Longevity & AgingMicroglial Activation Unlocks Amyloid's Power to Drive Astrocyte Reactivity in Alzheimer's
Alzheimer's disease involves more than amyloid and tau; brain immune cells appear to shape how the disease unfolds. This study used PET imaging and blood and spinal fluid markers in 101 older adults, plus a 251-person confirmation sample, to ask whether activated microglia influence how amyloid affects astrocytes. Amyloid burden was linked to higher plasma GFAP, a marker of astrocyte reactivity, only in people with microglial activation. This held across cortical regions and with two different microglial markers (TSPO PET and CSF sTREM2). In people with activated microglia, the amyloid-astrocyte pathway was also tied to higher p-tau217, more tau tangles on PET, and worse cognition. The findings are cross-sectional and cannot prove causation, but they suggest glial cells could be therapeutic targets.
