Prothrombin fragments containing kringle domains induce migration and activation of human neutrophils

The cross-talk between inflammatory and coagulation cascades has been demonstrated. Prothrombin processing releases the protease domain (thrombin) along with two catalytically inactive kringle-containing derivatives: prothrombin fragments 1 (F1) and 2 (F2). It is well established that thrombin is able to trigger an inflammatory response but the possible effects of prothrombin fragments on leukocyte functions are still unknown. In this report, we demonstrate for the first time that both F1 and F2 prothrombin fragments, interfere with intracellular functional signaling pathways to modulate human neutrophil migration. In addition, we show that thrombin, fragment 1 and fragment 2 induce human neutrophil chemotaxis. The effect of fragment 2, but not fragment 1, was partially inhibited by pertussis toxin, an inhibitor of G(alphai)-signaling. The pre-treatment of cells with fragment 2 inhibited thrombin-induced chemotaxis, while both fragments impaired neutrophil migration induced by interleukin-8. F1 and F2 increased the expression and activation of G-protein-coupled receptor kinase-2, which has emerged as a key effector in the desensitization of chemokine receptors. In parallel, prothrombin fragments activated extracellular signal-regulated kinase 1/2, stimulating its phosphorylation and nuclear translocation, and induced inhibitor of kappa-B phosphorylation and degradation followed by nuclear factor-kappa B translocation to nucleus. Furthermore, both prothrombin fragments induced interleukin-8 gene expression in human neutrophils. These findings suggest that the interference with neutrophil signaling and function, caused by kringle-containing prothrombin fragments may desensitize these cells to respond to further activation by thrombin and interleukin-8 during inflammatory and coagulation responses.