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

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 (A beta P), although the mechanisms of A beta P toxicity are poorly understood. A beta P1-40 is the most prevalent A beta P present in the neuronal and non-neuronal tissues from SAD patients. A beta P1-40 toxicity has been examined mainly after prolonged incubation and correlates with the age and fibrillar morphology of A beta P1-40. Globular and nonfibrillar A beta Ps 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 A beta P1-40 on cultured, aged human, AD-free fibroblasts. AFM images show that freshly prepared A beta P1-40 in phosphate-buffered saline (PBS) are globular and do not form fiber for an extended time period. A beta P1-40 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 A beta P1-40-induced degeneration was prevented by anti-A beta P antibody, zinc, and Tris, but not by tachykinin neuropeptides. In Ca2+-free extracellular medium, A beta P1-40, did not induce cellular degeneration. In the presence of extracellular Ca2+, A beta P1-40 induced a sustained increase in the cellular Ca2+. Thus, short-term and acute A beta P1-40 toxicity is mediated by Ca2+ uptake, most likely via calcium-permeable A beta P 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 beta protein(1-40) induces rapid cellular degeneration in aged human fibroblasts: evidence for A beta P-channel-mediated cellular toxicity.