beta-Amyloid peptide induced cytoskeletal reorganization in cultured astrocytes

The effects of beta-amyloid (25-35) (betaA) on cultured astrocytes from rat cortex were studied and compared with those of a scrambled peptide and with untreated cultures. Single addition (from 5 to 200 microg/ml) of betaA peptide induced a marked morphological change in astrocytes, changing their flat polygonal shape into stellate process-bearing morphology. The changes induced by betaA were concentration and time-dependent. The addition of the scrambled peptide did not alter cell viability in comparison with untreated astrocyte cultures. However, cell viability was dose-dependently decreased by betaA. A subpopulation of betaA-treated astrocytes showed an increase in glial fibrillary acidic protein (GFAP) and Vimentin (Vim) immunostaining while other reactive astrocyte markers such as S100beta, MAP2, and ApoE remained unaltered or undetectable. The morphological changes in betaA-treated astrocytes appeared to be mainly due to a cytoskeletal reorganization, since the total amounts of GFAP and Vim proteins were not essentially modified. These results strongly suggest that astrocytes are another cellular target of the effects of betaA and this may be relevant to understanding the neuropathology of Alzheimer's disease.