IL-8 and MCP-1 Impact on Tau Phosphorylation and Phosphatase Activity

Background: Chronic inflammation is a feature of Alzheimer's disease (AD), resulting in excessive production of inflammatory mediators that can lead to neuroinflammation, contributing to alterations in A beta production and deposition as Senile Plaques (SPs), and to neurofibrillary tangles (NFTs) formation, due to hyperphosphorylated Tau protein. Objective: This work addressed the impact of the interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), two chemokines, on Tau phosphorylation; and also evaluated the chemokines' levels in plasma using samples from a regional cohort. Methods: Human neuronal SH-SY5Y cells exposed to IL-8 and MCP-1 chemokines were monitored for their protein and phosphorylated protein levels by western blotting analysis. A serine/threonine protein phosphatase (PPs) activity assay was employed to monitor PPs activity. Subsequently, flow cytometry was used to monitor chemokines levels in plasma samples from individuals with cognitive deficits. Results: Chemokines' exposure resulted only in minor cytotoxicity effects on SH-SY5Y, and in increased Tau phosphorylation, particularly at the S396 residue. Tau phosphorylation correlated with PPs inhibition and was consistent with GSK3 beta phosphorylation-mediated inhibition. Subsequent analysis of plasma from individuals with cognitive deficits showed that IL-8 levels were decreased. Conclusion: Data shows that both chemokines tested can exert an effect on GSK3 beta phosphorylation and modulate PPs activity, potentially resulting in increased Tau phosphorylation and subsequent NFTs formation. One can deduce that increased chemokines stimulation during chronic inflammation can exacerbate this event. The work contributes to a better understanding of the mode of action of these chemokines on AD pathogenesis and opens novel research avenues.