Endothelial expression of ICAM is stimulated by both laminar and turbulent flow

Abstract

Hemodynamic forces such as shear stress play a role in atherosclerosis. Plaque localizes in vivo to areas exposed to turbulent flow, whereas areas exposed to laminar flow remain lesion-free. Cell adhesion molecules such as Intercellular Adhesion Molecule (ICAM) may play a role in plaque formation and are regulated by flow. Therefore we studied the differential effects of turbulent and laminar flow on ICAM expression. Human umbilical vein endothelial cells were differentially seeded and exposed to laminar flow (parallel plate, 4 or 11 dyn/cm 2) or turbulent flow (orbital shaker, 210 rpm; center, 4 dyn/cm 2; periphery, 11 dyn/cm 2) for 6 h. ICAM expression was determined by FACS analysis. ICAM expression in endothelial cells was uniformly induced, whether in the center or periphery exposed to turbulent flow ( n = 6, P = 0.3163, paired t-test) or with exposure to laminar flow at either 4 or 11 dyn/cm 2 ( n = 3, P = 0.3734, paired t-test). Laminar and turbulent flow induce ICAM expression in endothelial cells; however, the degree of induction appears similar with both laminar and turbulent flow. These results suggest that the intracellular pathways stimulated within endothelial cells by exposure to laminar or turbulent flow are either similar or converge downstream. In addition, ICAM expression may be involved in phases of plaque formation that may not be regulated by flow.