Alpha-synuclein spreading pathology in Parkinson's disease: the influence of iron and the Rho-kinase inhibitor fasudil
by Karina Joppe
Date of Examination:2020-03-10
Date of issue:2020-06-05
Advisor:Prof. Dr. Paul Lingor
Referee:Prof. Dr. Paul Lingor
Referee:Prof. Dr. Tiago Fleming Outeiro
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http://dx.doi.org/10.53846/goediss-8016
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Abstract
English
Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease affecting approximately 1 % of the population above 60 years of age. It affects preferentially the extrapyramidal system, causing severe deficits in motor function. So far, the progression of the disease can neither be delayed nor cured. The dyshomeostasis of trace elements, especially of iron, and the presence of alpha-synuclein (α-syn) aggregate-containing Lewy bodies (LBs) in the brain are two main pathologic events playing a crucial role in PD. The underlying pathomechanisms for spreading of α-syn through the brain are still unknown, but PD-related targets such as trace elements or the rho-associated protein kinase (ROCK) were suggested to affect its aggregation pathology. Identifying triggers that affect α-syn propagation is of fundamental importance since they could be considered as auspicious targets for new therapeutic strategies. In the present study, the elemental content of nigral neurons of PD patients and control patients without neurodegeneration was analyzed using X-ray fluorescence (XRF) and it was found that intracellular element concentrations differ substantially within and between patients. Copper was the most discriminating element between the groups. On a subcellular level, X-ray diffraction revealed the presence of β-sheet protein structures in a LB, whereas XRF measurements identified a varying distribution of trace elements such as iron, selenium or copper within two LBs. Furthermore, the relation of iron and α-syn was examined. With the objective to investigate the influence of iron on α-syn propagation through the brain, a murine α-syn fibrils injection model was combined with iron intoxication and revealed reducing and redistribution effects of iron on α-syn spreading and a reduced microglia accumulation. Both iron and α-syn fibrils treatment resulted in long-term memory dysfunction in the novel object recognition test. Moreover, the influence of iron on α-syn spreading was investigated in cortical neurons using microfluidic chambers. Spreading of α-syn seemed not to be affected by iron in vitro, arguing for a more systemic mode of action in vivo. Since the ROCK inhibitor fasudil showed multiple protective effects in PD mouse models previously, we analyzed its effects on α-syn spreading in vivo. Here, the application of fasudil did not alter α-syn propagation. Taken together, the present work investigates the influence of trace elements, particularly iron, and ROCK inhibition on α-syn spreading and thus contributes to a better understanding of PD pathophysiology and to the identification of auspicious targets for new therapeutic strategies.
Keywords: alpha-synuclein; iron; Parkinson's disease; X-ray fluorescence; alpha-synuclein spreading; mouse model; X-ray