Alzheimer's Disease: Developing a Mechanistic View via Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that has a complex and highly debated etiology. AD pathogenesis theories vary widely between individuals and disciplines. Some prefer the amyloid cascade hypothesis, which asserts that the generation of amyloid-beta (Aβ) -rich senile plaques (SPs) by β-secretase generated mutations of the amyloid precursor protein (APP) are the primary cause of neuronal death and dysfunction leading to dementia. Others gravitate toward the more broad oxidative stress and inflammation hypotheses. To combat this diverseness, analytical and biochemical methods are employed to enhance understanding of the latent mechanisms involved in the disease onset and progression. Mass spectrometry-based molecular composition analysis is of particular significance for use in neurodegenerative disease research. The research presented in this dissertation utilizes novel MALDI-TOF MS developments and sample preparation methods for identifying biological compounds indicative of AD from human post-mortem intact tissue sections, and isolated SPs, and their application in imaging mass spectrometry (IMS). A novel laser-induced in-source decay (ISD) fragmentation method by MALDI-TOF MS is described for the identification of Aβ in complex biological systems. Additionally, bottom-up and top-down proteomics are utilized to develop a thorough survey of the components co-isolated within SPs, including but not limited to Aβ-related peptides, as part of the plaque isolation procedure. Relative magnitude of protein expression is determined by applied MALDI methods. All mass spectrometry methods and sample preparation techniques introduced herein allow for the simplified, yet thorough, analysis of AD- affiliated proteins and peptides. The identities of the proteins found to exist within SPs using the described methods, pave the way for novel AD research in relation to potential molecular targets for future disease therapies.