Study on Role of Neutrophil in Endothelial Cell Injury under High Glucose Condition

Son, Seok Man; Kim, In Ju; Kim, Yong Ki

Abstract

BACKGROUND: High glucose level plays a major role in the injury of endothelium during the early event in diabetic vascular complication. It was speculated that high glucose level may cause endothelial cell injury by neutrophil activation.
METHODS
The human umbilical vein endothelial cells (HUVEC) were obtained from American Type Culture Collection. The cells were incubated as long as 24 hours to evaluate the expression of E-selectin on the cell surface using whole cell ELISA method. The adherence of neutrophils to human umbilical endothelial cell monolayers and transendothelial migration of 51Cr-labeled neutrophils were evaluated under the condition of different concentrations of D-glucose (5.5, 15, and 30 mmol/L). L-glucose (30 mmol/L) was used as an osmotic control after 24h incubation. We also measured neutrophil-mediated endothelial cell cytotoxicity using a 51Cr-release assay and release of activating markers (lactoferrin and myeloeroxidase) from neutrophils under the same conditions.
RESULTS
The expression of E-selectin was increased on endothelium when incubated with medium containing high glucose (30 mmol/L) compared to control (5.5 mmol/L) preparation (1.36 OD vs. 0.79 OD, p<0.05). Increased adherence of neutrophils to HUVEC was observed with high glucose when compared to control (10.4% vs. 2.9%, p<0.01). Similarly, neutrophil migration across the cultured endothelial monolayers were also significantly increased by high glucose (49.8% vs. 27.3%, p<0.05). 51Cr-release from endothelial cells by neutrophils stimulated with high glucose was greater than that with control (27.5% vs. 10.6%, p<0.05). Release of activating markers from neutrophils incubated with high glucose was greater than that from neutrophils incubated with control.
CONCLUSION
These results indicate that high glucose increases the adherence and transendothelial migration of neutrophils and cause endothelial cell injury through neutrophil activation. Thus, it is concluded that high glucose level maybe contribute to manifestation of the diabetic vascular disease, including the early step in the initiation of an acute inflammation of vascular endothelial cells.