The Role of Thionine on Amyloid Precursor Protein Processing in N2a-APPSwe Cells

Alzheimer's disease, marked by aberrant accumulation of amyloid-β (Aβ) peptides produced by the cleavage of amyloid precursor protein (APP) by secretases, is associated with cognitive impairment. Evidence has shown that cholinergic activity may alter the management of APP processing. The objective of this investigation was to assess the effect of thionine (TH), a phenothiazine-structured cholinesterase inhibitor, on the processing of APP in N2a mouse neuroblastoma cells that overexpress the Swedish mutant of APP (N2a/APPSwe cells). To this end, we investigated how TH affects levels of Aβ40/42 peptides, soluble APPα (sAPPα), intracellular APP, β-site APP-cleaving enzyme 1 (BACE-1), presenilin-1 (PS1), and glycogen synthase kinase 3 beta (GSK3β). After treating N2a/APPSwe cells with TH at concentrations of 1.25-10 μM for 24 h, the levels of Aβ42, Aβ40 and sAPPα were evaluated using ELISA. In addition, the effects of thionine on intracellular APP, PS1 and GSK3β levels were analyzed by Western blotting. Our findings showed that thionine significantly reduced the levels of Aβ peptides and APP in N2a/APPSwe cells. When we evaluated the effects of thionine on APP processing, no significant alteration was detected in the level of BACE-1. However, a statistically significant reduction was observed in the levels of PS1 and GSK3β. The results provide an important mechanism of action for thionine's potential to prevent amyloid pathology.