Abstract 1358: Membrane-Type Serine Protease-1/ Matriptase Induces IL-6, IL-8 and MCP-1 in Endothelial Cells by Activation of Protease Activated Receptor-2: Potential Implications in Atherosclerosis
Background: MT-SP1, a type II transmembrane serine protease also known as matriptase, plays an important role in cell migration and matrix degradation and, thereby, may contribute to tumor cell metastasis. Hepatocyte growth factor (HGF), single-chain urokinase-type plasminogen activator (sc-uPA) and protease-activated receptor 2 (PAR-2) have been identified as in vitro substrates of MT-SP1/matriptase. Since PAR-2 is expressed in endothelial cells and contributes to inflammatory processes, we sought to investigate the effects of MT-SP1/ matriptase on cytokine expression in endothelial cells. In addition, we analyzed MT-SP1/ matriptase expression in vascular cells and atherosclerotic lesions.
Methods and Results: In endothelial cells recombinant soluble MT-SP1/matriptase dose-dependently induced interleukin (IL)-8, IL-6 and monocyte chemoattractant (MCP)-1 mRNA expression and protein release. The proteolytic activity of MT-SP1/matriptase was required, since a catalytic inactive mutant of MT-SP1/matriptase failed to alter cytokine release. MT-SP1/matriptase time-dependently induced phosphorylation of MAPK p38 and p42/44. Inhibitor experiments showed that activation of MAPK p38 and PKCα was necessary for IL-8 induction. Gene silencing of PAR-2, but not of PAR-1, abolished MT-SP1/matriptase-induced cytokine expression. In addition, overexpression of PAR-2 augmented MT-SP1/matriptase-induced IL-8 gene expression as evidence for exclusive PAR-2-signaling. In human atherectomy samples enhanced expression of MT-SP1/matriptase was found mainly in blood cells adherent to the endothelium. Similarly, MT-SP1/matriptase expression was only detected in isolated monocytes, but not in cultured endothelial or smooth muscle cells.
Conclusion: MT-SP1/matriptase induces release of proinflammatory cytokines in endothelial cells through activation of PAR-2. Interaction of monocytic MT-SP1/matriptase with endothelial PAR-2 may enhance local inflammatory changes within atherosclerotic lesions.