Amyloid β42 (Aβ42) plays a decisive role in the pathology of Alzheimer's disease. The Aβ42 peptide can aggregate into various supramolecular structures, with oligomers being the most toxic form. However, different Aβ species that cause different effects have been described. Many cell death pathways can be activated in connection with Aβ action, including apoptosis, necroptosis, pyroptosis, oxidative stress, ferroptosis, alterations in mitophagy, autophagy, and endo/lysosomal functions. In this study, we used a model of differentiated SH-SY5Y cells and applied two different Aβ42 preparations for 2 and 4 days. Although we found no difference in the shape and size of Aβ species prepared by two different methods (NaOH or NH4OH for Aβ solubilization), we observed strong differences in their effects. Treatment of cells with NaOH-Aβ42 mainly resulted in damage of mitochondrial function and increased production of reactive oxygen species, whereas application of NH4OH-Aβ42 induced necroptosis and first steps of apoptosis, but also caused an increase in protective Hsp27. Moreover, the two Aβ42 preparations differed in the mechanism of interaction with the cells, with the effect of NaOH-Aβ42 being dependent on monosialotetrahexosylganglioside (GM1) content, whereas the effect of NH4OH-Aβ42 was independent of GM1. This suggests that, although both preparations were similar in size, minor differences in secondary/tertiary structure are likely to strongly influence the resulting processes. Our work reveals, at least in part, one of the possible causes of the inconsistency in the data observed in different studies on Aβ-toxicity pathways.

• Keywords
• Alzheimer´s disease, Amyloid β42, Apoptosis, Cell death, GM1, Necroptosis, Reactive oxygen species,
• MeSH
• Alzheimer Disease metabolism   pathology   MeSH
• Amyloid beta-Peptides * metabolism   pharmacology   MeSH
• Apoptosis * drug effects   MeSH
• Cell Death drug effects   MeSH
• Humans MeSH
• Mitochondria metabolism   drug effects   MeSH
• Cell Line, Tumor MeSH
• Necroptosis drug effects   MeSH
• Neuroblastoma * pathology   metabolism   MeSH
• Oxidative Stress drug effects   MeSH
• Peptide Fragments * pharmacology   MeSH
• Reactive Oxygen Species * metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• amyloid beta-protein (1-42) MeSH Browser
• Amyloid beta-Peptides * MeSH
• Peptide Fragments * MeSH
• Reactive Oxygen Species * MeSH

The physical stability of peptide-based drugs is of great interest to the pharmaceutical industry. Glucagon-like peptide 1 (GLP-1) is a 31-amino acid peptide hormone, the analogs of which are frequently used in the treatment of type 2 diabetes. We investigated the physical stability of GLP-1 and its C-terminal amide derivative, GLP-1-Am, both of which aggregate into amyloid fibrils. While off-pathway oligomers have been proposed to explain the unusual aggregation kinetics observed previously for GLP-1 under specific conditions, these oligomers have not been studied in any detail. Such states are important as they may represent potential sources of cytotoxicity and immunogenicity. Here, we identified and isolated stable, low-molecular-weight oligomers of GLP-1 and GLP-1-Am, using size-exclusion chromatography. Under the conditions studied, isolated oligomers were shown to be resistant to fibrillation or dissociation. These oligomers contain between two and five polypeptide chains and they have a highly disordered structure as indicated by a variety of spectroscopic techniques. They are highly stable with respect to time, temperature, or agitation despite their noncovalent character, which was established using liquid chromatography-mass spectrometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results provide evidence of stable, low-molecular-weight oligomers that are formed by an off-pathway mechanism which competes with amyloid fibril formation.

• Keywords
• aggregation, amyloid, glucagon-like peptide 1, oligomers, self-assembly,
• MeSH
• Amyloid chemistry   MeSH
• Amyloid beta-Peptides chemistry   MeSH
• Diabetes Mellitus, Type 2 * MeSH
• Chromatography, Gel MeSH
• Glucagon-Like Peptide 1 * MeSH
• Humans MeSH
• Peptide Fragments chemistry   MeSH
• Peptides MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Amyloid MeSH
• Amyloid beta-Peptides MeSH
• Glucagon-Like Peptide 1 * MeSH
• Peptide Fragments MeSH
• Peptides MeSH