P4-299: Neuron-binding autoantibodies in human sera enhance Abeta42 accumulation in adult mouse brain neurons

Abstract

of Alzheimer’s disease (AD), and it is characterized by the deposition of beta-amyloid (A ) in cerebral cortical and meningeal blood vessels (Kawai M. et al., 1993), inducing degeneration of vascular cells. Semicarbazide-sensitive amine oxidase (SSAO) [E.C. 1.4.3.6] is present in vascular cells and in plasma. It metabolizes primary amines (Lyles GA., 1996) generating hydrogen peroxide (H2O2), ammonia (NH3) and the corresponding aldehyde, that contribute to the oxidative stress, advanced glycation end-product generation (GubisneHaberle D. et al., 2004), and beta amyloid aggregation (Chen K. et al., 2006). Furthermore in endothelial cells, SSAO is induced under inflammatory conditions (Smith D.J. et. al., 1998). We have reported that SSAO is overexpressed in cerebrovascular tissue of patients with CAA-AD, and that it colocalizes with beta-amyloid deposits (Ferrer I. et al., 2002). This over-expression correlates with high SSAO activity in plasma of severe AD patients (del Mar Hernandez M. et al., 2005). We have also described that plasma SSAO is able to induce apoptosis in vascular cells (Hernandez M. et.al., 2006). The aim of this work is to demonstrate whether A is able to induce SSAO overexpression in HUVEC cells as vascular cell type. Methods: Because of the SSAO/ VAP-1 expression fenotype is lost in cultured cells, HUVEC (human umbilical vein endothelial cells) cells, were stably transfected with vector pcDNA 3.1 containing hVAP-1/SSAO. Cells were treated with A 1-40 Dutch type (mutation E22Q) and/or Methylamine as SSAO substrate. Cell viability, SSAO activity and its expression were determined using specific antibodies against SSAO. Results: Herein we report that A 1-40 E22Q induces the SSAO activity and expression in HUVEC cells. This increasing activity promotes oxidative stress that enhances the toxicity generated by A alone. This toxicity is reverted by specific SSAO inhibitors, confirming SSAO as the responsible of such effect. Conclusions: These results allow us to postulate that deposits of A in cerebrovascular tissue, induce SSAO expression that may contribute to the vascular damage associated to CAA-AD.