Purpose: Oxidative stress is a hallmark of Alzheimer's Disease (AD) and promotes tau phosphorylation. Since Thioredoxin Interacting protein (TXNIP), the inhibitor of the anti-oxidant system of Thioredoxin, is up regulated in the hippocampus of AD patients, we investigated whether TXNIP plays a role in promoting tau phosphorylation and whether Verapamil, an inhibitor of TXNIP expression, prevents TXNIP downstream effects.
Methods: We analyzed TXNIP expression and tau phosphorylation in the hippocampus of the 5xFAD mice in the absence and presence of a pharmacological treatment with Verapamil. Using SH-SY5Y cells, we verified the causative role of TXNIP in promoting tau phosphorylation at Ser202/Thr205, by inducing TXNIP silencing.
Results: The amyloid beta peptide (Aβ1-42) leads to TXNIP over-expression in SH-SY5Y cells, which in turns induces oxidative stress and the activation of p38 MAPK, promoting tau phosphorylation at Ser202/Thr205. Silencing of TXNIP abolishes Aβ1-42-induced tau phosphorylation, p38 MAPK phosphorylation and subsequent tau phosphorylation. Verapamil prevents TXNIP expression as well as p38 MAPK and tau phosphorylation at Ser202/Thr205 in the hippocampus of the 5xFAD mice.
Conclusions: Our study unveil a novel pathway involved in AD progression that is inhibited by Verapamil, shedding new light on the understanding of the therapeutic potential of Verapamil in AD.
Keywords: Alzheimer’s disease; Neuron; Oxidative stress; TXNIP; Tau phosphorylation; Verapamil; p38 MAPK.