Abstract 683: Factor Seven Activating Protease (FSAP) Expression Enhanced by Differentiation of Human Monocytes Into Macrophages and Accumulated in Coronary Atherosclerotic Plaques
FSAP is a novel plasma serin protease and it is considered to be a potent activator of factor VII as well as of single-chain plasminogen activators, and suggested to be predictor for progression of atherosclerosis. The present study was performed (i) to characterize FSAP expression in immunocompetent cells and (ii) to investigate whether FSAP is present in coronary atherosclerotic plaques and normal vessels. FSAP gene and protein expression was analyzed in stimulated (LPS, IL-1, IL-6) and un-stimulated cultured human monocytes, macrophages, dendritic cells, lymphocytes, endothelial cells and coronary smooth muscle cells with the use of real-time RT-PCR, Western blot techniques and immunoprecipitation. Directional coronary atherectomy specimens from 23 lesions were analyzed by using the immunohistochemistry, real-time RT-PCR and Western blotting. Immunocompetent cells, but not endothelial cells and coronary smooth muscle cells, were fond to express FSAP on both gene and protein levels. Macrophages presented significantly higher FSAP expression than undifferentiated monocytes. In contrast, dendritic cells, differentiated from monocytes, strongly down-regulated FSAP expression. The protease expression was biphasically affected by LPS and pro-inflammatory cytokine (IL-1, IL-6) induced a time dependent increase in expression. FSAP antigen and mRNA expression was detected in coronary atherosclerotic lesion as demonstrated by ex vivo analysis. Gene analysis showed that the FSAP gene was significantly more expressed (p < .001) and FSAP antigen had an increased positive staining both intracellularly and extracellularly (p < .004) in acute coronary syndrome cases compared with stable angina cases. FSAP accumulated focally also in lipid-rich areas within the necrotic cores of the atherosclerotic plaques of human internal mammary artery, but not in normal vessels. This is the first study to demonstrate that circulating immunocompetent cells express FSAP on both protein and mRNA level. The detection of FSAP within coronary atherosclerotic lesions identifies a so far unrecognized procoagulant mediator in the diseased coronary vessel wall and may be related to the pathogenesis of plaque vulnerability and thrombogenity.