ApoE secretion by NGF-treated U373 cells provides neuroprotection from oxidative stress. (A) Representative scheme of astrocyte–neuron co-cultures set up as described in the Materials and Methods Section. Neurite-bearing cells, neurite length, and cell number were assessed 48 h after the establishment of co-culture. (B) Representative images in bright field and quantitative assessment of neuronal morphology of N1E-115 cells, previously treated (+) or not (−) with rotenone (0.1 µM) for 16 h. N1E-115 were then kept in fresh DMEM (Ctrl), or co-cultured with control U373 (U373-Ctrl), NGF-pre-treated U373 (U373-NGF), and NGF-pre-treated U373 silenced for ApoE (U373-NGF ApoE siRNA) for 48 h. n = 5 different experiments. Data represent means ± SD. Statistical analysis was carried out by using one-way ANOVA, followed by Tukey’s post hoc test. * p < 0.05, ** p < 0.01, *** p < 0.001.