High content screen microscopy analysis of Aβ1–42-induced neurite outgrowth reduction in rat primary cortical neurons: Neuroprotective effects of α7 neuronal nicotinic acetylcholine receptor ligands

β-Amyloid peptide 1–42 (Aβ1–42) is generated from amyloid precursor protein (APP) and associated with neurodegeneration in Alzheimer's disease (AD). Aβ1–42 has been shown to be cytotoxic when incubated with cultured neurons. However, APP transgenic mice over-expressing Aβ1–42 do not show substantial loss of neurons, despite deficits in learning and memory. It is thus emerging that Aβ1–42-induced memory deficits may involve subtler neuronal alternations leading to synaptic deficits, prior to frank neurodegeneration in AD brains. In this study, high content screen (HCS) microscopy, an advanced high-throughput cellular image processing and analysis technique, was utilized in establishing an in vitro model of Aβ1–42-induced neurotoxicity utilizing rat neonatal primary cortical cells. Neurite outgrowth was found to be significantly reduced by Aβ1–42 (300 nM to 30 μM), but not by the scrambled control peptide control, in a time- and concentration-dependent manner. In contrast, no reduction in the total number of neurons was observed. The Aβ1–42-induced reduction of neurite outgrowth was attenuated by the NMDA receptor antagonist memantine and the α7 nicotinic acetylcholine receptor (nAChR) selective agonist PNU-282987. Interestingly, the α7 nAChR antagonist methyllycaconitine also significantly prevented reduction in Aβ1–42-induced neurite outgrowth. The observed neuroprotective effects could arise either from interference of Aβ1–42 interactions with α7 nAChRs or by modification of receptor-mediated signaling pathways. Our studies demonstrate that reduction of neurite outgrowth may serve as a model representing Aβ1–42-mediated neuritic and synaptic toxicity, which, in combination of HCS, provides a high-throughput cell-based assay that can be used to evaluate compounds with neuroprotective properties in neurons.