Multiple signaling events in amyloid β-induced, oxidative stress-dependent neuronal apoptosis

Current evidence suggests that amyloid β peptides (Aβ) may play a major role in the pathogenesis of Alzheimer’s disease by eliciting oxidative stress and neuronal apoptosis. In this study we have used differentiated SK-N-BE neurons to investigate molecular mechanisms and regulatory pathways underlying apoptotic neuronal cell death elicited by Aβ1–40 and Aβ1–42 peptides as well as the relationships between apoptosis and oxidative stress. Aβ peptides, used at concentrations able to induce oxidative stress, elicit a classic type of neuronal apoptosis involving mitochondrial regulatory proteins and pathways (i.e. affecting Bax and Bcl-2 protein levels as well as release of cytochrome c in the cytosol), poly-ADP rybose polymerase cleavage and activation of caspase 3. This pattern of neuronal apoptosis, that is significantly prevented by α-tocopherol and N-acetylcysteine and completely abolished by specific inhibitors of stress-activated protein kinases (SAPK) such as JNKs and p38MAPK, involved early elevation of p53 protein levels. Pretreatment of neurons with α-pifithrin, a specific p53 inhibitor, resulted in a 50-60% prevention of Aβ induced apoptosis. These results suggest that oxidative stress - mediated neuronal apoptosis induced by amyloid β operates by eliciting a SAPK–dependent multiple regulation of pro-apoptotic mitochondrial pathways involving both p53 and bcl-2.