[Show abstract][Hide abstract] ABSTRACT: Increased circulating endothelial microparticles, resulting from vascular endothelium dysfunction, and plasmacytoid dendritic cell activation are both encountered in common inflammatory disorders. The aim of our study was to determine whether interactions between endothelial microparticles and plasmacytoid dendritic cells could contribute to such pathologies.
Microparticles generated from endothelial cell lines, platelets or activated T cells were incubated with human plasmacytoid dendritic cells sorted from healthy donor blood or with monocyte-derived dendritic cells. Dendritic cell maturation was evaluated by flow cytometry, cytokine secretion as well as naive T-cell activation and polarization. Labeled microparticles were also used to study cellular interactions.
Endothelial microparticles induced plasmacytoid dendritic cell maturation. In contrast, conventional dendritic cells were resistant to endothelial microparticle-induced maturation. In addition to upregulation of co-stimulatory molecules, endothelial microparticle-matured plasmacytoid dendritic cells secreted inflammatory cytokines (interleukins 6 and 8, but no interferon-alpha) and also induced allogeneic naive CD4(+) T cells to proliferate and to produce type 1 cytokines such as interferon-gamma and tumor necrosis factor-alpha. Endothelial microparticle endocytosis by plasmacytoid dendritic cells appeared to be required for plasmacytoid dendritic cell maturation. Importantly, the ability of endothelial microparticles to induce plasmacytoid dendritic cells to mature was specific as microparticles derived from activated T cells or platelets (the major source of circulating microparticules in healthy subjects) did not induce such plasmacytoid dendritic cell maturation.
Our data show that endothelial microparticles specifically induce plasmacytoid dendritic cell maturation and production of inflammatory cytokines. This novel activation pathway may be implicated in various inflammatory disorders and endothelial microparticles could be an important immunmodulatory therapeutic target.
[Show abstract][Hide abstract] ABSTRACT: Different genetic alterations may lead to type I interferon (IFN) overproduction in human systemic lupus erythematosus (SLE). The increased bioavailability of type I IFN contributes to peripheral tolerance breakdown through the activation of immature myeloid dendritic cells (mDCs). IFN-matured mDCs activate autoreactive T cells. These cells, together with plasmacytoid DCs, help expand autoreactive B cells. IFN-matured DCs also activate cytotoxic CD8+ T cells, possibly increasing apoptotic cell availability. The capture of apoptotic cells by mDCs and of nucleic acid-containing immune complexes by plasmacytoid DCs and B cells amplifies the autoimmune reaction leading to disease manifestations. Genetic alterations in lineages other than B cells might explain other autoimmune syndromes where type I IFNs appear to be involved.
[Show abstract][Hide abstract] ABSTRACT: Microparticles are submicron vesicles shed from plasma membranes in response to cell activation, injury, and/or apoptosis. The measurement of the phospholipid content (mainly phosphatidylserine; PSer) of microparticles and the detection of proteins specific for the cells from which they are derived has allowed their quantification and characterization. Microparticles of various cellular origin (platelets, leukocytes, endothelial cells) are found in the plasma of healthy subjects, and their amount increases under pathological conditions. Endothelial microparticles (EMP) not only constitute an emerging marker of endothelial dysfunction, but are also considered to play a major biological role in inflammation, vascular injury, angiogenesis, and thrombosis. Although the mechanisms leading to their in vivo formation remain obscure, the release of EMP from cultured cells can be caused in vitro by a number of cytokines and apoptotic stimuli. Recent studies indicate that EMP are able to decrease nitric-oxide-dependent vasodilation, increase arterial stiffness, promote inflammation, and initiate thrombosis at their PSer-rich membrane, which highly co-expresses tissue factor. EMP are known to be elevated in acute coronary syndromes, in severe hypertension with end organ damage, and in thrombotic thrombocytopenic purpura, all conditions associated with endothelial injury and pro-thrombotic state. The release of EMP has also been associated with endothelial dysfunction of patients with multiple sclerosis and lupus anticoagulant. More recent studies have focused on the role of low shear stress leading to endothelial cell apoptosis and subsequent EMP release in end-stage renal disease. Improved knowledge of EMP composition, their biological effects, and the mechanisms leading to their clearance will probably open new therapeutic approaches in the treatment of atherothrombosis.
Cell and Tissue Research 12/2008; 335(1):143-51. DOI:10.1007/s00441-008-0710-9 · 3.57 Impact Factor
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