Peroxisome proliferator-activated receptor gamma is expressed in hippocampal neurons and its activation prevents beta-amyloid neurodegeneration: role of Wnt signaling

Abstract

The molecular pathogenesis of Alzheimer's disease (AD) involves the participation of the amyloid-beta-peptide (Abeta), which plays a critical role in the neurodegeneration that triggers the disease. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors, which are members of the nuclear receptor family. We report here that (1) PPARgamma is present in rat hippocampal neurons in culture. (2) Activation of PPAR-gamma by troglitazone and rosiglitazone protects rat hippocampal neurons against Abeta-induced neurodegeneration, as shown by the 3-[4,5 -2yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay, immunofluorescence using an anti-heavy neurofilament antibody, and quantitative electron microscopy. (3) Hippocampal neurons treated with several PPAR-gamma agonists, including troglitazone, rosiglitazone, and ciglitazone, prevent the excitotoxic Abeta-induced rise in bulk-free Ca2+. (4) PPARgamma activation results in the modulation of Wnt signaling components, including the inhibition of glycogen synthase kinase-3beta (GSK-3beta) and an increase of the cytoplasmic and nuclear beta-catenin levels. We conclude that the activation of PPARgamma prevents Abeta-induced neurodegeneration by a mechanism that may involve a cross talk between neuronal PPAR-y and the Writ signaling pathway. More important, the fact that the activation of PPAR-y attenuated Abeta-dependent neurodegeneration opens the possibility to fight AD from a new therapeutic perspective. (C) 2004 Published by Elsevier Inc.