The p38 mitogen-activated protein kinase pathway plays a critical role in thrombin-induced endothelial chemokine production and leukocyte recruitment

Thrombin, the terminal serine protease in the coagulation cascade, is a pro inflammatory molecule in vivo and induces endothelial activation in vitro. The cellular signaling mechanisms involved in this function are unknown. Th e role of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in thrombin-induced chemokine production was studied. Phosphorylation of b oth p38 MAPK and its substrate, ATF-2, was observed in human umbilical vein endothelial cells (HUVECs) stimulated with thrombin, with a maximum after 5 minutes of stimulation. Using the selective p38 MAPK inhibitor SB203580, there was a significant decrease in thrombin-induced interleukin-8 (IL-8) a nd monocyte chemotactic protein-1 (MCP-1) protein production and messenger RNA steady-state levels. In addition, SB203580 decreased IL-8 and MCP-1 pro duction induced by the thrombin receptor-1 agonist peptide (TRAP), suggesti ng functional links between the thrombin G protein-coupled receptor and the p38 MAPK pathway. Furthermore, endothelial activation in the presence of S B203580 decreased the chemotactic activity of thrombin-stimulated HUVEC sup ernatant on neutrophils and monocytic cells. In contrast, the p42/p44 MAPK pathway did not appear to be involved in thrombin- or TRAP-induced endothel ial chemokine production, because there was no reduction in the presence of the p42/p44-specific inhibitor PD98059. These results demonstrate that the p38 rather than p42/44 MAPK signaling pathway plays an important role in t hrombin-induced endothelial proinflammatory activation and suggest that inh ibition of p38 MAPK may be an interesting target for anti-inflammatory stra tegies in vascular diseases combining thrombosis and inflammation.