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Apoptosis-mediated neurotoxicity induced by beta-amyloid and PrP fragments
G Forloni1, O Bugiani, F Tagliavini
1Istituto di Ricerche, Farmacologiche Mario Negri, Milano, Italy.
Abstract:
The neurotoxic activity of beta-amyloid (beta A) and prion protein (PrP) fragments contributed to the hypothesis concerning a causal role of amyloid deposits in Alzheimer disease (AD) and in prion-related encephalopathies. In this study, we investigated some aspects of the molecular mechanisms associated with neurotoxic activity of synthetic peptides homologous to beta A (beta 25-35) or PrP (PrP106-126) fragments. Chronic (5-7 d) exposure to both peptides induced neuronal death by apoptosis, as suggested by biochemical and morphological analysis. The apoptotic mechanism was confirmed by ultrastructural examination. The intracellular cascade of events activated by peptides was investigated by Northern blot and PCR analysis of expression of early genes (c-fos, c-jun, c-myc) and other proteins (p53, SGP-2 bcl-2, HSP70, Ich-1) potentially involved in apoptosis. With the exception of bcl-2 mRNA decrease and a slight increase of SGP-2 in PrP106-126-treated cells, no consistent alterations of these mRNA expressions were found in neuronal cells exposed to beta 25-35 or PrP106-126. Furthermore, we synthesized amidated homologs of both peptides with low amyloidogenic activity to test directly the relationship between amyloid fibrils and cell death. The neurotoxicity exhibited by PrP106-126-NH2 was similar to that observed with original peptide, whereas the amidation of beta 25-35 partially reduced the neurotoxicity of this peptide.
Insights
Beta-amyloid (beta A) and prion protein (PrP) fragments induce neuronal apoptosis. This study explores their neurotoxic mechanisms, finding limited changes in early gene expression but confirming cell death pathways in Alzheimer disease and prion-related encephalopathies.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Amyloid deposits are implicated in Alzheimer disease (AD) and prion-related encephalopathies.
- Beta-amyloid (beta A) and prion protein (PrP) fragments exhibit neurotoxic activity.
Purpose of the Study:
- Investigate molecular mechanisms of neurotoxicity of beta A (beta 25-35) and PrP (PrP106-126) peptides.
- Determine the role of amyloid fibrils in peptide-induced neuronal cell death.
Main Methods:
- Chronic exposure of neuronal cells to synthetic beta 25-35 and PrP106-126 peptides.
- Biochemical, morphological, and ultrastructural analysis to detect apoptosis.
- Northern blot and PCR to assess gene and protein expression (c-fos, c-jun, c-myc, p53, bcl-2, SGP-2, HSP70, Ich-1).
- Synthesis and testing of amidated peptide analogs with reduced amyloidogenic potential.
Main Results:
- Both beta 25-35 and PrP106-126 peptides induced neuronal apoptosis.
- Apoptotic mechanism confirmed by biochemical, morphological, and ultrastructural data.
- Limited alterations in early gene and apoptosis-related protein mRNA expression observed, except for bcl-2 and SGP-2 with PrP106-126.
- Amidated PrP106-126-NH2 retained neurotoxicity; amidation of beta 25-35 partially reduced its neurotoxicity.
Conclusions:
- Synthetic beta A and PrP fragments trigger neuronal apoptosis through specific molecular pathways.
- The relationship between amyloid fibril formation and neurotoxicity is complex and peptide-dependent.
- Findings contribute to understanding neurodegenerative mechanisms in AD and prion diseases.