Differences in the effects of cytokines on the expression of adhesion molecules in endothelial cells

Expressions of adhesion molecules on arterial endothelial cells are crucial events in initiation of atherosclerosis. Our recent study has shown that endothelial cells express endothelial leukocyte adhesion molecule-1 (ELAM-1) significantly due to stimulation with oxidized LDL, H2O2, or hypoxia. This current study is aimed at investigating temporal relations of the induction of ELAM-1, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in cultured endothelial cells of the human thoracic aorta.

The activators examined were interleukin 1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF alpha), and interferon gamma (IFN gamma). Cells were incubated with each of the cytokines at 10 ng/ml for 0.5-48 hours. The adhesion molecules were determined by enzyme immunoassay.

ELAM-1 appeared after stimulations by IL-1 and TNF alpha; ELAM-1 was induced by IL-1 after one hour, while it rose sharply after a 30-min stimulation by TNF alpha. The ICAM-1 expression was observed even in non-stimulated cells and further increased in proportion to duration of stimulation. No significant difference occurred between the effects of IL-1 and TNF alpha on the ICAM-1 expression. Weak expression of VCAM-1 was observed only by TNF alpha after 4-through 24-h stimulation. IFN gamma did not cause any changes in the expression of ELAM-1, VCAM-1, and ICAM-1.

The present data indicate a specific time course for each induction of ELAM-1 and VCAM-1, but not ICAM-1. Therefore, the combination of molecules may play a role for endothelial cells to discriminate monocytes from such other cells as neutrophils and lymphocytes.