Soluble Aβ induces prolonged efflux of K⁺ in Tg2576 cortical neurons.

<p>Treatment with 1 µM Aβ_1-40 triggered rapid efflux of K⁺ from Tg2576 neurons (A), which continued over the 120 minutes of recording. Aβ_1-40 treatment caused a rapid influx of H⁺ in Tg2576 neurons (B), which did not stabilise over the 120 minute recording period.</p

Uptake of soluble Aβ by wildtype and Tg2576 cortical neurons <i>in vitro</i>.

<p>Wildtype and Tg2576 cortical neurons were treated with 10 µM of monomeric Aβ_1-40, and immunostained for Aβ after 24 hours. In untreated Tg2576 neurons, Aβ was smoothly distributed throughout the cytoplasm and processes of all neurons (A). When Aβ_1-40 was applied to wildtype neurons, it was internalised and distributed in a punctate manner within the cytoplasm and processes (B). Notably, not all wildtype neurons internalised Aβ_1-40 (B). When Aβ_1-40 was applied to Tg2576 neurons, both smooth and punctately distributed Aβ was detected within neurons (C). scale bar  = 25 µm.</p

Tg2576 cortical neurons are more vulnerable to soluble Aβ-induced neurotoxicity.

<p>Wildtype and Tg2576 cortical neurons were treated daily with 1 µM (A) or 10 µM (B) of monomeric Aβ_1-40 for 6 days, and neuronal viability (intracellular metabolism as assessed by Alamar Blue assay) assessed every 24 hours. At 1 µM concentrations, only Tg2576 neurons were vulnerable to Aβ_1-40, resulting in approximately 30% cell death after 6 days (A). 10 µM Aβ_1-40 was mildly toxic to wildtype neurons over the experimental timecourse, but killed 40% of Tg2576 neurons after 6 days (B). The Alamar Blue neurotoxicity assay produced similar results to direct counting of dying cells via propidium iodide uptake following treatment with 10 µM Aβ_1-40 (C). * - p<0.05, ANOVA. Error bars represent standard error values from at least three replicates per experimental condition. This graph is representative of the results observed from 4 different experiments.</p

Soluble Aβ triggers caspase-3 expression in Tg2576 cortical neurons.

<p>Tg2576 neurons cultured for 14 days <i>in vitro</i> (DIV) showed no signs of caspase-3 activation (A). However, when 7 DIV Tg2576 neurons were treated with 1 µM Aβ_1-40 daily for 6 days, a substantial number of neurons were found to express caspase-3 (B).</p

Soluble Aβ causes disruptions in tau distribution in Tg2576 cortical neurons.

<p>Tau immunolabelling of the axonal cytoskeleton demonstrated that axonal morphology was similar between wildtype (A) and Tg2576 (B) cortical neurons over 7–14 DIV. Six daily 1 µM Aβ_1-40 treatments of 7DIV wildtype neurons had no discernible effect upon axonal morphology (C). However, substantial changes in tau-labelling were observed in Aβ_1-40 treated Tg2576 neurons (D); including increased intensity of tau immunostaining after 24 hours, followed by blebbing and axonal fragmentation which worsened after four days of treatment (D). Furthermore, after four consecutive days of 1 µM Aβ_1-40 treatment a number of axonal swellings, with dense accumulations of hyperphosphorylated tau, were observed in Tg2576 neuron cultures (E). scale bars  = 30 µm (A–D), 15 µm (E).</p