P1-144: Oligomeric Abeta increases tween 20-insoluble MTT in cultured neuroblastoma and myoblast cells

Abstract

Alzheimer's Disease (AD) and Inclusion Body Myositis (IBM) are two chronic degenerative diseases that strike the brain and skeletal muscle respectively. Although the affected cell types differ, these two diseases share a number of similarities: age of onset, tissue wasting, and the accumulation of the beta-amyloid peptide (Aβ). This peptide is widely believed to play a role in the degeneration of AD as well as IBM, though the similarity of its role remains to be established. We tested the effect of size-fractionated soluble oligomeric Aβ(1–42) for its effect on neuroblastoma and myoblast cell lines. Synthetic Aβ(1–42) was assembled under conditions where fibrils are not formed. The resultant mixture of oligomers and monomers was fractionated by size exclusion chromatography. Equal amounts of Aβ as determined by ELISA in pooled fractions containing oligomers or monomers, as well as separately produced fibrils were applied to SH-SY5Y neuroblastoma or C2C12 myoblast cell cultures. Oligomeric but not monomeric or fibrillar Aβ increased Tween-20 insoluble MTT (iMTT) production without affecting the Tween-20 soluble fraction in a short-term inclubation with both SH-SY5Y and C2C12 cells. In addition to providing a positive signal, the increase in iMTT required 10–20 fold less Aβ to achieve a 50% effect than the unfractionated (oligomers + monomers). Similar results were observed for size-fractionated Aβ in media conditioned by H4 neuroglioma cells overexpressing the amyloid precursor protein. These results suggest that a fundamental property of the conformation/configuration of the Aβ peptide rather than an effect of biological processing is responsible for the biological events leading to the accumulation of the iMTT fraction. The increase in iMTT also correlates with total cell death after longer-term exposure to Aβ, consistent with the hypothesis that oligomeric Aβ is the toxic form in these two related diseases. Funded by Alzheimer's Association IIRG-06–27275.