Restoring the balance in the kinetic network of Aβ aggregation as a drug discovery strategy for Alzheimer’s Disease

Alzheimer’s disease (AD) is the most prevalent cause of dementia that affects over 50 million people, and is associated strongly with the aggregation of the amyloid-β peptide (Aβ). Even though a variety of strategies has been developed towards inhibiting the aggregation of Aβ, no disease-modifying treatment has so far reached the clinic. This failure is in part due to i) an incomplete knowledge of the aggregation process of Aβ, especially in the context of the complex biological environment, and ii) an unclear mechanism of action of potential inhibitors of this process. In this thesis, we address the above points using a combination of a chemical kinetics based experimental assay and a theoretical analysis that dissects the macroscopic reaction observed from experimental measurements into individual rates of microscopic reaction steps. By coupling these analyses to a range of other biophysical techniques, we can quantitatively determine the modulation of the complex reaction network of Aβ using a bottom-up approach. In this thesis, we begin with an introduction of AD, with a specific emphasis on its association with the aggregation of the Aβ peptide (Chapter 1). We also discuss the potentials and limitations of current therapeutic approaches in AD. Subsequently, we describe in detail the experimental and theoretical methods of the chemical kinetics based approach used in understanding the aggregation of Aβ and quantitatively determining the effect of modulators on the kinetic network (Chapter 2). Using this approach, we demonstrate how the aggregation process of Aβ is modulated by relevant biological factors that have been associated with AD (Chapter 3). These include cholesterol-containing lipids which accelerate the aggregation, proteins with potential chaperonic functions which inhibit the aggregation, and metal ions which promote the formation of polymorphic aggregated structures. These results provide greater insights into the physiological regulation of the aggregation of Aβ, and how it leads to the onset of AD when the homeostatic control is progressively compromised, especially as we age. By harnessing the above knowledge of how homeostatic imbalance fails to regulate the aggregation of Aβ, we describe the potential use of small molecules to inhibit aggregation and potentially restore the balance (Chapter 4). We use chemical kinetics to develop a drug discovery approach, known as SAR by kinetics (SKAR), that is used to systematically find and optimise the potency of small molecules in reducing the rate of formation of oligomers, which are highly cytotoxic intermediates that form transiently during the aggregation of Aβ. SKAR allows us to determine the relationship between the chemical structure of a molecule and its kinetic inhibitory potency, and thus iteratively improve molecules as potential drug candidates, which was impossible to achieve with conventional methods. Finally, we summarise the work in this thesis (Chapter 5), and discuss the potential opportunities and challenges, as we aim towards a more complete understanding of how the kinetic network of Aβ is regulated in the brain, dysregulated in disease, and how we can restore the balance as a means of drug discovery against AD.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2020

Author dc:creator

• Chia, Sean Keng Rui

Advisor dc:contributor.advisor

• Vendruscolo, Michele

• Chemical Kinetics
• Amyloid-β
• Drug Discovery

Licence

• https://www.repository.cam.ac.uk/bitstreams/e7d76def-d67d-4c7b-83cf-2607c42acedb/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

en

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.48813

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/301742