Aβ [25–35] Peptide and Iron Promote Apoptosis in Lymphocytes by an Oxidative Stress Mechanism: Involvement of H 2O 2, Caspase-3, NF-κB, p53 and c-Jun

Abstract

The Aβ deposition in the neuritic plaques is one of the major neuropathological hallmarks of the Alzheimer disease (AD). Studies in vitro have demonstrated that the Aβ 25–35 fragment, which contains the cytotoxic functional sequence of the amyloid peptide, induces neurotoxicity and cell death by apoptosis. Despite intense investigations, a complete picture of the precise molecular cascade leading to cell death in a single cellular model is still lacking. In this study, we provide evidence that Aβ 25–35 induce apoptosis either alone or in presence of iron in peripheral blood lymphocytes cells (PBL) in a concentration-dependent fashion by an oxidative stress mechanism involving: (1) the production of hydrogen peroxide (H 2O 2), reflected by rhodamine-positive fluorescent cells, (2) activation and/or translocation of NF-κB, p53 and c-Jun transcription factors showed by immunocytochemical diaminobenzidine positive nuclei, (3) activation of NF-κB complex by electrophoretic mobility shift assay/immuno-blotting/and ammonium pyrrolidinedithiocarbamate (PDTC) inhibition, (4) caspase-3 activation, reflected by caspase Ac-DEVD-cho inhibition, (5) mRNA synthesis de novo according to actinomycin D cell death inhibition. These results are consistent with the notion that the Aβ 25–35/H 2O 2 generation precede the apoptotic process and that once H 2O 2 is generated, it is able to trigger a specific cell death signalisation. Thus, taken together these results, we present a well-ordered cascade of the major molecular events leading PBL to apoptosis. These results may contribute to explain the importance of Aβ alone or in the presence of redox-available iron in association with Aβ plaques (and neurofibrillary tangles) in AD brains and the significant role played by H 2O 2 as a second messenger of death signal in some degenerative diseases linked to oxidative stress stimuli.