Astrocyte-derived lactoferrin reduces -amyloid burden by promoting the interaction between p38 kinase and PP2A phosphatase in male APP/PS1 transgenic mice

Background and Purpose: Overexpression of astrocytic lactoferrin (Lf) was observed in the brain of Alzheimer's disease (AD) patients, whereas the role of astrocytic Lf in AD progression remains unexplored. In this study, we aimed to evaluate the effects of astrocytic Lf on AD progression. Experimental Approach: Male APP/PS1 mice with astrocytes overexpressing human Lf were developed to evaluate the effects of astrocytic Lf on AD progression. N2a-sw cells also were employed to further uncover the mechanism of astrocytic Lf on beta-amyloid (A beta) production. Key Results: Astrocytic Lf overexpression increased protein phosphatase 2A (PP2A) activity and reduced amyloid precursor protein (APP) phosphorylation, A beta burden and tau hyperphosphorylation in APP/PS1 mice. Mechanistically, astrocytic Lf overexpression promoted the uptake of astrocytic Lf into neurons in APP/PS1 mice, and conditional medium from astrocytes overexpressing Lf inhibited p-APP (Thr668) expression in N2a-sw cells. Furthermore, recombinant human Lf (hLf) significantly enhanced PP2A activity and inhibited p-APP expression, whereas inhibition of p38 or PP2A activities abrogated the hLf-induced p-APP down-regulation in N2a-sw cells. Additionally, hLf promoted the interaction of p38 and PP2A via p38 activation, thereby enhancing PP2A activity, and low-density lipoprotein receptor-related protein 1 (LRP1) knockdown significantly reversed the hLf-induced p38 activation and p-APP down-regulation. Conclusions and Implications: Our data suggested that astrocytic Lf promoted neuronal p38 activation, via targeting to LRP1, subsequently promoting p38 binding to PP2A to enhance PP2A enzyme activity, which finally inhibited A beta production via APP dephosphorylation. In conclusion, promoting astrocytic Lf expression may be a potential strategy against AD.