Session Title: Inflammation
MICROGLIAL UPTAKE OF AMYLOID-ß AND INFLAMMATORY ACTIVITY ARE DETERMINED BY AMYLOID-ß AGGREGATION STATE AND EXPRESSION OF INNATE IMMUNITY RECEPTORS
R. Schomburg, K. Faßbender
Oligomers are believed to be the most neurotoxic aggregation state of the amyloid-ß (Aß) peptide. The process leading to this neurotoxicity is not yet fully understood, but inflammation is known to play a critical role in the pathogenesis of Alzheimer's disease. CD14, TLR2 and TLR4 have been reported to contribute to a proinflammatory microglial response upon exposure to aggregated Aß species, however, no distinction between oligomers and fibrils has been made in these studies. In this study, we produced distinct Aß aggregates (i.e. oligomers and fibrils), and characterized them by Western blot and electron microscopy. Our data demonstrates the direct binding of oligomeric or fibrillar Aß species to CD14, TLR2 and TLR4 at nanomolar concentrations in HEK cells overexpressing these receptors. Furthermore we quantified the uptake of oligomers and fibrils at low nanomolar concentrations confirming that oligomers are preferentially taken up by primary microglia and a monocytic cell line. We demonstrated by real-time PCR, ELISA and Western blot that the inflammatory microglial response to Aß is dependent on its conformational state (oligomeric or fibrillar). The modulatory role of TLR2, TLR4 and CD14 in this process has also been examined via knockout microglia as well as by using blocking antibodies. This work demonstrates the importance of Aß peptide structure regarding microglial activation.