RAGE is a multiligand receptor in the immunoglobulin superfamily of cell surface molecules which is a signal transduction receptor for S100/calgranulins, closely associated with inflammatory processes. Interaction of S100/calgranulins with RAGE-bearing cells caused a proinflammatory phenotype: mononuclear phagocytes (MPs) elaborate Interleukin (IL)-1beta and tumor necrosis factor-alpha, lymphocytes produce IL-2, and endothelial cells express cell adherence molecules. In vivo, blockade of RAGE or neutralization of S100/calgranulins prevented delayed-type hypersensitivity provoked by methylated albumin, prevented colitis in IL-10 null mice, and inhibited collagen-induced arthritis autoimmune diabetes. These data suggested a potentially fundamental role for RAGE in cell-mediated immune/inflammatory processes, and led us to perform pilot studies in Experimental Autoimmune Encephalitis (EAE). Using a model in which EAE was induced by immunization of Bl0.PL mice with myelin basic protein-derived peptide (MBP), lymph node cells and central nervous system (CNS) inflammatory infiltrates demonstrated an increase in RAGE-bearing MPs and CD4+ T cells. Administration of a soluble form of RAGE spanning the extracellular domain (sRAGE) prevented/markedly delayed the onset of clinical symptoms and inflammatory infiltrates in the CNS, though sRAGE-treated mice displayed no suppression of MBP-reactive CD4+ T cells. These data lead the proposal that RAGE, expressed by encephalitogenic CD4+ T cells and macrophages, potentially impacts key cellular events underlying EAE.
Our first aim i s to firmly establish whether RAGE and Sl00/calgranulin ligands have a central role in the pathogenesis of EAE, induced by immunization or infusion of an encephalitogenic CD4+ Th1 T cell clone, by performing experiments in RAGE null mice, transgenic (Tg) mice expressing a rearranged T cell receptor specific for MBP, and using anti-RAGE and/or anti-EN-RAGE F (ab') 2 in wild-type mice.
Our second aim i s to analyze mechanisms through which RAGE contributes to the pathogenesis of EAE by determining the role of RAGE on CD4+ lymphocytes and MPs. Transgenic mice with targeted expression of a dominant negative form of RAGE in CD4+ lymphocytes or MPs will be used to assess the contribution of RAGE to: activation of encephalitogenic CD4+ T-cells by MBP, their differentiation into Th1/Th2 cells, their migration into the CNS and subsequent induction of inflammatory events.
