Production of β-amyloid by primary human foetal mixed brain cell cultures and its modulation by exogenous soluble β-amyloid

Abstract

Previous studies on β-amyloid production have been carried out using transfected cells and cell lines. We measured the 40 and 42 amino acid forms of β-amyloid released into the culture medium by primary human foetal mixed brain cell aggregate culture over 3 months. In this model, neurones and supporting cells are maintained in serum-free defined medium. The secretion of significant amounts of β-amyloid 40 and 42 was observed throughout culture for three separate cultures. Levels of β-amyloid 40 and 42 closely followed the neuronal content of the cultures as estimated by cellular neurone-specific enolase. Addition of synthetic β-amyloid 1-40 to the cultures for 1 week at 35 days in vitro resulted in a dose-related reduction in cellular neurone-specific enolase levels. Primary human aggregate brain cell cultures produced multimeric β-amyloid, as determined by immunoassay. β-Amyloid-treated cultures released diminishing amounts of multimeric β-amyloid and contained increasing amounts of intracellular multimeric β-amyloid with increasing exogenous β-amyloid. These results suggest that release of multimeric β-amyloid into the extracellular environment by human primary neurones can be affected by the presence of extracellular β-amyloid. This has implications for Alzheimer’s disease in that β-amyloid released into the extracellular environment by dead/dying neurones could modulate β-amyloid release by surrounding neurones, potentially causing amplification of toxicity. Moreover, intracellular β-amyloid oligomer-dependent neurotoxicity may be a component of neurodegeneration in Alzheimer’s disease, and other conditions with increased β-amyloid synthesis, suggesting anti-amyloid therapies for Alzheimer’s disease may have to target intracellular β-amyloid.