Year: 2011
Type: dissertation
Abstract: Thesis (Ph.D.)--Georgetown University, 2011.; Includes bibliographical references.; Text (Electronic thesis) in PDF format. Background: Most neurodegenerative diseases, such as Alzheimer's disease (AD), have been identified as multifactorial diseases characterized by a progressive decline in physiological functions. Impairment of the mitochondrial respiratory chain has been extensively described in relation to AD. It has been reported that the amyloid species Ab1-42 may be implicated in mitochondrial dysfunction, leading to cell death. Methods: Using the SK-N-AS human neuroblastoma cell line, confocal microscopy and immuno-electron microscopy the mitochondrial targeting of exogenous Ab1-42 was investigated. The type of Ab1-42 present in the mitochondrial fraction of Ab1-42-treated neuronal cells was examined by immunoblot analysis. The direct toxic effect of Ab1-42 on SK-N-AS cells and isolated rat brain mitochondria was investigated. Using human cell lines of various tissue origin and diverse self-aggregating peptides the specificity of the toxic effect Ab1-42 was evaluated. To further demonstrate the specificity of the phenomena observed, the steroidal caprospinol, a compound shown to bind to Ab1-42 and protect neuronal cells against Ab1-42 -induced neurotoxicity was used. Results: When applied on neuronal cells, Ab1-42 is taken up by the cells and is targeted to mitochondria in a time-dependent manner. Ab1-42 has deleterious effects on SK-N-AS cells and on isolated rat brain mitochondria in part by directly altering the mitochondrial function. On isolated rat brain mitochondria, Ab1-42 uncoupled the mitochondrial respiratory chain activity and inhibited specifically the complex IV without affecting the function of the other complexes. On SK-N-AS cells, Ab1-42 did not trigger DNA fragmentation or the release of caspase-dependent pro-apoptosis makers, thus ruling out an induction of apoptosis by Ab1-42. However Ab1-42 did increase the release of adenylate kinase, a mitochondrial enzyme that is released after the induction of the mitochondrial permeability transition pore. Caprospinol prevented and inhibited the Ab1-42 peptide internalization and targeting to neuronal cell mitochondria. Interestingly, caprospinol also protected the complex IV function and prevented the mitotoxic effect of carbonyl cyanide m-chlorophenylhydrazone, a pharmacological agent that mimics Ab1-42 in its action to uncouple the mitochondrial respiratory chain. Conclusion: Taken together these results suggest that exogenous Ab1-42 is targeted to the mitochondria where it exerts a direct and specific mitotoxicity. This mitotoxicity can be prevented by the neurosteroid derivative caprospinol.
Author: Laurent Tillement
Language: English
Subfield: Cellular and Molecular Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2240505197