STAT3 and neurodegenerative disease: The Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) pathway is responsible for the initiation of astrogliosis (Herrmann et al., 2008; Ceyzeriat et al., 2016), and activation of this pathway is a hallmark feature of reactive astrocytes in many animal models of PD and other neurodegenerative diseases (Ben Haim et al., 2015).