Figure 7.

Intracellular and extracellular Aβ are differentially modulated by PA treatment during the maturation of primary neuronal cultures. Primary neurons from TgCRND8 mice were treated with PA (100 μM, 48 h) after 1, 2, or 3 wk in culture. A) From the first week on, levels of intracellular human Aβ40 in PA-treated cells were significantly increased compared with control cells (level indicated by dotted line at 100%). B) Extracellular human Aβ40 was significantly increased by PA treatment only in mature (3-wk-old) cultures. The magnitude of the PA-induced increase in extracellular Aβ40 at that point was similar to the increase in PA-treated organotypic slice cultures (n = 3 for all groups). C) Unlike SH-SY5Y-APP cells, 1-wk-old primary neurons accumulated intracellular oAβ, even under control (C) conditions. The specificity of the oAβ signal from untreated cells was confirmed with the γ-secretase inhibitor DAPT (100 µM). The dotted line represents signal detected in cells from wild-type mice, which was equal to that obtained in cells treated with DAPT and considered background. Treatment of the primary neurons with PA produced a significant increase in RIPA-soluble intracellular oAβ (n = 4 for all groups). *P < 0.05, **P < 0.01, ***P < 0.001.