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

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-kapp aB (NF-kappaB) in thrombin-induced leukocyte recruitment. Primary human umb ilical vein endothelial cells (HUVEC) stimulated with thrombin induced a si gnificant increase in P-selectin-dependent neutrophil recruitment. Unexpect edly, brief thrombin stimulation (3 min) of endothelium also induced a sign ificant lymphocyte recruitment 4 h later in addition to neutrophil recruitm ent. E-selectin antibody reduced neutrophil recruitment by >90%, whereas va scular adhesion molecule-1 (VCAM-1)/alpha (4)-integrin were primarily respo nsible for lymphocyte recruitment. To examine whether NF-kappaB contributed to leukocyte recruitment 4 h post thrombin stimulation, we treated HUVEC w ith 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 mo re effective at preventing lymphocyte than neutrophil recruitment, consiste nt with its greater effect on VCAM-1 versus E-selectin expression. Tumor ne crosis factor-alpha- and MG-132-treated HUVEC displayed no inhibition of le ukocyte recruitment despite a decrease in NF-kappaB activation. In summary, thrombin causes predominant neutrophil recruitment via rapid P-selectin ex pression but also a delayed E-selectin- and VCAM-1-dependent neutrophil and lymphocyte recruitment via de novo protein synthesis. Although NF-kappaB m obilization was essential for thrombin-mediated VCAM-1-dependent recruitmen t, it only partially contributed to E-selectin- dependent recruitment.