Pan-SHIP1/2 inhibitors promote microglia effector functions essential for CNS homeostasis

Abstract

We show here that both SHIP1 and its paralog SHIP2 are expressed at the protein level in microglia. To examine whether targeting of SHIP paralogs might influence microglial physiology and function we tested the capacity of SHIP1-selective, SHIP2-selective and pan-SHIP1/2 inhibitors for their ability to impact microglia proliferation, lysosomal compartment size and phagocytic function. We find that highly potent pan-SHIP1/2 inhibitors can significantly increase lysosomal compartment size and phagocytosis of dead neurons and Aβ1–42 by microglia in vitro. We show that one of the more potent and water-soluble pan-SHIP1/2 inhibitors, K161, can penetrate the blood-brain barrier and consistent with this K161 increases the capacity of CNS-resident microglia to phagocytose beta-amyloid and apoptotic neurons following systemic administration. These findings provide the first demonstration that small molecule modulation of microglia function in vivo is feasible and suggest the possibility that dual inhibition of the SHIP1 and 2 paralogs could provide a novel means to enhance basal microglial homeostatic functions for therapeutic purposes in Alzheimer's Disease, and possibly other dementias where increased microglial function could be beneficial.