Abeta oligomers and fibrillar aggregates induce different apoptotic pathways in LAN5 neuroblastoma cell cultures.
Fibril deposit formation of amyloid beta-protein (Abeta) in the brain is a hallmark of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Abeta oligomers, which have been found in soluble brain extracts of AD patients, rather than to insoluble fibers. Here we report a study of the toxicity of two distinct forms of recombinant Abeta small oligomers and fibrillar aggregates to simulate the action of diffusible Abeta oligomers and amyloid plaques on neuronal cells. Different techniques, including dynamic light scattering, fluorescence, and scanning electron microscopy, have been used to characterize the two forms of Abeta. Under similar conditions and comparable incubation times in neuroblastoma LAN5 cell cultures, oligomeric species obtained from Abeta peptide are more toxic than fibrillar aggregates. Both oligomers and aggregates are able to induce neurodegeneration by apoptosis activation, as demonstrated by TUNEL assay and Hoechst staining assays. Moreover, we show that aggregates induce apoptosis by caspase 8 activation (extrinsic pathway), whereas oligomers induce apoptosis principally by caspase 9 activation (intrinsic pathway). These results are confirmed by cytochrome c release, almost exclusively detected in the cytosolic fraction of LAN5 cells treated with oligomers. These findings indicate an active and direct interaction between oligomers and the cellular membrane, and are consistent with internalization of the oligomeric species into the cytosol.
Picone
Pasquale
P
Dipartimento di Chimica e Tecnologie Farmaceutiche, University of Palermo, Palermo, Italy.
Carrotta
Rita
R
Montana
Giovanna
G
Nobile
Maria Rita
MR
San Biagio
Pier Luigi
PL
Di Carlo
Marta
M
D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D009447:Neuroblastoma / Q000473:pathology*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity*; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013379:Substrate Specificity; D013997:Time Factors
D016229:Amyloid beta-Peptides; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); D045304:Cytochromes c