Combinations of Hydrostatic Pressure and Shear Stress Time-dependently Decrease E-selectin, VCAM-1 and ICAM-1 Expression Induced by Tumor Necrosis Factor-Alpha in Cultured Endothelial Cells

Abstract

Endothelial cells (ECs) are constantly subjected to shear stress, a tangential stress generated by blood flow, and hydrostatic pressure, a normal stress generated by blood pressure. Using a perfusion system that enables the independent control of flow volume and pressure, we investigated the effect of this combined stress on adhesion molecule expression in cytokine-stimulated cultured ECs. Human umbilical vein endothelial cells were incubated with 25 ng/ml tumor necrosis factor-alpha (TNF-α) for 6 hours. Activated ECs were then exposed to pulsatile flow (a shear stress of 1.5 ± 0.3 Pa, and a hydrostatic pressure of 100 ± 20 mmHg) for 1-24 hours. After exposure to pulsatile flow, endothelial selectin (E-selectin), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) were stained and observed using fluorescence microscopy. Results showed that E-selectin was expressed in approximately 30% of the total ECs after incubation with TNF-α, however, TNF-α-induced E-selectin expression was decreased after 1 hour of exposure to pulsatile flow resulting in E-selectin expression in under 10% of total ECs at 24 hours. VCAM-1 was expressed in approximately 75% of the total ECs after incubation with TNF-α, however, TNF-α-induced VCAM-1 expression was decreased after 6 hours of exposure to pulsatile flow resulting in VCAM-1 expression in approximately 40% of the total ECs at 24 hours. ICAM-1 was expressed in all ECs after incubation with TNF-α, however, TNF-α-induced ICAM-1 expression was decreased after 12 hours of exposure to pulsatile flow resulting in ICAM-1 expression in approximately 40% of the total ECs at 24 hours. These results suggest that combined stress time-dependently suppresses overexpression of cytokine-induced adhesion molecules in ECs.