Effect of Oxidized LDL on Neutrophil Adhesion and Transendothelial Migration

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

Abstract

BACKGROUND: It is well recognized that oxidized low density lipoproteins (ox-LDL) play a critical role in the pathogenesis of atherosclerosis. The activation of circulating leukocytes and their adhesion to the vascular endothelium in response to acute stimuli characterize the first step in initiation of an acute inflammatory response. Through the action of degranulation products, adherent leukocytes induce vascular hyperpermeability and contribute to vascular injury. So, we have investigated the neutrophil adhesion to vascular endothelium, a constant feature of early atherogenesis and transendothelial migration of neutrophil induced by ox-LDL. METHOD: In a series of experiments, human umbilical vascular endothelial cells (HUVECs) were incubated for 24 h after addition of native human LDL (100 ug/mL) and of ox-LDL (100 ug/mL) to the medium. The adherence of 51Cr-labeled neutrophils to endothelial monolayers was measured by neutrophil adhesion assay. For diapedesis experiments, HUVECs were grown to confluence on 8.0um pore cell culture inserts. 51Cr-labeled neutrophils were added to the apical surface of HUVEC monolayers and allowed to migrate into the lower chamber for 3 h under the same preparations of native and oxidized LDLs. Reaults: The secretion of IL-8 depended on the concentration of IL-1a and LPS used to stimulate endothelial monolayers in vitro. In addition, ox-LDL triggered secretion of IL-8 from cultured HUVECs compared to that of n-LDL (867.6 pg/mL vs. 273.1 pg/mL, p<0.01). Increased adherence of neutrophils to HUVECs vs observed with ox-LDL preparation compared to native LDL preparation (36.8+1.5% vs. 25.9+1.7%, p<0.05). Similarly, neutrophil migration across cultured endothelial monolayers was also significantly increased by ox-LDL (48.7+3.8% vs. 34.4+2.9%, p<0.05).
CONCLUSION
These results show that ox-LD1. can induce increased neutrophil adhesion and migration through IL-8, a potent effector of neutophil functions, secreted by stimulated endothelial cells. So, we suggest that ox-LDL may affect many components of the atherogenic process, including the early step in the initiation of m acute inflammation of vascular endothelial cells.