Dimethyl Fumarate Mitigates Tauopathy in Aβ-Induced Neuroblastoma SH-SY5Y Cells

Alzheimer's disease pathogenesis is measured by two key hallmarks viz extracellular senile plaques composed of insoluble amyloid beta (A beta) and neurofibrillary tangles composed of hyperphosphorylated tau, resulting in microtubule destabilization, synaptic damage and neurodegeneration. Accumulation of A beta is an introducing pathological incident in Alzheimer's disease; hence, the effect of dimethyl fumarate (DMF) on A beta(1-42)-induced alterations in phosphorylated tau, related protein kinases, fibrillogenesis and microtubule assembly in neuroblastoma SH-SY5Y cells was determined. DMF attenuated A beta(1-42)-induced neuronal apoptosis by down-regulating protein levels of Bcl-2/Bax, cleaved caspase-3 and caspase-9. A beta(1-42)-induced upsurge in tau phosphorylation at Ser396 and Thr231 epitopes was found to be declined by DMF pretreatment. The upregulated activity of glycogen synthase kinase-3 beta (GSK-3 beta) by A beta(1-42) treatment was blocked by DMF pretreatment. PI3K substrate Akt (at Ser473) as well as Wnt dependent beta-catenin and cyclin D1 activity was found to be upregulated by DMF pretreatment in A beta(1-42) treated cells. ThT fluorescence and MTT assay showed that DMF reduces A beta fibrillogenesis and inhibit related cytotoxicity. Also, DMF exerts a protective effect on A beta(1-42)-induced microtubule disassembly caused due to a reduction in polymerized beta 3-and alpha-tubulin. These results indicate that down-regulation of GSK-3 beta activity and subsequent activation of PI3K/Akt and Wnt/beta-catenin signaling pathways are closely involved in the shielding effect of DMF against A beta(1-42)-induced tau hyperphosphorylation. Modulating cellular events related to A beta(1-42)-induced tau hyperphosphorylation, aggregation and microtubule stabilization offers new molecular insights into the defensive outcome of DMF towards appropriate management for Alzheimer's disease.