Fresh and nonfibrillar amyloid β protein(1–40) induces rapid cellular degeneration in aged human fibroblasts: evidence for AβP‐channel‐mediated cellular toxicity

ABSTRACT Alzheimer's disease (AD) is primarily nonfamilial or sporadic (SAD) in origin, although several genetic linkages are reported. Tissues from AD patients contain fibrillar plaques made of 39 to 43 amino acid‐long amyloid beta peptide (AβP), although the mechanisms of AβP toxicity are poorly understood. AβP1–40 is the most prevalent AβP present in the neuronal and non‐neuronal tissues from SAD patients. AβP1–40 toxicity has been examined mainly after prolonged incubation and correlates with the age and fibrillar morphology of AβP1–40. Globular and nonfibrillar AβPs are released continually during normal cellular metabolism; they elevate cellular Ca2+ and form cation‐permeable channels. However, their role in cellular toxicity is poorly understood. We have used an integrated atomic force and light fluorescence microscopy (AFM‐LFM), laser confocal microscopy, and calcium imaging to examine real‐time and acute effect of fresh and globular AβP1–40 on cultured, aged human, AD‐free fibroblasts. AFM images show that freshly prepared AβP1–40 in phosphate‐buffered saline (PBS) are globular and do not form fiber for an extended time period. AβP1–40 induced rapid structural modifications, including cytoskeletal reorganization, retraction of cellular processes, and loss of cell‐cell contacts, within minutes of incubation. This led to eventual cellular degeneration. AβP1–40‐induced degeneration was prevented by anti‐AβP antibody, zinc, and Tris, but not by tachykinin neuropeptides. In Ca2+‐free extracellular medium, AβP1–40 did not induce cellular degeneration. In the presence of extracellular Ca2+, AβP1–40 induced a sustained increase in the cellular Ca2+. Thus, short‐term and acute AβP1–40 toxicity is mediated by Ca2+ uptake, most likely via calcium‐permeable AβP pores. Such rapid degeneration does not require fibrillar plaques, suggesting that the plaques may not have any causative role.—Zhu, Y. J., Lin, H., Lal, R. Fresh and nonfibrillar amyloid β protein(1–40) induces rapid cellular degeneration in aged human fibroblasts: evidence for AβP‐channel‐mediated cellular toxicity. FASEB J. 14, 1244–1254 (2000)