Several signaling pathways underlie astrocyte reactivity in AD, including activation of transcription 3 (JAK/STAT3), calcineurin/nuclear factor of activated T cells (calcineurin/NFAT), nuclear factor-kB/nod-like receptor family pyrin domain containing 3 (NFκB/NLRP3), mitogen-activated protein kinase (MAPK), and the P2Y1 purinoreceptor (P2Y1R) pathways. Here, STAT3 is linked to Alzheimer disease.