Amidation of beta-amyloid peptide strongly reduced the amyloidogenic activity without alteration of the neurotoxicity.
Beta-amyloid accumulates in cerebral deposits in Alzheimer's disease, so to test the correlation between the neurotoxic and fibrillogenic capacity of beta-amyloid, we synthesized a peptide homologous to fragment 25-35 of beta-amyloid (beta25-35) and amidated at the C-terminus (beta25-35-NH2). As the amidation strongly reduced the amyloidogenic capacity of beta25-35, we compared its neurotoxic activity in the amidated (beta25-35-NH2) and nonamidated forms. The viability of primary cultures from fetal rat hippocampus was reduced in a dose-related manner (10-100 microM) similarly by beta25-35 and beta25-35-NH2, whereas a scrambled peptide, amidated or nonamidated, did not alter the neuronal viability. The neurotoxic activity of beta25-35-NH2 is mediated by apoptosis as demonstrated by morphological and biochemical investigations. Electron microscopy examination of culture media with beta25-35 or beta25-35-NH2 incubated with neuronal cells for 7 days confirmed the high level of fibrillogenic activity of beta25-35 and the almost total absence of fibrils in the solution with beta25-35-NH2. Furthermore, staining with thioflavine S was used to identify amyloid fibrils, and only the cultures exposed to beta25-35 exhibited intense staining associated with neuronal membranes. These data indicate that the neurotoxic activity of the beta-amyloid fragment is independent of the aggregated state of the peptide.
Forloni
G
G
Biology of Neurodegenerative Disorders, Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy.
Lucca
E
E
Angeretti
N
N
Della Torre
P
P
Salmona
M
M
D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media; D053938:DNA Fragmentation; D005333:Fetus; D006624:Hippocampus / Q000166:cytology / Q000473:pathology*; D008854:Microscopy, Electron; D009454:Neurofibrils / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D009498:Neurotoxins; D010446:Peptide Fragments / Q000737:chemistry / Q000633:toxicity*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000633:toxicity; D051381:Rats
D016229:Amyloid beta-Peptides; D003470:Culture Media; D009498:Neurotoxins; D010446:Peptide Fragments; D010455:Peptides; C074636:amyloid beta-protein (25-35)