The Roles Of Fibrin Fibrinogen Degradation Products In Macrophage-derived Foam Cells

Atherosclerosis is a chronic inflammatory disease. This widely accepted concept is based on a body of evidence from experimental and human observational studies, which is defined as macrophages and lymphocytes to 'invading' pathogenic lipoproteins in the arterial wall. Macrophages thus have essential functions in all phases of atherosclerosis, from development of the fatty streak to processes that ultimately contribute to plaque rupture and myocardial infarction.A large number of clinical studies in different groups of patients with atherosclerotic disease have generally shown that increased levels of fibrin fibrinogen degradation products (FFDP) in plasma are associated with an increased risk of severe atherosclerosis and an increased risk of vascular complications. Usually, elevated levels of FFDP, such as D-dimers, are considered as a marker of increased clotting activity. This assumption is one of the key elements of the controversy regarding cause and consequence of hypercoagulability. However, more and more finding indicated the close relations between FFDP and inflammatory reactions during atherogenesis. Firstly, FFDP levels are oftentimes associated with markers of inflammation. For an example, D-dimer level is often associated with C-reactive protein (CRP) and Il(interleukin)-6. In addition, FFDP often correlate with fibrinogen levels, which may be related to inflammation, but fibrinogen is also the substrate for fibrin, thus a more straightforward substrate-enzymecleavage product relation may also play a significant role.In this study, we aimed to investigate the roles of FFDP in macrophage-derived foam cell formation during atherogenesis. The following results were gained in this study:1. The macrophage-derived foam cells were cultured from human monocyte line U937 cells in addition with oxLDL. After U937 cells incubated with ox-LDL and treated with 0.3% Oil red O, many red pellets werefound in the plasma of the U937 cells. FFDP could significantly enhance the scavenger receptors SRI/SRII expression levels, which greatly increased the oxLDL uptake of macrophages.2. We cultured the primary rabbit aorta endothelial cells (RAEC) in vitro. Then the number of U937 cells adhering to RAEC monolayer was counted. FFDP could significantly enhance the adhesion of U937 cells to RAEC induced by ox-LDL>which indicated the advancing effects on the adhesion ructions of macrophages to endothelium.3. We use an Oligo Atherosclerosis Microarray in Super Array Company in USA to determine the effects of fibrin D-dimer fragments on the macrophage cell functions in atherosclerosis through determination on 128 genes related to atherosclerotic pathophysiological processes. The Microarray results proved 27 genes were enhanced by D-dimer fragments in over 2-fold of control. These 27 genes belong to 6 groups including adhesion molecules, extracellular molecules, lipid transport and metabolism related molecules, cell growth and proliferation molecules, transcription regulators and genes response to Stress.4. we forwarded to determine 5 gene expression levels by using SYBR real-time PCR, including VCAM1> MMP-9, OLR1, VEGFa and PPARa, which confirmed the up-regulation similar with Microarray results after treated with D-dimer.Therefore, our results provided the direct evidence on the pro-atherosclerotic roles of FFDP, as well as D-dimer, in macrophage functions, which mainly enhanced the inflammatory responses during macrophage-derived foam cell formation.