P2RX7 INHIBITOR SUPPRESSES EXOSOME SECRETION, DELAYS PROTEOPATHIC TAU ACCUMULATION AND MEMORY IMPAIRMENT IN PS19 P301S TAU MICE

Abstract

P2X7 receptor (P2XR7) is an ATP-gated cation channel, highly expressed in microglia, involved in Alzheimer's disease (AD) pathobiology. Series of studies also suggested that pharmacological inhibition or genetic deletion of P2XR7 could alter exosome secretion triggered by ATP stimulation. Recently, we showed that microglia could spread tau aggregates via secretion of extracellular vesicles throughout the brain. We hypothesize that P2XR7 inhibitor could inhibit exosome secretion by microglia and thus alleviate tauopathy in PS19 P301S tau transgenic mice. Murine microglial cell line BV-2 were treated with GSK1482160, a specific inhibitor of P2X7R, prior to ATP stimulation. Culture medium were collected and exosome number was measured using Nanoparticle Tracking Analysis (NTA) and CD9 ELISA. Three-months old P301S and control wild-type mice were treated with GSK1482160 (20mg/kg) or vehicle by oral gavage for 30 days. Hippocampal dependent memory capacity was assessed and hippocampal accumulation of tau aggregation and exosomal deposition was determined by immunohistochemistry. In addition, a separated cohort of animals was generated to quantify exosome and measure hippocampal p-Tau expression by ELISA. ATP stimulation of BV-2 cells significantly increased secretion of exosomes (30-150 nm), which was significantly inhibited by GSK1482160 pre-treatment in a dose-dependent manner as determined by NTA and CD9 ELISA. GSK1482160 also restored spontaneous alteration of PS19 mice in Y-maze test, and contextual and cued fear conditioning memory as compared to vehicle-treated PS19 mice. Interestingly, hippocampal accumulation of Alz50+ and MC1+ tau aggregation was significantly reduced in GSK1482160-treated group as compared to vehicle-treated group. GSK1482160 pre-treatment successfully suppresses exosome secretion by microglia in vitro. Its oral administration also significantly reduces spatial and fear conditional memory and tau accumulation in the hippocampal region of P301S Tau mouse model.