GFAP reactivity, apolipoprotein E redistribution and cholesterol reduction in human astrocytes treated with α-synuclein

Alpha-synuclein (alpha-syn) is an abundant neuronal protein expressed at the synapse. In neurodegenerative disease alpha-syn accumulates in the extracellular space. Astrocytes present at neural synapses are thought to contribute to synaptogenesis through cholesterol release and normally exhibit increased glial fibrillary acid protein (GFAP) reactivity and apolipoprotein E (apoE) expression in neurodegenerative disease states. We proposed that extracellular alpha-syn treatment of human astrocytes would impact cholesterol levels and expression of GFAP and apolipoprotein E (apoE). Human astrocytes were treated with alpha-syn at different concentrations and time points to determine the effective membrane permeability of the peptide. After alpha-syn treatment, we analyzed apoE and cholesterol levels in the astrocyte membrane. Lastly, we performed immunocytochemistry for GFAP in control and alpha-syn treated cells. Our results indicate membrane apoE was reduced and redistributed from a nuclear and membranous dominated expression to the cytosol. Cholesterol levels were also reduced in the astrocyte cell membrane. GFAP expression was sharply increased in alpha-syn treated cells indicating that alpha-syn may contribute to reactive gliosis. Our results support the conclusion that astrocytes play a role in pathological mechanisms in synucleinopathies.