Role Of Dendritic Cells-Mediated Immunologic Mechanism In The Process Of Atherosclerosis

Atherosclerosis and its clinic consequence, such as conorary atherosclerotic disease, have become the leading health problem worldwide. Accumulating evidence suggests that atherosclerosis is an autoimmune disease. It is thought that the immune response, predominantly Th1 response, induced by endogenous antigens, such as ox-LDL, HSP 60, and exogenous antigens,such as microbes, is the cause of AS. Dendritic cells (DCs) are the the most important and professional antigen presenting cells (APCs) in the body, and play a key role in regulating immune process. It had been found that DCs exist in the human vascular wall, participating in the whole pathologic course of the initiation and development of AS. However, the effect of DCs and the related mechanism in atherosclerosis are not clearly elucidated. The aim of this study is to explore the role of DCs in the Immunologic Mechanism of atherosclerosis in the aspect of pathology, cellular level and clinic epidemiology. It is made up of three parts:Part I: The Distribution of Dendritic Cells and Dendritic Cells-Derived-Foam Cells in Atherosclerotic Plaque of Rabbit ModelObjective: To investigate the distribution of dendritic cells (DCs) and DCs-derived-foam cells in atherosclerotic plaque of rabbit model.Methods: Aortas were acquired from high-cholesterol diet induced atherosclerotic rabbit model and underwent immunohistochemical and electronmicroscopic examination. A monoclonal anti-S-100 antibody was used to identity foam cells derived from dendritic cells, and electron microscopy were used to observe the ultrastructure of these cells.Results: Few cells expressing S-100 were observed in the intima of normal artery. Cells expressing S-100 were present around foam cell-rich areas within intimal atherosclerotic lesions in atherosclerotic artery and some displayed typical appearance of foam cells. Electron microscopy demonstrated that some of dendritic cells have a large number of lipid droplets filled in their cytoplasm, and exhibit thetypical characteristics of foam cells.Conclusion: Our results demonstrated that dendritic cells is ecpressed in the AS plaque of rabbit model, and can derive into foam cells in the proatherosclerosis conditions, which imply that dendritic cell is a new source of foam cells in atherosclerotic plaque, which may be of great importance in atherosclerosis.Part II: Immune Maturation of Human Monocyte Derived Dendritic Cells Induced by Oxidized-Low Density Lipoprotein and Inhibited by FenofibrateObjective: To investigate the effect of oxidized low-density lipoprotein (ox-LDL) and peroxisome proliferator-activated receptors α (PPAR α ) agonist fenofibrateon the immune maturation of monocyte -derived dendritic cells (DC). Methods: Monocytes were purified (over 98%) using Anti-CD 14 microbeads, After cultured with DC Cellgro medium containing recombinated human granulocyte-macrophage colony stimulating factor (rhGM-CSF) (100ng/ml) and recombinated human interleukin-4 (rhIL-4) (20ng/ml) for 5days, monocytes were derived into immature DCs. Human monocyte-derived DCs were incubated with fenofibrate (100 μ mol/L) for 24 hours,and were subsequently stimulated with ox-LDL (50 μg/mL)for another 48 hours. The immunophenotypic expressions (CD1a, CD40, CD86, and HLA-DR) were analyzed by FACS and endocytosis function by FITC-dextran, and the cytokines secretions of culture supernatants (IL-12,IL-10,TNF- α ) were measured with ELISA.Results: Fenofibrate reduced ox-LDL induced immunophenotypic expressions of DC (CD40, CDla,CD86 and HLA-DR). Ox-LDL inhibited the endocytosis of DC, which partly was prevented by fenofibrate; fenofibrate attenuated ox-LDL induced cytokine secretions of DC (IL-12, IL-10, TNF α ).Conclusion: PPAR a agonist fenofibrate partly inhibits ox-LDL induced immune maturation of DC, through which it may play an anti-atherosclerosis effect.Part III: Peripheral blood dendritic cells in coronary atheroscleroticdiseaseObjectives: Dendritic cells (DCs) subsets, Myeloid DC (mDC) and plasmacytoid DC (pDC), regulate immune reactions by polarising naive T-helper cells into a Th1 or Th2 response, respectively. In this study we examined total peripheral blood DCs, mDC and pDC subsets in coronary atherosclerotic disease.Methods:Thirty —two male patients underwent coronary angiography(CAG) examination were devided into group of coronary atherosclerotic disease (CAD, n=21) and group of CAG normal (n=11). The percentage and absolute number of peripheral blood DC and DC subsets were measured by three color. DC were defined as Lin1~-HLA-DR~+, and MDC as Lin1~-HLA-DR~+CD11c~+, PDC as Lin1~-HLA-DR~+CD123~+.Results: CAD patients had higher absolue number of peripheral blood DCs compared to group of CAD normal (p = 0.04), but not the pencent of peripheral blood DCs(p=0.07); Furtherover, the pencent and absolute number of the mDC fraction was significantly increased compared to group of CAG normal (p<0.05) , but not the pencent and absolute number of the pDC fraction (p> 0.05) . At the same time, the ratio of MDC/PDC was significantly elevated compared to group of CAG normal (p=0.01) .Conclusions: Total peripheral blood DCs are elevated in CAD patients due to an increase in the mDC subset, which maybe the cause of enhenced Th1 response in CAD.