Enhanced Aβ1-40 Production in Endothelial Cells Stimulated with Fibrillar Aβ1-42

Amyloid accumulation in the brain of Alzheimer's patients results from altered processing of the 39- to 43-amino acid amyloid beta protein (A beta). The mechanisms for the elevated amyloid (A beta(1-42)) are considered to be over-expression of the amyloid precursor protein (APP), enhanced cleavage of APP to A beta, and decreased clearance of A beta from the central nervous system (CNS). We report herein studies of A beta stimulated effects on endothelial cells. We observe an interesting and as yet unprecedented feedback effect involving A beta(1-42) fibril-induced synthesis of APP by Western blot analysis in the endothelial cell line Hep-1. We further observe an increase in the expression of A beta(1-40) by flow cytometry and fluorescence microscopy. This phenomenon is reproducible for cultures grown both in the presence and absence of serum. In the former case, flow cytometry reveals that A beta(1-40) accumulation is less pronounced than under serum-free conditions. Immunofluorescence staining further corroborates these observations. Cellular responses to fibrillar A beta(1-42) treatment involving eNOS upregulation and increased autophagy are also reported.