Context-dependent toxicity of amyloid-β peptides on mouse cerebellar cells

Alzheimer's disease (AD) is the major cause of dementia in old people. AD pathology is characterized by amyloid-β (Aβ) deposits in several regions of the brain, and links have been hypothesized between Aβ toxicity and apoptosis. Cerebellar granule cells (CGCs) have been widely used as in vitro tools for molecular studies correlating apoptosis with AD, although the cerebellum is a relatively spared area of the brain in vivo. We have used mixed neuronal-glial cerebellar cultures (NGCCs) and organotypic cerebellar cultures (OCCs) obtained from postnatal mice to assess the toxic effect of the Aβ oligomer 1-40 (Aβ1-40) after propidium iodide uptake in vitro. Our results demonstrate that NGCCs, which are primarily composed of CGCs, are resistant to Aβ1-40 challenge (5-10 μM) when cultured in physiological (5 mM) extracellular KCl ([K+]e) concentrations, i.e., in a condition in which CGCs undergo full maturation. Conversely, when 10 μM Aβ1-40 is given to NGCCs cultured in elevated (25 mM) [K+]e (and thus maintained in an immature state), there is a statistically significant increase in cell death. Cell death is by apoptosis, as demonstrated by ultrastructural examination. OCCs are resistant to Aβ challenge in any of the conditions tested (variation of [K+]e, presence or absence of serum, or addition of the neprilysin blocker phosphoramidon). Altogether these observations lead us to conclude that cerebellar cells in an organotypic context may be less susceptible to damage by Aβ, raising the question whether isolated CGCs are a reliable assay in drug discovery studies of AD.