Ebanks, Kirsten Rene Miriam; (2024) Converging Mechanisms of Lipid Metabolism and Lysosomal Damage in the Pathogenesis of Parkinson’s Disease. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Introduction: Parkinson’s disease (PD) is a common age-related neurodegenerative disorder with disabling motor symptoms and no available disease modifying treatment. While commonly believed to be a proteinopathy, specifically a synucleinopathy, recent studies have suggested a prominent role for lipids in pathogenesis. Studies have shown that many PD associated genes play a role in lysosomal function and cell type specific lipid storage changes have been shown in PD patient brains and lipid droplet binding may play a role in the oligomerization of α-synuclein, the protein present in the disease’s hallmark Lewy bodies. Methodology: This thesis used various techniques to better understand PD relevant disease pathways particularly as they apply to lysosomal function and lipid processing. In Chapter 2, a bioinformatic analysis of existing and publicly available genetic datasets for both PD and common co-morbid disorders such as type 2 diabetes was conducted to unearth common pathways of dysfunction using analysis techniques such as association rule mining. In chapter 3, the targets selected in chapter 2 where investigated in human PD and control tissue. Immunohistochemistry and western blot analysis were used to understand differences in protein expression in control, early and late stage PD cases across four brain regions. In Chapter 4, H4 astrogiloma, SH-SY5Y neuronblastoma and SH-SY5Y overexpressing alpha synuclein cell lines were used to better understand fatty acid storage and trafficking across cell lines as well as the role alpha synuclein might play in these processes. Treatments of oleic acid, palmitic acid, chloroquine and LLOMe were used. The cells were stained for lipid droplets, lysosomes, and mitochondria and morphological changes were analyzed to understand the effects of these treatments. Results: Bioinformatic analysis showed common pathways focusing on lipid based functions and cellular trafficking being selected for further investigation. Assessment of relevant markers in human PD and control tissue showed the most promising target was found to be fatty acid binding protein 7 (FABP7) with expression being increased in the frontal cortex of neocortical PD cases when compared to controls, as shown by western blot. This increase appeared to be largely astrocytic based on IHC. Further investigation into the role and lipids and fatty acids in cells showed changes to mitochondrial morphology, such as an increase in mitochondrial elongation in response to fatty acid treatments in H4 cells but not in SH-SY5Y cells, as well as lipid droplet and lysosomal organization across cell types. Conclusion: Emerging evidence suggests that lipids and lipid-related pathways may significantly contribute to its pathogenesis. This thesis aimed to explore these lipid-based mechanisms using a multi-faceted approach, encompassing bioinformatics, tissue analysis, and cell culture experiments. We have shown how fatty acids and fatty acid binding proteins may play a pivotal role in pathogenies. Future studies would allow us to better understand how the interplay between cellular metabolic function might be used in future PD treatments.

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