Elsevier

Neuroscience

Volume 114, Issue 1, 18 September 2002, Pages 265-273
Neuroscience

Characterization of neuronal dystrophy induced by fibrillar amyloid β: implications for Alzheimer’s disease

https://doi.org/10.1016/S0306-4522(02)00241-5Get rights and content

Abstract

Amyloid deposition, neuronal dystrophy and synaptic loss are characteristic pathological features of Alzheimer’s disease (AD). We have used cortical neuronal cultures to assess the dystrophic effect of fibrillar amyloid β (Aβ) and its relationship with neurotoxicity and synaptic loss. Treatment with fibrillar Aβ led to the development of neuritic dystrophy in the majority of the neurons present in the culture. Morphometric analysis and viability assays showed that neuronal dystrophy appeared significantly earlier and at lower Aβ concentrations than neurotoxicity, suggesting that both effects are generated independently by different cellular mechanisms. The development of dystrophic features required Aβ fibril formation and did not depend on the presence of the RHDS adhesive domain in the sequence of Aβ. Finally, a dramatic reduction in the density of synaptophysin immunoreactivity was closely associated with dystrophic changes in viable neurons.

These results suggest that aberrant plastic changes and loss of synaptic integrity induced by fibrillar Aβ may play a significant role in the development of AD pathology.

Section snippets

Primary neuronal cultures

Rat cortical cultures were established from embryonic day 17 fetuses as described (Busciglio et al., 1993). The cells were plated on poly-L-lysine-coated dishes or glass coverslips at a density of 10 000 cells/cm2 in Dulbecco’s modified Eagle’s medium (DMEM) plus 10% horse serum for 2 h. The medium was then replaced with DMEM plus a 1:1 mixture of N2 and B27 supplements (Gibco BRL).

Aβ treatment

Peptide treatments were performed as previously described (Busciglio et al., 1995, Pigino et al., 2001). In brief,

Characterization of Aβ-induced neuronal dystrophy

Cortical neurons were treated with 20 μM fibrillar Aβ from days 5 to 9 in culture and the development of neuronal dystrophy was analyzed starting at day 1 after the initiation of the treatment. The cultures were fixed at the indicated time points, immunostained with an antibody against the neuronal-specific protein β-tubulin class III, and analyzed by immunofluorescence microscopy. Neuronal cells were placed in three categories according to the degree of dystrophy: non-dystrophic, mildly

Discussion

The characterization of the cellular and molecular mechanisms leading to neuronal dysfunction in AD is essential for the development of effective therapies. These experiments demonstrate that treatment of cortical neurons with low micromolar concentrations of fibrillar Aβ induces neuritic dystrophy without affecting neuronal viability. At higher Aβ concentrations, close to 80% of the neurons in the culture exhibit dystrophic features after 4 days of incubation with fibrillar Aβ (Fig. 3). The

Acknowledgements

Supported by grants from the University of Connecticut Health Center, the Alzheimer’s Association and NIH (HD38466) to J.B.

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