesion molecules, including E-selectin, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1 (ICAM-1). A monoclonal antibody TS1–18 to the β₂ integrin component that is involved in binding to ICAM-1 on endothelial cells significantly reduced monocyte binding, whereas anti-VLA-4 antibody was not effective. These results suggest that hyperglycemia can accelerate the rate of atherosclerosis in diabetics by increasing monocyte binding to the endothelium.