C-Reactive Protein Induces Tau Hyperphosphorylation via GSK3β Signaling Pathway in SH-SY5Y Cells

Amyloid plaques and neurofibrillary tangles are the key pathological features of Alzheimer's disease (AD). Studies have shown that C-reactive protein (CRP) increases during inflammatory reactions and, therefore, has been associated with AD. However, there is no published report relating the impact of CRP to the regulation of tau phosphorylation. In the present study, we investigated the effects of CRP on the phosphorylation of tau protein in SH-SY5Y cells. Treatment of cells with CRP (5, 10, 20 μg/ml) resulted in neurotoxicity and apoptosis, as was observed by MTT assay and Hoechst staining, respectively. Western blot analysis showed that CRP, in a time- and concentration-dependent manner, induced the phosphorylation of tau at Ser202 and ser396 in SH-SY5Y cells. Phosphorylation of Akt (Ser473) and GSK3β (Ser9) were decreased by CRP treatment, whereas phosphorylation of ERK and p38 were not affected. Pharmacological inhibition of GSK3β reversed the effects induced by CRP, viz., cytotoxicity, apoptosis, and tau phosphorylation. Herein, we present a novel mechanism of cell death following CRP insult, which activates tau hyperphosphorylation by regulating GSK3β activity. CRP could potentially be used as an important pathological factor for the therapeutic intervention of AD.