Astemizole, a Second-Generation Histamine H1-Receptor Antagonist, Did Not Attenuate the Aggregation Process of α-Synuclein In Vitro

The antihistamine astemizole has shown disease-modifying effects in several preclinical disease models of Parkinson's disease (PD). Astemizole also interacts with an anomalous aggregation of Alzheimer's disease-related amyloid-β (Aβ) peptide and has inhibitory activity on the human prion protein PrP . We hypothesized that the proposed preclinical benefits of astemizole on PD can be associated with the attenuation of pathological α-synuclein (α-syn) aggregation. We tested the effects of astemizole on the fibrillation processes of amyloid peptides using thioflavin T aggregation monitoring, Congo red spectral analysis, cell viability study, and transmission electron microscopic imaging. We found that astemizole did not inhibit α-syn aggregation in vitro even at a high molar ratio but inhibited the assembly of Aβ aggregates. Our results suggest that the inhibitory effect of astemizole on amyloid formation is target-protein selective, and the proposed beneficial effects of this compound observed in translational PD models might not be due to its ameliorating effects on α-syn aggregation.