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Effects of modified low density lipoprotein and hypoxia on the expression of endothelial leukocyte adhesion
1Department of Laboratory Medicine, Niigata University School of Medicine, Japan.
Objectives:
Expression of endothelial leukocyte adhesion molecule (ELAM-1 or CD62E) plays a role as an early event of atherogenesis. It is well known that interleukin-1 (IL-1) expresses ELAM-1 on vascular endothelial cells. We have examined pathological factors that induce ELAM-1 expression on cultured endothelial cells.
Methods:
Examined factors were native low density lipoprotein (LDL), oxidized LDL, glycated LDL, hypoxia, and IL-1. Peroxidation of LDL was performed by ultraviolet radiation. Hypoxia was reproduced by adding a hypoxic cell-culture medium that was deoxygenated by use of a vacuum pump and nitrogen gas. Endothelial cells were harvested from a porcine aorta and were allowed to proliferate to be subconfluent in slide chambers. Expression of ELAM-1 was evaluated by counting the number of cells that were characterized by positive staining with the immunohistochemical technique.
Results:
Without any stimulants, about 6.9% of the endothelial cells expressed ELAM-1. Weakly oxidized LDL (12 pmol/micrograms protein) significantly expressed ELAM-1 (14.8%) after an incubation period of 1 hour. Glycated LDL induced significant expressions (12.6%) in a fructosamine concentration of 65 pmol/micrograms protein. A one-hour incubation with a hypoxic culture medium expressed ELAM-1 in 16.3% of the cells. Native LDL did not cause any significant increases in the percentage. IL-1 expressed ELAM-1 in 30% of the cells even with as low a concentration as 3.1 U/ml.
Conclusions:
The present study shows that not only IL-1 but also weakly oxidized LDL, glycated LDL, and hypoxia may be possible factors that cause the expression of ELAM-1.