AQP4 and brain injury: Reactive astrocytes, induced by brain injuries and disease, undergo a series of molecular, morphological, and functional alterations such as inflammatory factor release (Hasel et al., 2021), glial scar formation (Sofroniew and Vinters, 2010), downregulation of glutamate transporter-1 (GLT-1) expression (Tanaka et al., 1997), and upregulation of water channel protein aquaporin 4 (AQP4; Kitchen et al., 2020).