The blood vessels of aging animals are characterized by a number of histological changes, including an increase in the number of vascular smooth muscle cells (VSMCs) and monocytes in the intima. These changes are likely to contribute to the increased occurrence and severity of vascular disease that is associated with aging. Advanced glycation endproducts of proteins (AGE) accumulate in the plasma and in tissues with age and at an accelerated rate in diabetes. In isolated vascular cells, AGEs induce a proxidant stress, leading to activation of pro-inflammatory events such as increased NF-kB, monocyte chemoattractant protein-1, and PDGF B chain activity, all of which are likely to contribute to vascular lesion development. Our research efforts are focussed on identifying the signaling pathways by which AGEs affect gene expression so that molecular strategies can be developed to block their effects. Our results indicate that signaling is initiated by the binding of AGEs to a unique receptor called RAGE. We have cloned RAGE from rat intimal vascular smooth muscle cells and constructed epitope-tagged wild type and mutant receptors and shown that transfection of wild type receptor leads to increased NF-kB activity in response to AGEs. Mutant receptor in which the cytosolic tail has been removed, however, do not result in increased NF-kB activity, but in fact block the ability of co-transfected wild type receptors to signal. These observations provide the first demonstration that RAGE may act directly to engage intracellular signaling events and suggest that truncated RAGE may act as a dominant negative receptor to block the signaling effects of AGEs. These observations will be exploited to determine the role of AGEs in in vivo models of vascular injury using transgenic and knockout technologies. In addition, interaction cloning techniques will be used to identify intracellular proteins associated with the receptor.
