Analysis of microdissected human neurons by a sensitive ELISA reveals a correlation between elevated intracellular concentrations of Abeta42 and Alzheimer's disease neuropathology.

In Alzheimer's disease (AD), Purkinje neurons in the cerebellum are spared, while, for instance, pyramidal neurons in the hippocampus are neuropathologically affected. Several lines of evidence suggest that the pathogenesis could be induced by the concentration-dependent polymerization of the amyloid beta-peptide (Abeta) into extracellular oligomers. The role of intracellular Abeta is not fully investigated, but recent data indicate that also this pool could be of importance. Here, we use laser capture microdissection microscopy for isolation of Purkinje neurons from AD cases and controls, and quantify the low levels of intracellular Abeta using a novel and highly sensitive ELISA. Similar to Cornu Ammonis 1 pyramidal neurons, the intracellular levels of the most toxic variant, Abeta42, as well as the Abeta42/Abeta40 ratio, were increased in Purkinje neurons from sporadic AD cases as compared to controls. However, the levels of Abeta42 as well as Abeta40 were clearly lower in Purkinje neurons than in pyramidal neurons. Based on the volume of the captured Purkinje neurons, the intraneuronal concentrations of Abeta42 were calculated to be 200 nM in sporadic AD cases and 90 nM in controls. The corresponding concentrations in pyramidal neurons from hippocampus were 3 muM and 660 nM, respectively. The Abeta40 concentration was not significantly altered in AD cases compared to controls. However, we found ten times higher concentration of Abeta40 in pyramidal neurons (10 muM) compared to Purkinje neurons (1 muM). Finally, we suggest that high concentration of intracellular Abeta42 correlates with vulnerability to AD neuropathology.