RAPID COMMUNICATION Fluid Shear Stress Modulates Surface Expression of Adhesion Molecules

We investigated the effect of hemodynamic shear forces on the expression of adhesive molecules, E-selectin, and intercellular adhesion molecule-l (ICAM-1) on human umbilical vein endothelial cells (HUVEC) exposed t o laminar (8 dynes/ cmz) or turbulent shear stress 18.6 dyneslcrn' average), or to a static condition. Laminar flow induced a significant timedependent increase in the surface expression of ICAM-1, as documented by flow cytometry studies. Endothelial cell surface expression of CAM-1 in supernatants of HUVEC exposed t o laminar flow was not modified, excluding the possibility that HUVEC exposed t o laminar flow synthetize factors that upregulate ICAM-1. The effect of laminar flow was specific for ICAM-1, while E-selectin expression was not modulated by the flow condition. Turbulent flow did not affect surface expression of either E-selectin or ICAM-1. To evaluate the functional significance of the laminar-flow-induced increase in ICAM-1 expression, we studied the dynamic interaction of total leukocyte suspension with HUVEC ex-