Amyloid-β peptides induce several chemokine mRNA expressions in the primary microglia and Ra2 cell line via the PI3K/Akt and/or ERK pathway

Alzheimer's disease (AD) is characterized by the presence of senile plaques composed primarily of amyloid-β peptide (Aβ) in the brain. Microglia have been reported to surround these Aβ plaques, which have opposite roles, provoking a microglia-mediated inflammatory response that contributes to neuronal cell loss or the removal of Aβ and damaged neurons. To perform these tasks microglia migrate to the sites of Aβ secretion. We herein analyzed the process of chemokine expression induced by Aβ stimulation in primary murine microglia and Ra2 microglial cell line. We found that Aβ1-42 induced the expressions of CCL7, CCL2, CCL3, CCL4 and CXCL2 in the microglia. The signal transduction pathway for the expression of CCL2 and CCL7 mRNA induced by Aβ1-42 was found to depend on phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK), whereas the pathway for CCL4 depended only on PI3K/Akt. These inflammatory chemokine expressions by Aβ stimulation emphasize the contribution of neuroinflammatory mechanisms to the pathogenesis of AD.