Selective recruitment of neutrophils and lymphocytes by thrombin: a role for NF-kappaB

With the use of a whole blood laminar flow chamber system, we examined the types of leukocytes, adhesion molecules and the role of nuclear factor-kappaB (NF-kappaB) in thrombin-induced leukocyte recruitment. Primary human umbilical vein endothelial cells (HUVEC) stimulated with thrombin induced a significant increase in P-selectin-dependent neutrophil recruitment. Unexpectedly, brief thrombin stimulation (3 min) of endothelium also induced a significant lymphocyte recruitment 4 h later in addition to neutrophil recruitment. E-selectin antibody reduced neutrophil recruitment by >90%, whereas vascular adhesion molecule-1 (VCAM-1)/alpha4-integrin were primarily responsible for lymphocyte recruitment. To examine whether NF-kappaB contributed to leukocyte recruitment 4 h post thrombin stimulation, we treated HUVEC with the NF-kappaB inhibitor MG-132 for 1 h before thrombin stimulation. MG-132 significantly reduced the number of rolling (77.1%) and adherent (79.9%) leukocytes compared with thrombin stimulation alone. The inhibitor was more effective at preventing lymphocyte than neutrophil recruitment, consistent with its greater effect on VCAM-1 versus E-selectin expression. Tumor necrosis factor-alpha- and MG-132-treated HUVEC displayed no inhibition of leukocyte recruitment despite a decrease in NF-kappaB activation. In summary, thrombin causes predominant neutrophil recruitment via rapid P-selectin expression but also a delayed E-selectin- and VCAM-1-dependent neutrophil and lymphocyte recruitment via de novo protein synthesis. Although NF-kappaB mobilization was essential for thrombin-mediated VCAM-1-dependent recruitment, it only partially contributed to E-selectin-dependent recruitment.