Webers, Alessandra: Neuroinflammation, microglia and the cell biology of Alzheimer's Disease. - Bonn, 2020. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn, University of Melbourne.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-57820
@phdthesis{handle:20.500.11811/8332,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-57820,
author = {{Alessandra Webers}},
title = {Neuroinflammation, microglia and the cell biology of Alzheimer's Disease},
school = {{Rheinische Friedrich-Wilhelms-Universität Bonn} and {University of Melbourne}},
year = 2020,
month = apr,

note = {The pathology of Alzheimer’s disease (AD) is characterised by progressive accumulation of misfolded proteins, which form senile plaques and neurofibrillary tangles, and chronic inflammation in the brain associated with inflammatory mediators by the activation of innate immune responses. There has been considerable interest in the role of neuroinflammation in directly contributing to the progression of AD. Studies in mice and humans have identified a role for microglial cells, the resident innate immune cells of the CNS, in AD. Activated microglia are a key hallmark of the disease and the secretion of pro-inflammatory cytokines by microglia may result in a positive feedback loop between neurons and microglia, resulting in ongoing low-grade inflammation and associated neurotoxicity. The underlying mechanisms however are poorly understood. Here the role of microglia was investigated, especially their link to ApoE – the strongest risk factor for late onset Alzheimer’s disease – and the relationship between microglia, neurons and neuroinflammation.
Target replacement mice were used, where the human ApoE2, ApoE3 or ApoE4 allele replaces the mouse ApoE allele. Microglia were activated in a two- step setup. Initially cells were primed with LPS, followed by a secondary stimulus, such as ATP or Aβ. The system was used to characterise the cytokines secreted by activated microglia and to assess the impact of conditioned medium from stimulated and Aβ treated microglia on neuronal morphology.
The first results Chapter (Chapter 3) established the system – mouse microglia were isolated from brains of neonatal mice and characterised by CD11b staining. Microglia from all three ApoE genotypes were directly compared and the data from ELISA and mass spectrometry revealed an enhanced pro- inflammatory response by ApoE4 microglia and the least efficient at internalizing amyloid β.
Chapter 4 analysed the impact of conditional medium from the microglia ApoE variants on neurons and the results showed an ApoE-dependent effect on dendrite morphology. Conditioned media from immunostimulated and Aβ microglia were incubated with cortical neurons from wt animals. Both the dendrite length and number of dendrites were significantly reduced in neurons treated with conditioned medium from ApoE4 microglia.
TNFα was identified as a major cytokine and was responsible for modifying neuron morphology in cell assays. Neutralising the cytokine, with an anti-TNFα antibody abrogated the majority of morphological changes induced by the conditioned media from activated microglia. Hence the data suggests that TNFα may have a major role in mediating neuroinflammation.
The third results Chapter (Chapter 5) compared aspects of macrophage function with microglia. Here it was shown, that microglia do not require SNX5 for macropinocytosis, and most likely utilise peripheral mediated macropinocytosis as the main form of macropinocytic internalisation. A major finding was the ability of sodium chloride to augment a pro-inflammatory response not only by immunostimulated macrophages by also microglia. Inhibition of the p38 MAPK signalling pathway partially ameliorated the NaCl- induced inflammatory responses in both macrophages and microglia, together with high levels of secreted IL-1β, indicating activation of the NLRP3 inflammasome.
Overall the studies highlight a role for ApoE4 allele to promote an enhanced inflammatory response by microglia cells.},

url = {http://hdl.handle.net/20.500.11811/8332}
}

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